Assessment of terminal drought tolerance among elite wheat (Triticum aestivum L.) genotypes using selected agronomic and physiological traits

ABSTRACT

The selection response of wheat (Triticum aestivum L.) under water-limited condition can be enhanced through breeding novel genotypes possessing drought-adaptive and yield-related agronomic and physiological traits. The objective of this study was to evaluate terminal drought tolerance among bread wheat genotypes and select superior parents for breeding. Agronomic and physiological responses of 28 wheat lines were assessed under well-watered (WW) and terminal drought (TD) treatments using a 7?×?4 alpha-lattice design under rainout shelter (RS) and glasshouse (GH) environments. Significant (p?≤?0.05) genotype?×?environment interaction effects were observed for number of days to heading (DTH), number of days to maturity (DTM), number of productive tillers per plant (TN), grain yield (GY), thousand kernel weight (TKW), stomatal conductance (SC), leaf canopy temperature (LCT) and chlorophyll content index (CCI) suggesting varied genotypic response under WW and TD treatments. Correlation analysis revealed significant associations TN and GY (r?=?0.67; p?≤?0.001), TKW and GY (r?=?0.72; p?≤?0.001), CCI and GY (r?=?0.39; p?≤?0.05) under TD treatment. Drought tolerant wheat genotypes such as LM100, LM72, LM22 and LM95 are useful for direct cultivation and for developing breeding populations with enhanced yield performance.     

Response of selected drought tolerant wheat (Triticum aestivum L.) genotypes for agronomic traits and biochemical markers under drought-stressed and non-stressed conditions

ABSTRACT

Genetic improvement of wheat for drought tolerance can be achieved by developing suitable ideotypes with enhanced yield-response associated with agronomic traits and biochemical markers. The objective of this study was to determine drought response of elite drought tolerant wheat genotypes using agronomic and biochemical traits to select promising lines for breeding. Fourteen wheat genotypes selected from the International Maize and Wheat Improvement Center’s heat and drought tolerance nursery and one standard check variety were evaluated under drought-stressed (DS) and non-stressed (NS) conditions using a randomised complete block design in three replications. Significant (P?<?0.05) genotype, drought condition and genotype?×?drought condition interaction effect were detected for the tested traits suggesting differential response of genotype for selection. Grain yield positively correlated with sucrose (r?=?0.58; P?<?0.05), fructose (r?=?0.52; P?<?0.05) and total sugar (r?=?0.52; P?<?0.05) contents under NS condition and with sucrose (r?=?0.80; P?<?0.001), total sugar (r?=?0.84; P?<?0.001) content, proline content (r?=?0.74; P?<?0.001) and number of grains per spike (r?=?0.58; P?<?0.05) under DS condition. Genetically unrelated wheat genotypes such as SM04, SM19, SM29, SM32, SM45 and SM97 possessing key agronomic and biochemical traits were selected for cultivar development for drought-stressed environments.     

Genotype-by-environment interaction of elite heat and drought tolerant bread wheat (Triticum aestivum L.) genotypes under non-stressed and drought-stressed conditions

ABSTRACT

The selection of relatively high and stable yielding genotypes is key in wheat breeding programs to improve yield performance under heat and drought-stressed environments. This study determined grain yield response and stability among elite heat and drought tolerant bread wheat genotypes under simulated drought-stressed (DS) and non-stressed (NS) environments to select promising parents for breeding. Twenty-four elite bread wheat genotypes selected from the International Maize and Wheat Improvement Centre (CIMMYT) drought and heat tolerant nursery were assessed under NS and DS conditions using a 7?×?4 alpha-lattice design under rainout shelter (RS) and glasshouse (GH) environments. Grain yield data was subjected to analysis of variance (ANOVA), the additive main effect and multiplicative interaction (AMMI) and genotype and genotype-by-environment (GGE) biplot analyses. ANOVA and AMMI revealed highly significant (p?≤?0.001) differences among test genotypes (G), environments (E) and G?×?E interaction effects suggesting differential responses for selection. The GGE biplot explained 83.76% of total variation and aided in selection of high-yielding and stable heat and drought tolerant wheat genotypes such as LM13, LM22, LM95 and LM100. These selections are recommended for breeding for yield gains under heat and drought-stressed environments.     

