Evaluation of Genetic Diversity of Durum Wheat Genotypes (Triticum turgidum var durum) using Agro-morphological Traits for Resistance to Zinc Deficient Stress

10.30486/roce.2018.545281

Abstract

Abstract
 
Micronutrients deficiency stress is one of the most important dangers for increasing the yield and good production of crops in the world. In order to evaluate genetic diversity of nineteen durum wheat (Triticum turgidum var durum) genotypes to identify the most zinc-deficient stress resistant genotypes and also finding the best stress tolerance indices, an experiment was carried out in the University of Maragheh, Iran during cropping season of 2014 by using a factorial design in the randomized complete block design (RCBD) with three replications. The experiment was done zinc deficient stress (non-Zn application; -Zn) and normal soil application (5 mg Zn/kg soil + foliar application with 0.44 g Zn/liter water at stem elongation and grain filling stages; +Zn) conditions. Results indicated that Zn conditions as well as, wheat genotypes differed significantly for all studied agro-morphological traits in both normal and Zn deficient stress conditions. Our findings indicated that Zn-deficient stress significantly decreased the spike length (SL), peduncle length (PedL), penultimate length (PenL), plant height (PH), spike weight (SW), peduncle weight (PedW), penultimate weight (PenW), biological yield (BY), grain yield (GY), harvest index (HI), number of grains per spike (NGS), number of fertile spikelet per spike (FS) and 1000 grains weight (TGW) by 14, 10.6, 10.4, 12.5, 25.3, 26.2, 27.9, 27.5, 29.4, 5.0, 25.5, 17.7 and 5.4%, respectively. Among durum wheat genotypes, ‘G2’ had the highest and also ‘G10’ and ‘G19’ had the lowest SW, PedW, BY and FS, respectively; while the highest and the shortest GY and NGS was observed in ‘G17’ (0.763 g/plant and 23.2 grain) and ‘G10’ and ‘G19’ (0.372 and 367 g/plant and 8.9 and 9.5 grain) genotypes, respectively. This indicating the presence of variability, which can be exploited through selection for further breeding programs. According to results of stress tolerance indices, ‘G17’, ‘G16’ and ‘G3’ genotypes have higher GY and STI index than other genotypes in two Zn conditions and identified as suitable genotypes for production in Zn deficient stress condition.
 
Key words: Agro-morphological traits; Breeding; Calcareous soil; Durum wheat; Genetic variability; Zinc deficit.
 

Keywords


       
 

Original Research

 
   

                 Research on Crop Ecophysiology                                  Vol.13/1, Issue 1 (2018), Pages: 23- 40

 

 

 
 

 

 

 

 

Evaluation of Genetic Diversity of Durum Wheat Genotypes (Triticum turgidum var durum) using Agro-morphological Traits for Resistance to Zinc Deficient Stress

 

Ezatollah Esfandiari1, Majid Abdoli2*, Behzad Sadeghzadeh3

1Department of Plant Production and Genetics, Faculty of Agriculture, University of Maragheh, P.O. Box 55181-83111, Maragheh, Iran

2Young Researchers and Elite Club, Zanjan Branch, Islamic Azad University, Zanjan, Iran

3Dryland Agricultural Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Maragheh, Iran

 

*Corresponding author: majid.abdoli64@yahoo.com;

 

Received:6 August 2017                                           Accepted: 25 December 2017

 

Abstract

 

Micronutrients deficiency stress is one of the most important dangers for increasing the yield and good production of crops in the world. In order to evaluate genetic diversity of nineteen durum wheat (Triticum turgidum var durum) genotypes to identify the most zinc-deficient stress resistant genotypes and also finding the best stress tolerance indices, an experiment was carried out in the University of Maragheh, Iran during cropping season of 2014 by using a factorial design in the randomized complete block design (RCBD) with three replications. The experiment was done zinc deficient stress (non-Zn application; -Zn) and normal soil application (5 mg Zn/kg soil + foliar application with 0.44 g Zn/liter water at stem elongation and grain filling stages; +Zn) conditions. Results indicated that Zn conditions as well as, wheat genotypes differed significantly for all studied agro-morphological traits in both normal and Zn deficient stress conditions. Our findings indicated that Zn-deficient stress significantly decreased the spike length (SL), peduncle length (PedL), penultimate length (PenL), plant height (PH), spike weight (SW), peduncle weight (PedW), penultimate weight (PenW), biological yield (BY), grain yield (GY), harvest index (HI), number of grains per spike (NGS), number of fertile spikelet per spike (FS) and 1000 grains weight (TGW) by 14, 10.6, 10.4, 12.5, 25.3, 26.2, 27.9, 27.5, 29.4, 5.0, 25.5, 17.7 and 5.4%, respectively. Among durum wheat genotypes, ‘G2’ had the highest and also ‘G10’ and ‘G19’ had the lowest SW, PedW, BY and FS, respectively; while the highest and the shortest GY and NGS was observed in ‘G17’ (0.763 g/plant and 23.2 grain) and ‘G10’ and ‘G19’ (0.372 and 367 g/plant and 8.9 and 9.5 grain) genotypes, respectively. This indicating the presence of variability, which can be exploited through selection for further breeding programs. According to results of stress tolerance indices, ‘G17’, ‘G16’ and ‘G3’ genotypes have higher GY and STI index than other genotypes in two Zn conditions and identified as suitable genotypes for production in Zn deficient stress condition.

 

Key words: Agro-morphological traits; Breeding; Calcareous soil; Durum wheat; Genetic variability; Zinc deficit.

 

Abbreviations: Zinc (Zn), Iron (Fe), Randomized complete block design (RCBD), Spike length (SL), Peduncle length (PedL), Penultimate length (PenL), Plant height (PH), Spike weight (SW), Peduncle weight (PedW), Penultimate weight (PenW), Biological yield (BY), Grain yield (GY), Harvest index (HI), Number of grains per spike (NGS), Number of fertile spikelet per spike (FS), 1000 grains weight (TGW), Green coverage (GC), Growth habit (GH), Vigour at tillering stage (Vig.Till), Days to heading (DHE), Days to maturity (DMA), Agronomic score (AS), Stress susceptibility index (SSI), Stress tolerance index (STI), Geometric mean production (GMP), Stress tolerance (TOL), Mean production (MP), Harmonic mean (HARM).

 

Introduction

 

Micronutrients deficiency stress (such as zinc and iron) is one of the most important abiotic stresses in plants and leads to major damage in crop yield as well as plant growing, plant structure and plant metabolism (Cakmak et al., 2010). Also, deficiency of Zn and Fe is a major environmental stress factor limiting wheat productivity around the globe, particularly in countries of Australia, China, India, Pakistan, Turkey and Iran (Cakmak, 2002).