Genetic variability and estimates of heritability in sorghum (Sorghum bicolor L.) genotypes grown in a semiarid zone of Sudan

A field experiment was conducted to evaluate nine genotypes of sorghum grown for two consecutive cropping seasons in 2006 and 2007 under rain-fed conditions in a semiarid zone at the Research Farm of El Fasher Research Station, Sudan. The objective of the study was to assess genetic variability and heritability among sorghum genotypes using phenotypic morphological traits. A randomized complete block design with four replications was used for the experiment. The grain yield (kg ha^?1), the number of heads/plant, followed by straw yield (kg ha^?1) had the highest genotypic coefficients of variation in both seasons. High heritability (above 95%) was shown for plant height in both seasons. High genetic advance was reported in straw yield, 1000-grain weight and days to flowering in both seasons. Highly significant differences among genotypes were found for all characters. The high-yielding genotype was Adv-Edo-CWS (E-9) with grain yields of 2780.6 kg ha^?1. Grain yield was significantly and positively correlated with straw yield (r = 0.91), number of heads/plant (r = 0.69), plant height (r = 0.53) and 1000-grain weight (r = 0.36). However, it was significantly and negatively correlated with days to 50% flowering (r = ?0.21). Based on their positive association with grain yield, the character’s straw weight, number of heads/plant, plant height and 1000-grain weight would be the preferable selection criteria for sorghum improvement program in the country.     

Agronomic evaluation and identification of potential cowpea (Vigna unguiculata L. Walp) genotypes in South Africa

Cultivar development of cowpea with increased grain yield depends on evaluation and selection of genetically unique and complementary breeding lines. The objective of this study was to evaluate cowpea collections using agronomic traits to select promising parents to develop breeding population. Twenty-two cowpea genotypes were field evaluated using a randomised complete block design with three replications in two locations in South Africa. Analysis of variance revealed significant genotypic (G) and locations (L) differences for all agronomic traits evaluated. Significant differences were also observed for most of the traits due to G X L, G X Year (Y), L X Y and G X L X Y interactions effects. The genotypes tested at two locations showed considerable genetic variation for the following agronomic traits that varied for number of leaves (NL) (20.08–179.78), leaf length (LL) (12.36–67.72 cm), leaf width (LW) (4.78–22.02 cm), number of branches (NB) (6.81–13.85), number of pods per plant (NPPP) (14.33–54.04), number of seeds per pod (NSPP) (11.7286.28), pod diameter (PD) (5.75–22.73 mm), plant height (PH) (6.57–233.71 cm), pod length (PL) (3.94–100.92 mm), hundred seed weight (HSWt) (8.11–49.52 g) and grain yield (GY) (0.10-1.48 t ha^?1). Grain yield was significant and positively correlated with all of the traits except leaf length. The principal component analysis (PCA) identified four principal components (PCs) contributing to 73.62% of the total explained variation amongst the tested genotypes. The selected cowpea genotypes for most of agronomic characteristics are useful and candidate genetic resources for the development of breeding population in cowpea breeding and enhanced production and productivity for food and nutrition in the country.     

Ontogenetic-based sequential path analysis of grain yield and its related traits in several winter wheat cultivars

Studies that provide representative insights for determining yield through its related traits during the ontogeny of modern cultivars subjected to sources of environmental variation are limited for different crops, including wheat. Most of the empirical evidence on the relationships between the yield of small grain cereal crops and its contributing traits has been obtained under dry or semidry conditions. The aims of this paper were to (1) illustrate how an path analysis can be used to clarify and interpret the relationships between grain yield (GY), yield components, and other yield-related traits of 25 winter wheat cultivars subjected to sources of environmental variation and (2) determine how the yield-related traits contribute to the yield variation. The data used in this analysis were generated from multi-environment trials across wheat-growing areas in Poland. Using Ward’s clustering procedure was capable of identifying the most critical predictor traits of the yield components and their contributions to cultivar-focused GY variation. Our findings document, confirm, and improve the basic biological understanding of how to grow modern wheat cultivars for high GY through effectively stimulating the improvement of yield-related traits through the optimization of developmental stage-based agronomic strategies. Our results confirmed empirically that modern European wheat cultivars grown in a temperate climate require favorable conditions, the use of appropriate N fertilizer and growth regulators, and the application of fungicide to protect against leaf diseases and to provide conditions that effectively increase the time to anthesis, the Leaf Area Index per spike at anthesis, and the grain filling duration, and reduce plant height and flag leaf disease severity, thus leading to a high GY. A high yield level is obtained by the performance of preferred yield-related traits that can maintain the three yield components at relatively high levels.     

The variation of phosphorous content,grain yield,and rhizosphere microbial biomass among durum wheat cultivars under salinity stress

ABSTRACT

The effectiveness of plant–soil synergies is largely modulated by interaction between cultivar and rhizosphere microbiome. We evaluated the agronomic performance of six durum wheat cultivars, in two semi-arid locations in Tunisia that differed in their irrigation water salinity: S1 (6 dS m^?1) and S2 (12 dS m^?1). The two-consecutive-year field experiments assessed the effects of the microbial biomass carbon (MBC), leaf phosphorus (LP) and rhizosphere phosphorus (P) on the grain yield (GY) and yield components at tillering and flowering stages. Overall, in saline conditions, cultivars differed in above- and below-ground traits, particularly, with tolerant cultivars presenting relatively greater MBC, P and LP. Furthermore, in S2, GY positively correlated with MBC (r = 0.69), LP (r = 0.80) and P (r = 0.79). Additionally, in S2, MBC positively correlated with P (r = 0.87) and LP (r = 0.85) at flowering. This result was further confirmed by multiple linear regression (step-wise) analysis, which revealed that MBC and LP were the determinant components of GY variability under S2. The present study demonstrates that LP and soil P are mandatory for improving the management of durum wheat. Salinity tolerance was largely affected by the cultivars’ rhizosphere MBC.     