Bread and durum wheat is one of the most important strategic cereal crop in Iran and the world in terms of production and utilization. Durum wheat (Triticum turgidum var durum) is among the most diversified crop species in Iran cultivated on about 200-300 thousand hectares of the across arable lands. The lower yield of durum wheat in Iran is the result of effects of environmental conditions (such as drought, salinity, nutrient deficiencies in the soil, climate change and etc.) and also limited diversity in the genome of wheat, which is used in breeding programs. The identification of micronutrient deficiency-tolerant durum wheat genotypes is the starting point for such breeding studies.

The knowledge about the genetic relationships of genotypes provides useful information to address breeding programmes and germplasm resource management. Genetic diversity is a pre-requisite for crop improvement program to develop the superior recombinants. Various researchers from the world have made investigations on genetic diversity of cereals such wheat, applying molecular (Hailu et al., 2005; Nielsen et al., 2014; Kha et al., 2015; Zeshan et al., 2016), agro-morphology (Hailegiorgis et al., 2011; Dutamo et al., 2015; Sakina et al., 2016; Esfandiari and Abdoli, 2017) and protein quality (Dessalegn et al., 2011) methods. The morphological and agronomic attributes of wheat have been evaluated to measure genetic variation and their close relatives. So that, Abdoli and Esfandiari (2017) reported that there is a large genetic diversity among wheat genotypes and Zn deficient stress significantly decreased the number of grains per spike (NGS), biological yield (BY) and grain yield (GY) by 20.8, 18.6 and 22.1%, respectively. In the meantime, the evaluation of stress resistance indices is of great importance. There are different stress resistance indices such as stress susceptibility index (SSI), stress tolerance index (STI), geometric mean production (GMP), stress tolerance (TOL), mean production (MP), harmonic mean (HARM) and etc (Abdoli and Esfandiari, 2017). In this regard, Gharib-Eshghi et al. (2016) stated that the considering correlation between indices and GY under normal and stress conditions, STI was identified as the best index for selection of drought-tolerant sesame cultivars, which are capable of producing high yields under normal conditions. In that respect, Pozveh and Golparvar (2016) and Bakhtari et al. (2017) reported that STI, GMP and MP indices had the most correlation with the yield, therefore, they were used for screening drought-tolerant varieties. In another study, Molla Heydari Bafghi et al. (2017) reported that according to the analysis of the correlation between GY and tolerance to stress indices (MP, GMP and STI) in terms of the normal and stress conditions, as the best indices for selection of tolerant genotypes were detected. Barati et al. (2017) stated that the high-yielding varieties were more tolerant based on STI index, but the average of yield stability under stressed conditions (YSI) was significantly higher in the wild barley group of genotypes comparing to cultivated ones, indicating a high level of stress tolerance in wild genotypes.

According to the stated cases, the aim of the present study was conducted to determine the effects of zinc deficient on agro-morphological characteristics and to evaluate the genetic diversity and relationships between durum wheat genotypes and selection of the best genotype for grain production, next plant breeding programs and advice to farmers.

 

Materials and Methods

 

Description of the study area and soil characters

 

This study was conducted at the research area of Department of Plant Production and Genetics, University of Maragheh, Maragheh, Iran during the cropping season of 2014. This pot experiment covered the period from the second week of March, 2014 to the third week of July, 2014. The site is at 37° 22ʹ N latitude; 46° 16ʹ E longitude and with elevation of 1542 m above sea level. Long-time average precipitation, temperature and humidity are 309 mm, 13.2 °C and 46%, respectively. Soil characteristics were including: soil texture = clay loam, pH value = 7.2, organic matters = 0.4%, available K2O (K) = 360 mg/kg soil, available P2O5 (P) = 6.1 mg/kg soil, total nitrogen (N) = 0.09% and CaCO3 = 20%.

 

Experimental design and experimental materials

 

The experimental materials consisted of 2 conditions of Zn deficient and 19 genotypes of durum wheat which carried out in a factorial design in the randomized complete block design (RCBD) with three replications. The first factor was two condition of Zn were (1) zinc deficient stress (non-Zn application; -Zn) and (2) normal soil application (5 mg Zn/kg soil + foliar application with 0.44 g Zn/liter water at stem elongation and grain filling stages; +Zn) and also the second factor was nineteen durum wheat genotypes. A total of nineteen durum wheat (Triticum turgidum var durum) genotypes that include two standard checks (Dena and Saji) and seventeen exotic durum wheat were included in this study. The seeds of durum wheat genotypes were obtained from Dryland Agricultural Research Institute (DARI) of Iran. The agronomic traits and growth characteristics of genotypes used in the experiments are shown in Table 1.

Growth conditions and trial management

 

Seeds of each genotype were sown in in plastic pots (PVC) with 20 cm diameter and 30 cm height which filled with 3.5 kg of soil with -Zn and +Zn. Fourteen seeds were sown in each pot and daily watered by deionized water and the seedlings were thinned to seven seedlings per pot at 3 to 4-leaf stage. Recommended fertilizer rate of 200/100 mg/kg N/P in the forms of Calcium nitrate tetrahydrate (Ca(NO3)2.4H2O) and Monopotassium phosphate (KH2PO4) were applied and mixed with soil at the same time during sowing. Weeds were controlled manually and all other agronomic practices were undertaken uniformly to the entire pot.

 

Agronomic traits and morphological characteristics measurements

The observations were recorded on five randomly selected competitive plants from each genotype in each pot on eleven agro-morphological characters viz; spike length (SL), peduncle length (PedL), penultimate length (PenL), plant height (PH), spike weight (SW), peduncle weight (PedW), penultimate weight (PenW), biological yield (BY), grain yield (GY), harvest index (HI), number of grains per spike (NGS), number of fertile spikelet per spike (FS) and 1000 grains weight (TGW). Harvest index (%) was calculated as grain yield / aboveground dry biomass × 100.

 

Zinc deficient resistance indices determination

The responses of wheat genotypes were studied under optimal and limited Zn conditions using common quantitative indices of stress tolerance. Six stress resistance indices including stress susceptibility index (SSI), stress tolerance index (STI), geometric mean production (GMP), stress tolerance (TOL), mean production (MP) and harmonic mean (HARM) were calculated using the following relationships (Fischer and Maurer, 1978; Fernandez, 1992; Rosielle and Hamblin, 1981; Kristin et al., 1997):

SSI = [1- (Ys /Yp)]/SI

 
 

TOL = Yp - Ys

 
 

Where Yp is yield of each genotype in non-stress conditions, Ys is yield of each genotype in Zn deficient stress conditions, Ȳp is mean yield of all genotypes in non-stress conditions, Ȳs is mean yield of all genotypes in Zn deficient stress conditions.

 

 

 

Table 1. Major specifications and features of 19 studied durum wheat genotypes in this research.

Code

Genotypes name/pedigree

GC (%)

GH

Vig.Till

DHE (day)

DMA (day)

AS

PH (cm)

TGW (g)

GY (kg/ha)

G1

Dena (check)

100

S

3

159

183

3

48

36

1593

G2

KC_3426

60

SF

2

162

191

3

66

34

1000

G3

Saji (check)

100

S

5

150

177

4

49

30

2656

G4

Mrb3/Mna-1

70

S

3

150

182

2

50

33

2313

G5

RCOL/THKNEE_2/3/SORA/2*PLATA_12//SOMAT

60

S

3

153

183

3

48

33

2075

G6

GREEN-14//YAV-10/AUK

90

S

4.5

150

180

4

47

29

2238

G7

Bisu-1//CHEN-1/TEZ/3/HUI//CIT71/Cll

100

S

5

150

180

4

50

29

2300

G8

Mrf1/Stj2//Bcrch1

85

S

4

153

183

4

54

31

2444

G9

Gdr2

95

S

5

153

184

5

53

33

3031

G10

Geromtel-1

80

S

4

150

183

5

57

35

3069

G11

Azarbayjan (LR)/Wadalmes IRDW2003-04-140-OMAR-OMAR-OMAR-4MAR-OMAR

90

S

4

153

183

4

59

33

2156

G12

MEXICALI 75

80

S

3

153

185

3

40

35

1825

G13

HYDRANASSA30/SILVER_5/3/AUK/GUIL//GREEN/10/PLATA_10/6/MQUE/4/USDA573//QFN/AA_7/3/ALBA-D/5/AVO/HUI/7/PLATA_13/8/THKNEE_11/9/CHEN/ALTAR 84/3/HUI/POC//BUB/RUFO/4/FNFOOT

80

S

3

155

184

3

47

29

1456

G14

AJAIA_12/F3LOCAL(SEL.ETHIO.135.85)//PLATA_13/3/SOMBRA_20/4/SNITAN/5/SOMAT_4/INTER_8

70

S

2

155

184

2

45

27

1369

G15

AAZ//ALTAR84/ALD/3/AJAIA/4/AJAIA_12/F3LOCAL(SEL.ETHIO.135.85)//PLATA_13/5/SOOTY_9/RASCON_37/9/USDA595/3/D67.3/RABI//CRA/4/ALO/5/HUI/YAV_1/6/ARDENTE/7/HUI/YAV79/8/POD_9

80

S

3

158

187

3

47

31

1469

G16

RASCON_37/2*TARRO_2/3/AJAIA_12/F3LOCAL(SEL.ETHIO.135.85)//PLATA_13/4/SORA/2*PLATA_12//SOMAT_3

60

S

2

158

187

2

53

33

1244

G17

SORA/2*PLATA_12//SOMAT_3/3/STORLOM/4/BICHENA/AKAKI_7

85

S

2

154

183

2

43

34

2000

G18

SHAG_14/ANADE_1//KITTI_1/4/ARMENT//SRN_3/NIGRIS_4/3/CANELO_9.1

70

S

2.5

155

184

3

53

33

1906

G19

VRKS_3/7/ENTE/MEXI_2//HUI/4/YAV_1/3/LD357E/2*TC60//JO69/5/BISU/6/RYPS26_2/10/PLATA_10/6/MQUE/4/USDA573//QFN/AA_7/3/ALBA-D/5/AVO/HUI/7/PLATA_13/8/THKNEE_11/9/CHEN/ALTAR 84/3/HUI/POC//BUB/RUFO/4/FNFOOT

60

S

3

156

185

3

52

32

1769

Green coverage (GC), growth habit (GH), vigour at tillering stage (Vig.Till), days to heading (DHE), days to maturity (DMA), agronomic score (AS), plant height (PH), 1000 grains weight (TGW) and grain yield (GY).

S: Spring, SF: Spring-fall (interstitial).

Source: Dryland Agricultural Research Institute (DARI), Agricultural Research, Education and Extension Organization (AREEO), Maragheh, Iran.

 

Statistical analysis

 

The data were subjected to analysis of variance (ANOVA) by using the SAS software version 8.0 (SAS Institute, 1987). Mean comparison was conducted using Duncan's multiple range test (DMRT) at P < 0.05 (Duncan, 1955). The cluster analysis was done by SPSS software version 16.0.

 

Table 2. Result of analysis of variance of grain yield and agro-morphological traits affected of Zn conditions and durum wheat genotypes.

Source of variation

df

Mean squares (MS)

SL

PedL

PenL

PH

SW

Replication

2

0.931 *

37.6 **

1.27 ns

85.3 *

15644.6 *

Zn conditions (Zn)

1

9.15 **

168.0 **

17.4 **

875.9 **

130901.4 **

Genotypes (G)

18

1.76 **

49.7 **

4.67 **

122.3 **

12409.4 **

Zn × G

18

0.493 *

22.2 **

1.95 **

52.9 **

6731.7 ns

Error

74

0.261

7.38

0.705

23.6

4456.3

CV (%)

-

13.7

12.1

11.7

11.6

28.4

Source of variation

df

PedW

PenW

BY

GY

HI

Replication

2

2414.3 ns

354.7 ns

0.231 ns

0.059 ns

24.1 ns

Zn conditions (Zn)

1

29280.1 **

7537.9 **

3.67 **

0.867 **

155.4 *

Genotypes (G)

18

3202.8 **

1043.6 **

0.271 **

0.080 **

149.3 **

Zn × G

18

1530.4 ns

403.6 *

0.106 ns

0.026 ns

46.7 *

Error

74

1003.0

228.6

0.081

0.021

24.0

CV (%)

-

29.8

30.3

25.3

28.6

11.0

Source of variation

df

NGS

FS

TGW

 

 

Replication

2

22.4 ns

2.75 ns

64.7 **

 

 

Zn conditions (Zn)

1

453.6 **

43.8 **

128.8 **

 

 

Genotypes (G)

18

96.2 **

5.67 **

94.2 **

 

 

Zn × G

18

29.9 ns

2.07 ns

49.7 **

 

 

Error

74

21.2

1.25

12.2

 

 

CV (%)

-

33.5

17.4

9.26

 

 

Spike length (SL), peduncle length (PedL), penultimate length (PenL), plant height (PH), spike weight (SW), peduncle weight (PedW), penultimate weight (PenW), biological yield (BY), grain yield (GY), harvest index (HI), number of grains per spike (NGS), number of fertile spikelet per spike (FS) and 1000 grains weight (TGW).

ns, * and ** are non-significant and significant at 5% and 1% probability levels, respectively.

 

Results

 

Grain yield and agro-morphological traits

 

Analysis of variance (ANOVA) of the 13 agro-morphological traits is presented in Table 2. Significant differences were observed among Zn treatments for all studied of agro-morphological characters (Table 2). The results showed that, there were significant effects among durum wheat genotypes considering all the studied traits (P < 0.01) (Table 2). Also, analysis of variance (Table 2) indicated significant Zn condition × genotype interaction on the traits of SL, PedL, PenL, PH, PenW, HI and TGW. This indicates the existence of considerable genetic variation among the genotypes and thus the possibility of identifying tolerant genotypes to Zn deficient stress within durum wheat germplasm.

The durum wheat genotypes under study showed a wide range of variation both under normal and Zn deficient stress condition (Tables 4 and 5). The results of mean comparisons of the spike length (SL) under non-stress situation showed that, ‘G2’ and ‘G19’ had the highest and lowest value (5.93 and 2.83 cm, respectively). However, under Zn deficient stress condition ‘G2’ and ‘G13’ had the highest (4.80 cm) and lowest (2.67 cm) value, respectively (Table 5). Mean SL was 14.0% lower under Zn-deficient stress than under non-Zn deficient stress (Table 3).

Peduncle length measured for durum wheat genotypes ranged from 19.9 to 33.8 cm (‘G19’ and ‘G11’, respectively), with an average value of 23.6 cm under non-Zn deficient stress conditions, and also from 15.6 to 31.6 cm (‘G13’ and ‘G2’, respectively), with an average value of 21.1 cm, under Zn deficient stress conditions (Table 5). Among durum wheat genotypes, penultimate length varied from 6.07 cm at ‘G7’ to 9.70 cm at ‘G11’, with an average of 7.53 cm under non-Zn deficient stress, and from 5.23 cm at ‘G1’ to 9.30 cm at ‘G2’, with an average of 6.75 cm under Zn deficient stress (Table 5). Our findings indicated that Zn-deficient stress significantly reduced length of peduncle (10.6%) and penultimate (10.4%) internodes (Table 3).

A measurement of plant height (PH) of durum wheat genotypes demonstrated that, under non-stress condition ‘G11’ genotype with mean of 56.8 cm and ‘G19’ genotype with mean of 37.2 cm had the highest and lowest PH, respectively. But, under Zn deficient stress condition ‘G2’ with a mean of 54.8 cm had the highest and ‘G13’ with a mean of 31.3 cm had the lowest PH, respectively (Table 5). Also, Zn-deficient stress decreased PH by 12.2% (Table 3).

Results through the mean comparisons showed that, the highest and the lowest spike weight were related to ‘G2’ (355 mg) and ‘G10’ (172 mg), respectively (Table 4). Among durum wheat genotypes, ‘G2’ with a mean of 178 mg had the highest and also ‘G10’, ‘G1’ and ‘G19’ with a mean of 85, 83 and 80 mg had the lowest peduncle weight, respectively (Table 4). Penultimate weight measured for durum wheat genotypes ranged from 33 to 115 mg (G19 and G2, respectively), with an average value of 58 mg under non-Zn deficient stress conditions, and also from 22 to 82 mg (‘G1’ and ‘G2’, respectively), with an average value of 41.8 mg, under Zn deficient stress conditions (Table 5). Also, Zn-deficient stress decreased weight of spike, peduncle and penultimate internodes by 25.3, 26.2 and 27.9%, respectively (Table 3).

The study on biological yield (BY) trait showed that, ‘G2’ had the highest mean (1.57 g/plant) while ‘G5’, ‘G19’ and ‘G10’ had the lowest one (0.91, 0.88 and 0.83 g/plant) considering BY (Table 4). The ‘G17’ had the maximum mean of grain yield (GY, 0.763 g/plant) while ‘G5’, ‘G10’ and ‘G9’ had the minimum mean (0.381, 0.372 and 0.367 g/plant, respectively) (Table 4). Increase or decrease of this trait can be due to variety of yield components and different response to environmental conditions. Our findings indicated that Zn-deficient stress significantly decreased the BY per plant and GY per plant by 27.5 and 29.4%, respectively (Table 3). The present study showed significant correlation between GY and several of the agro-morphological traits known to be components determining the yield, including SL, SW, BY, HI, NGS and FS under normal (non-Zn deficient stress) condition and SL, PedL, PH, SW, PedW, PenW, BY, HI, NGS and FS under Zn deficient stress condition (Table 6).

In this study, harvest index (HI) measured for durum wheat genotypes ranged from 30.3 to 56.2% (‘G2’ and ‘G17’, respectively), with an average value of 45.6% under non-Zn deficient stress conditions, and also from 27.2 to 49.5% (‘G5’ and ‘G17’, respectively), with an average value of 43.3%, under Zn deficient stress conditions (Table 5). So that, HI was thus 5.0% lower under Zn-deficient stress than non-Zn deficient stress condition (Table 3).

The results demonstrated that, the highest and the shortest number of grains per spike (NGS) was observed in ‘G17’ genotype (23.2 grain) and ‘G10’ genotype (8.9 grain), respectively (Table 4). In the present study, ‘G2’ and ‘G3’ with a mean of 8.17 and 8.12 had the highest and also ‘G12’, ‘G11’ and ‘G10’ with a mean of 5.55, 5.18 and 4.92 had the lowest number of fertile spikelet per spike (FS), respectively (Table 4). Zinc deficient stress also decreased the NGS and FS by 25.5 and 17.7%, respectively (Table 3).

A measurement of 1000 grains weight (TGW) demonstrated that, under non-stress condition ‘G8’ genotype with mean of 45.4 g and ‘G14’ genotype with mean of 29.4 g had the highest and lowest TGW, respectively. But, under Zn deficient stress condition ‘G7’ with a mean of 45.1 g had the highest and also ‘G18’ and ‘G2’ with a mean of 27.6 and 27.5 g had the lowest TGW, respectively (Table 5). Also, Zn-deficient stress reduced TGW by 5.4% (Table 3).

 

Table 3. The average values of the studies agro-morphological traits under normal and zinc deficient stress conditions and the percentage change of each trait after the stress treatment in durum wheat.

Traits

Conditions

Percentage change

(%)

Normal

(non-stress)

Zinc deficient stress

Spike length (cm)

3.99 a

3.43 b

-14.0

Peduncle length (cm)

23.6 a

21.1 b

-10.6

Penultimate length (cm)

7.53 a

6.75 b

-10.4

Plant height (cm)

44.7 a

39.1 b

-12.5

Spike weight (mg)

268.5 a

200.7 b

-25.3

Peduncle weight (mg)

122.0 a

90.0 b

-26.2

Penultimate weight (mg)

58.0 a

41.8 b

-27.9

Biological yield (g/plant)

1.31 a

0.95 b

-27.5

Grain yield (g/plant)

0.596 a

0.421 b

-29.4

Harvest index (%)

45.6 a

43.3 b

-5.0

Number of grains per spike

15.7 a

11.7 b

-25.5

Number of fertile spikelet per spike

7.02 a

5.78 b

-17.7

1000 grains weight (g)

38.8 a

36.7 b

-5.4

Similar letters in each row show non-significant difference at 5% level in Duncan's multiple rang test.

 

 

 

 

Table 4. Mean comparison of some of agro-morphological traits in durum wheat genotypes.

Genotypes code

SW

(mg)

PedW

(mg)

BY

(g/plant)

GY

(g/plant)

NGS

FS

G1

195 cd

83 d

1.03 c-f

0.540 b-f

13.2 c-g

6.08 c-e

G2

355 a

178 a

1.57 a

0.477 d-f

16.3 b-e

8.17 a

G3

276 a-c

138 b

1.38 a-d

0.674 a-c

17.7 a-d

8.12 a

G4

205 cd

100 b-d

1.05 c-f

0.489 c-f

11.6 d-g

6.45 b-e

G5

201 cd

101 b-d

0.91 f

0.381 f

10.4 e-g

5.72 de

G6

225 b-d

99 b-d

1.04 c-f

0.468 d-f

10.9 e-g

6.18 c-e

G7

239 b-d

97 b-d

1.08 b-f

0.489 c-f

11.3 e-g

6.10 c-e

G8

240 b-d

112 b-d

1.20 a-f

0.542 b-f

12.5 c-g

6.40 b-e

G9

201 cd

93 cd

0.99 d-f

0.434 d-f

10.9 e-g

5.95 de

G10

172 d

85 d

0.83 f

0.372 f

8.9 g

4.92 e

G11

192 cd

109 b-d

0.97 ef

0.411 ef

11.1 e-g

5.18 e

G12

231 b-d

90 cd

1.03 c-f

0.429 d-f

10.4 e-g

5.55 e

G13

212 cd

90 cd

1.07 c-f

0.490 c-f

15.6 b-f

5.78 de

G14

304 ab

95 b-d

1.22 a-f

0.597 a-e

18.2 a-c

7.17 a-d

G15

262 b-d

130 bc

1.36 a-e

0.619 a-d

17.7 a-d

7.20 a-d

G16

271 bc

113 b-d

1.45 ab

0.705 ab

19.7 ab

7.75 ab

G17

267 bc

118 b-d

1.42 a-c

0.763 a

23.2 a

7.50 a-c

G18

220 b-d

105 b-d

1.00 d-f

0.418 ef

12.0 d-g

5.80 de

G19

191 cd

80 d

0.88 f

0.367 f

9.5 fg

5.60 e

Spike weight (SW), peduncle weight (PedW), biological yield (BY), grain yield (GY), number of grains per spike (NGS) and number of fertile spikelet per spike (FS).

Similar letters in each column show non-significant difference at 5% level in Duncan's multiple rang test.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 5. Comparison of the mean interactions of Zn conditions × genotypes on some of agro-morphological traits in durum wheat genotypes under non-stress and zinc deficient stress conditions.

Treatments

SL (cm)

PedL (cm)

PenL (cm)

PH (cm)

PenW (mg)

HI (%)

TGW (g)

Zn conditions

Genotypes code

Normal

(non-stress)

G1

3.90 b-j

24.7 c-g

7.67 c-f

44.4 c-h

50 c-j

53.2 ab

43.3 a-d

G2

5.93 a

25.8 cd

9.60 a

50.6 a-d

115 a

30.3 ef

32.1 h-l

G3

4.70 bc

25.1 c-f

7.87 b-e

48.1 a-e

63 b-f

49.0 a-c

39.6 a-g

 

G4

3.90 b-j

20.2 e-k

6.90 d-i

38.6 e-l

45 c-j

47.1 a-c

41.3 a-f

 

G5

3.90 b-j

23.8 c-h

8.90 a-c

42.6 c-j

64 b-e

47.6 a-c

38.5 a-h

 

G6

4.53 b-d

22.1 c-j

6.83 d-j

42.6 c-j

57 b-h

44.5 b-d

45.0 a-c

 

G7

3.47 e-m

20.1 e-k

6.07 f-j

38.8 e-l

44 c-j

46.3 b-d

41.4 a-f

 

G8

3.83 b-k

21.9 c-j

7.63 c-j

45.6 c-g

56 b-h

44.9 b-d

45.4 a

 

G9

3.40 f-m

19.6 g-k

6.50 e-j

38.9 e-l

49 c-j

43.4 b-d

41.2 a-f

 

G10

3.60 d-m

22.6 c-j

6.90 d-i

41.6 c-k

50 c-j

44.6 b-d

42.0 a-e

 

G11

3.77 c-l

33.8 a

9.70 a

56.8 a

71 bc

41.3 cd

34.8 f-k

 

G12

3.60 d-m

23.2 c-i

7.20 d-h

43.6 c-h

54 b-i

41.3 cd

42.6 a-e

 

G13

4.17 b-h

25.5 c-e

8.40 a-d

50.7 a-d

68 b-d

46.1 b-d

31.6 i-l

 

G14

3.90 b-j

23.2 c-i

7.23 d-h

45.2 c-g

49 c-j

49.7 a-c

29.4 kl

 

G15

4.27 b-g

27.3 bc

7.40 c-g

51.2 a-c

62 b-f

43.4 b-d

38.5 a-h

 

G16

4.33 b-f

24.3 c-g

7.60 c-g

46.1 b-g

59 b-g

49.7 a-c

32.4 h-l

 

G17

4.43 b-e

22.0 c-j

6.83 d-j

43.3 c-h

57 b-h

56.2 a

38.1 b-i

 

G18

3.40 f-m

22.4 c-j

7.63 c-g

42.8 c-i

56 b-h

41.4 cd

42.6 a-e

 

G19

2.83 k-m

19.9 f-k

6.27 e-j

37.2 g-l

33 f-j

46.4 b-d

37.8 d-i

Zinc deficient stress

G1

2.80 lm

18.0 i-k

5.23 j

32.0 kl

22 j

48.7 a-c

35.7 e-k

G2

4.80 b

31.6 ab

9.30 ab

54.8 ab

82 b

30.9 ef

27.5 l

G3

4.00 b-i

24.1 c-g

7.50 c-g

42.8 c-i

56 b-h

48.7 a-c

36.5 d-j

 

G4

3.60 d-m

21.0 d-j

7.70 c-f

39.9 e-l

52 c-j

45.0 b-d

42.5 a-e

 

G5

3.03 i-m

17.3 jk

5.70 h-j

32.9 j-l

27 h-j

27.2 f

31.9 h-l

 

G6

3.30 g-m

18.5 h-k

5.30 ij

33.5 i-l

31 g-j

45.0 b-d

40.3 a-f

 

G7

4.07 b-h

20.6 d-k

5.47 ij

38.4 e-l

45 c-j

44.2 b-d

45.1 ab

 

G8

3.20 h-m

22.7 c-j

7.33 c-h

41.2 d-k

43 c-j

45.5 b-d

40.9 a-f

 

G9

2.83 k-m

21.1 d-j

6.77 d-j

37.3 g-l

39 d-j

44.9 b-d

37.9 d-i

 

G10

2.80 lm

18.5 h-k

5.97 g-j

34.7 h-l

27 h-j

43.9 b-d

40.0 a-f

 

G11

3.20 h-m

24.7 c-g

7.87 b-e

42.4 c-j

37 e-j

43.4 b-d

38.0 c-i

 

G12

3.23 h-m

18.6 h-k

5.70 h-j

35.1 h-l

28 h-j

41.6 cd

39.9 a-g

 

G13

2.67 m

15.6 k

5.97 g-j

31.3 l

25 ij

40.3 cd

29.9 j-l

 

G14

3.30 g-m

20.2 e-k

7.47 c-g

39.6 e-l

50 c-j

48.1 a-c

38.7 a-h

 

G15

3.50 e-m

24.6 c-g

7.20 d-h

44.2 c-h

42 c-j

48.9 a-c

33.1 g-l

 

G16

4.27 b-g

23.5 c-h

7.33 c-h

47.2 b-f

55 b-i

47.7 a-c

41.2 a-f

 

G17

3.83 b-k

20.9 d-k

6.03 f-j

39.2 e-l

44 c-j

49.5 a-c

32.0 h-l

 

G18

2.97 j-m

22.1 c-j

6.93 d-i

39.1 e-l

38 d-j

41.9 cd

27.6 l

 

G19

3.70 c-l

17.9 i-k

7.50 c-g

37.9 f-l

52 c-j

36.9 de

38.6 a-h

Spike length (SL), peduncle length (PedL), penultimate length (PenL), plant height (PH), penultimate weight (PenW), harvest index (HI) and 1000 grains weight (TGW).

Similar letters in each column show non-significant difference at 5% level in Duncan's multiple rang test.

 

Table 6. Correlation coefficient of grain yield and agro-morphological traits in durum wheat genotypes under non-stress and zinc deficient stress conditions.

Correlation coefficient of grain yield and agro-morphological traits in normal (non-zinc deficient stress) condition.

Traits

SL

PedL

PenL

PH

SW

PedW

PenW

BY

GY

HI

NGS

FS

TGW

SL

1

                       

PedL

0.35

1

                     

PenL

0.53*

0.80**

1

                   

PH

0.53*

0.93**

0.79**

1

                 

SW

0.89**

0.36

0.56*

0.59**

1

               

PedW

0.83**

0.71**

0.79**

0.82**

0.84**

1

             

PenW

0.84**

0.55*

0.80**

0.68**

0.85**

0.89**

1

           

BY

0.86**

0.44

0.54*

0.66**

0.92**

0.80**

0.72**

1

         

GY

0.46*

0.21

0.14

0.35

0.46*

0.34

0.13

0.74**

1

       

HI

-0.28

-0.24

-0.43

-0.29

-0.37

-0.43

-0.62**

-0.06

0.62**

1

     

NGS

0.50*

0.32

0.29

0.48*

0.50*

0.40

0.29

0.74**

0.86**

0.43

1

   

FS

0.87**

0.26

0.43

0.48*

0.81**

0.68**

0.61**

0.92**

0.77**

0.10

0.78**

1

 

TGW

-0.35

-0.42

-0.45

-0.48*

-0.31

-0.34

-0.42

-0.39

-0.23

0.07

-0.68**

-0.41

1

Correlation coefficient of grain yield and agro-morphological traits in zinc deficient stress condition.

Traits

SL

PedL

PenL

PH

SW

PedW

PenW

BY

GY

HI

NGS

FS

TGW

SL

1

                       

PedL

0.69**

1

                     

PenL

0.53*

0.79**

1

                   

PH

0.80**

0.95**

0.84**

1

                 

SW

0.75**

0.56*

0.55*

0.70**

1

               

PedW

0.81**

0.88**

0.70**

0.88**

0.70**

1

             

PenW

0.87**

0.79**

0.83**

0.89**

0.81**

0.89**

1

           

BY

0.85**

0.70**

0.54*

0.82**

0.86**

0.83**

0.83**

1

         

GY

0.62**

0.48*

0.31

0.58**

0.73**

0.59**

0.56*

0.90**

1

       

HI

-0.07

-0.02

-0.15

-0.03

0.18

-0.05

-0.11

0.31

0.65**

1

     

NGS

0.59**

0.55*

0.33

0.60**

0.65**

0.69**

0.55*

0.86**

0.89**

0.45

1

   

FS

0.81**

0.63**

0.52*

0.74**

0.85**

0.81**

0.82**

0.94**

0.85**

0.29

0.80**

1

 

TGW

0.04

-0.23

-0.18

-0.15

0.07

-0.25

-0.08

0.03

0.16

0.40

-0.27

0.00

1

                                       

Spike length (SL), peduncle length (PedL), penultimate length (PenL), plant height (PH), spike weight (SW), peduncle weight (PedW), penultimate weight (PenW), biological yield (BY), grain yield (GY), harvest index (HI), number of grains per spike (NGS), number of fertile spikelet per spike (FS) and 1000 grains weight (TGW).

* ,** Significantly different at 5% and 1% probability levels, respectively.

 

Zinc resistance indices

In this research, most of stress tolerance indices such as stress susceptibility index (SSI), stress tolerance index (STI), geometric mean production (GMP), stress tolerance (TOL), mean production (MP) and harmonic mean (HARM) based on grain yield (GY) were calculated in two different Zn conditions (Table 7). The stress index values of the durum wheat genotypes are shown in Table 7. The stress intensity (SI) calculated over the GY of 19 durum wheat genotypes under Zn deficient stress was identified as 0.294 (Table 7).

The grain yield (GY) quantities of the durum wheat genotypes produced under normal (non-Zn deficient stress) conditions varied between 0.397 and 0.854 g/plant, and the values under Zn-deficient stress conditions varied between 0.148 and 0.686 g/plant (Table 7). According to Table 7, the genotypes ‘G17’, ‘G3’, ‘G1’, ‘G16’ and ‘G13’ had the greatest GY under normal conditions (0.854, 0.753, 0.749, 0.724 and 0.713 g/plant, respectively), the lowest values were observed in the ‘G19’, ‘G9’ and ‘G10’ genotypes (0.397, 0.455 and 0.459 g/plant, respectively). While the ‘G16’, ‘G17’ and ‘G3’ genotypes yielded the greatest GY under stress conditions (0.686, 0.672 and 0.595 g/plant, respectively), the lowest value was observed in the ‘G5’, ‘G13’ and ‘G10’ genotypes (0.148, 0.267 and 0.285 g/plant, respectively) (Table 7).

Evaluation of stress tolerance index (TOL) of studied genotypes showed that, genotypes with good tolerance to Zn deficient stress didn’t have high potential yield (Table 7). Based on the results ‘G7’ had the lowest TOL and it produced desirable yield under Zn deficient stress conditions. In addition, ‘G7’ had the lowest amount of stress susceptibility index (SSI) (Table 7).

Alternatively, genotypes of ‘G5’, ‘G10’ and ‘G19’ had the lowest amount for four indices of STI, GMP, MP and HARM. In addition, ‘G5’ genotype had high values for SSI and TOL indices. Therefore genotypes of ‘G5’, ‘G10’ and ‘G19’ are can be introduced as sensitive genotypes to Zn deficient stress (Table 7). The results of this study showed that the GMP, MP, HARM and STI indices identified the Zn-deficient tolerant genotypes, and the TOL and SSI indices were able to separate sensitive durum wheat genotypes.

The correlation coefficients among the various indices are presented in Table 8. The results of correlation coefficient indicated that there were highly significant differences between the genotypes for Yp and Ys with STI (r = 0.77** and 0.93**, respectively), GMP (r = 0.76** and 0.94**, respectively), MP (r = 0.85** and 0.88**, respectively) and HARM (r = 0.67** and 0.97**, respectively) (Table 8).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 7. Assessed zinc resistance indices from grain yield data for studied durum wheat genotypes.

Genotypes code

Yp

Ys

SSI

STI

GMP

TOL

MP

HARM

G1

0.749

0.332

1.898

0.699

0.498

0.417

0.540

0.460

G2

0.525

0.429

0.622

0.635

0.475

0.096

0.477

0.473

G3

0.753

0.595

0.717

1.261

0.669

0.159

0.674

0.665

G4

0.528

0.449

0.514

0.667

0.487

0.080

0.489

0.485

G5

0.613

0.148

2.584

0.256

0.301

0.465

0.381

0.238

G6

0.579

0.357

1.305

0.583

0.455

0.222

0.468

0.442

G7

0.496

0.482

0.096

0.672

0.489

0.014

0.489

0.489

G8

0.635

0.449

0.997

0.804

0.534

0.186

0.542

0.526

G9

0.455

0.413

0.319

0.529

0.433

0.043

0.434

0.433

G10

0.459

0.285

1.293

0.369

0.362

0.174

0.372

0.352

G11

0.496

0.327

1.159

0.456

0.403

0.169

0.411

0.394

G12

0.526

0.332

1.255

0.491

0.418

0.194

0.429

0.407

G13

0.713

0.267

2.130

0.536

0.436

0.446

0.490

0.388

G14

0.674

0.520

0.777

0.986

0.592

0.154

0.597

0.587

G15

0.671

0.567

0.528

1.070

0.616

0.104

0.619

0.614

G16

0.724

0.686

0.177

1.399

0.705

0.038

0.705

0.705

G17

0.854

0.672

0.727

1.616

0.758

0.182

0.763

0.752

G18

0.474

0.362

0.807

0.483

0.414

0.112

0.418

0.410

G19

0.397

0.336

0.529

0.375

0.365

0.062

0.367

0.364

Max

0.854

0.686

2.584

1.616

0.758

0.465

0.763

0.752

Min

0.397

0.148

0.096

0.256

0.301

0.014

0.367

0.238

Mean

0.596

0.421

0.970

0.731

0.495

0.175

0.509

0.483

SI

0.294

 

 

 

 

 

 

 

Grain yield of any genotype under non-stress conditions (Yp), grain yield of any genotype under zinc deficient stress conditions (Ys), stress susceptibility index (SSI), stress tolerance index (STI), geometric mean production (GMP), stress tolerance (TOL), mean production (MP), harmonic mean (HARM) and stress intensity (SI).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 8. Correlation coefficient between studied zinc resistance indices in durum wheat genotypes under non-stress and zinc deficient stress conditions.

Indices

Yp

Ys

SSI

STI

GMP

TOL

MP

HARM

Yp

1

             

Ys

0.51*

1

           

SSI

0.21

-0.73**

1

         

STI

0.77**

0.93**

-0.44

1

       

GMP

0.76**

0.94**

-0.47*

0.99**

1

     

TOL

0.41

-0.58**

0.97**

-0.25

-0.28

1

   

MP

0.85**

0.88**

-0.33

0.99**

0.99**

-0.13

1

 

HARM

0.67**

0.97**

-0.57*

0.98**

0.99**

-0.39

0.96**

1

Grain yield of any genotype under non-stress conditions (Yp), grain yield of any genotype under zinc deficient stress conditions (Ys), stress susceptibility index (SSI), stress tolerance index (STI), geometric mean production (GMP), stress tolerance (TOL), mean production (MP) and harmonic mean (HARM).

* ,** Significantly different at 5% and 1% probability levels, respectively.

 

Discussion

 

In this study, morphological data analysis of the durum wheat genotypes was to investigate the genetic relationships among nineteen durum wheat genotypes. The durum wheat genotypes under study showed a wide range of variation for grain yield (GY) and agro-morphological traits both under normal and Zn deficient stress condition (Tables 4 and 5). These results are in agreement with the findings of Abdoli and Esfandiari (2017) who reported differential response of durum wheat genotypes under Zn deficient stress. Similarly, researches of Kalimullah et al. (2012) and Dutamo et al. (2015) reported that number of grains per spike (NGS), number of tillers per plant, 1000 grains weight (TGW) and GY per plant showed significant differences between various bread wheat genotypes were studied.

Micronutrients deficiency stress (such as Zn and Fe) is the most significant constraint for agricultural production in arid and semi-arid regions. Thus, genetically improved stress tolerant varieties are needed for the future. Our findings indicated that Zn-deficient stress significantly decreased the all agronomic and morphological traits especially GY per plant (Table 3). Our results also showed a reduction in plant height (PH) of durum wheat genotypes under Zn-deficient stress that resulted in the reduced length of peduncle and penultimate internodes (Table 5). Abdoli and Esfandiari (2017) also reported significant reduction in PH and dry matter under Zn deficient stress in 15 durum wheat genotypes. In the present study, NGS was highly affected by Zn deficiency condition than TGW. The losses in GY per plant, TGW, number of fertile spikelet per spike (FS) and NGS at Zn deficiency stress reached 29.4, 5.4, 17.7 and 25.5% (Table 3). It is stated in this regard, decrease in TGW and even the number of fertile spikelet per plant are other reasons for the reduction of GY of cereals under different stress conditions (Guolan et al., 2010). Furthermore, Esfandiari and Abdoli (2017) reported that the Zn deficient stress decreased the NGS, FS, TGW, BY, GY and harvest index (HI) in durum wheat by 29.2, 15.5, 5.1, 24.1, 32.5 and 10.5%, respectively.

The existence of genetic diversity is of great importance in improving wheat traits and developing strategies for optimal conservation of germplasm. Progress in plant breeding is facilitated by accurate information about genetic structure and diversity. The present study provided a detailed understanding of high genetic diversity in the durum wheat genotypes. Zn-deficient is one of the major production constraints in wheat. Development and planting of Zn-deficient tolerant wheat genotypes can reduce yield losses due to Zn deficiency. Four durum wheat genotypes including ‘G3’, ‘G15’, ‘G16’ and ‘G17’ were found Zn-deficient tolerant. ‘G5’, ‘G10’ and ‘G19’ genotypes were sensitive to Zn deficiency (Tables 4, 5 and 7). Abdoli and Esfandiari (2017) reported that the GY of tolerant durum wheat genotypes was significantly higher than the sensitive durum wheat genotypes. Furthermore, they found that the NGS, SL and biomass of tolerant genotypes was significantly higher than the sensitive genotypes and recommended using these traits for identification of tolerant wheat genotypes under Zn deficient stress. We found strong positive correlation between different yield components such as NGS and GY. Also, we found strong positive correlation between different agro-morphological traits such as length of spike, peduncle and penultimate, and PH and their dry weights (Table 6). Similar results of significant correlation between PH and plant biomass have been previously reported (Bhowmik et al. 2009, Mansuri et al. 2012; Esfandiari and Abdoli). In contrast, Saeidi et al. (2016) reported that the high negative significant correlation between GY and length of penultimate internode and also between biomass and HI under both non-stress and stress conditions. In present study, total dry biomass showed a greater reduction in sensitive genotypes than tolerant genotypes. The sensitive genotypes exhibited various symptoms of Zn deficient stress injury such as yellowing of leaf and reduction in shoot growth (data not shown).

Various stress indices were developed and used for the selection of stress-tolerant genotypes by measuring plant yield under stress and taking normal conditions into account (Fischer and Maurer, 1978; Rosielle and Hamblin, 1981; Fernandez, 1992; Saeidi et al., 2016; Krishnamurthy et al., 2016; Abdoli and Esfandiari, 2017). Results showed that a correlation between Zn resistance indices (such as STI, GMP, MP and HARM) and GY was positive (Table 8). Therefore, indices of STI, GMP, MP, and HARM were the best indices for identification of high yielding lines in both conditions (Zn deficient stress tolerant-genotypes). The STI, GMP, MP and HARM indices indicated that ‘G3’, ‘G15’, ‘G16’ and ‘G17’ genotypes could be prominent sources to develop Zn deficiency stress-tolerance (Table 7). According to the results of this research, Abarshahr et al. (2011) stated that the four indices of STI, GMP, MP and HARM had the most correlation with the yield, therefore, they were used for screening drought-tolerant varieties. In addition, Azizi-Chakherchaman et al. (2008) and Saeidi et al. (2016) indicated that indices MP, HARM, GMP and STI are considered as the best indices of lentil and wheat genotypes response with stress intensity of under drought stress. Krishnamurthy et al. (2016) indicated that the GMP and STI indices identified the salt-tolerant genotypes, and the TOL and SSI indices were able to separate sensitive rice genotypes. Also, Chaeikar et al. (2008) stated that MP, GMP, HARM, STI and RWC indices had a positive and significant correlation with yield in stress and non-stress environments and would be suitable indices in both environments for selection of drought-tolerant rice genotypes. Furthermore, Ekbic et al. (2017) reported that the tolerant genotypes had positive correlations with stress tolerance indices of MP, GMP and STI. The Zn-deficient tolerant genotypes identified in this study may prove useful in the development of Zn-deficient tolerant durum wheat genotypes in the adapted genetic background.

 

Conclusions

In conclusion, the results of this research showed that highly significant differences were observed among the wheat genotypes for grain yield and agro-morphological traits under both normal and limited Zn conditions and stress tolerance indices. In general, results of the present study indicated that Zn-deficient stress significantly decreased grain yield and agro-morphological traits. Under the two Zn conditions, durum wheat genotypes of ‘G17’ and ‘G16’ produced the highest and genotypes of ‘G5’, ‘G10’ and ‘G19’ produced the lowest grain yield, number of grains per spike and harvest index, respectively. Results showed that a correlation between Zn resistance indices (such as STI, GMP, MP and HARM) and grain yield was positive. In other words results revealed that yield and studied agro-morphological traits react to Zn stress condition, therefor these traits could be useful and effective for screening wheat tolerant genotypes. Interestingly, the superior genotypes in this study were ‘G2’ and ‘G17’ genotypes which are recommended as the best genotypes for regions suffering from Zn deficient as geemplasm for breeding program.

 

Conflict of interests

The authors have not declared any conflict of interests.

 

Acknowledgements

The authors gratefully acknowledge the financial and technical support of the University of Maragheh, Maragheh, Iran.

 

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