Reduced trigonelline accumulation due to rhizobial activity improves grain yield in peanut (Arachis hypogaea L.)

Abstract

Crop improvement for drought tolerance is critical for the future of crop production. The objectives were to examine the relationship between trigonelline (TRG) accumulation and yield traits in 10 peanut (Arachis hypogaea L.) genotypes inoculated with two commonly used nitrogen-fixing Rhizobium spp., and to evaluate a role of TRG on growth traits. TRG increased as a defensive metabolite in response to water deficit, but resulted in the reduction of the number of nodules and yield. Symbiotic rhizobial activity helped plants to improve yield particularly in a fully irrigated field rather than under reduced irrigation. TRG concentrations in genotypes (7 out of 10) increased under reduced irrigation as compared with those under full irrigation in two years. Mean number of nodules at maturity (120 days after planting) across genotypes under reduced irrigation were 89 in the control, 111 in Lift, and 161 in Histick treatments, among which Histick was significant (p < 0.05) for nodulation. Mean pod yields in the control, Histick, and Lift treatments were 1.69, 2.34 and 1.87 Mg ha^-1, respectively, under reduced irrigation. Under full irrigation, pod yields were 3.35 in the control, 4.50 in Histick and 3.41 Mg ha^-1 in Lift treatments, but were more significantly improved as treated with Histick than other treatments. Genotype ICGS-76 produced the highest pod yield (5.13 Mg ha^-1) as treated with Histick. All genotypes treated with Histick and Lift biosynthesized less TRG (decreased from 5.8 to 65.3% relative to the control) but produced larger numbers of pods (increased from 9.2 to 80.4% relative to the control), which resulted in substantially higher pod yields.     

Association of Barley Kernel Hardness with Physical Grain Traits and Food Processing Parameters

Kernel hardness is not a well‐characterized food quality trait in barley. Unlike wheat, not much is known about the effect of barley kernel hardness on food processing. Ten barley genotypes differing in single kernel characterization system hardness index (SKCS‐HI) (30.1–91.2) of dehulled kernels were used to determine the association of barley HI with other physical grain traits and food processing parameters. Thousand kernel weight (TKW) values of 10 genotypes were 29.7–38.1 g. Values for bulk density of grains were 721.1–758.9 kg/m³. Crease width and depth values were 0.9–1.3 mm and 0.4–0.7 mm, respectively. Barley HI showed no significant association with TKW, bulk density, or kernel crease dimensions. Kernel loss due to pearling after 325 sec of abrasion was 28.8–38.4% and showed significant negative correlation with HI (r = –0.87, P < 0.01). Proportion of barley flour particles >106 μm had values of 34.5–42.0%, and starch damage values were 1.8–4.5% among those 10 barley genotypes. HI showed significant positive correlations with both proportion of barley flour particles >106 μm (r = 0.93, P < 0.01) and starch damage (r = 0.93, P < 0.01). Water imbibition of barley kernels and cooked kernel hardness did not show significant correlation with HI.     

Agro-morphological characterisation and selection of sorghum landraces

Sorghum [Sorghum bicolor (L.) Moench] grown under rain-fed conditions is frequently affected by drought stress at different stages, resulting in reduced grain and biomass yield. The aim of this study was to characterise sorghum landraces and to select farmer-preferred medium-maturing genotypes under rainfed and irrigated conditions. Hundred and ninety-six sorghum accessions were evaluated at Kobo site of the Sirinka Agricultural Research Center in 2014/2015 in Ethiopia. Data collected from 14 traits were subjected to analysis of variance, cluster analysis, Pearson’s correlation coefficient analysis, path coefficient analysis and principal component analysis (PCA). Significant genotypic differences (p?<?0.05) were observed. Medium-maturing and drought tolerant sorghum genotypes including E-72457, E-72438, E-72435, E-206214, E-72449, E-75460 and E-75458 with superior agronomic performance were recommend for large-scale production or for further breeding. The genotypes evaluated under rain-fed and irrigated conditions were grouped into five and six clusters, respectively, representing varied different heterotic groups. Grain yield had significant and positive correlation with yield-related traits assessed under the two test conditions. Further, path coefficient analysis revealed that days to maturity under rainfed condition and harvest index under irrigated condition had the highest positive direct effects on grain yield, therefore can be targets for direct selection. Overall, there was marked genetic diversity among the tested genotypes. Suitable medium-maturing farmers-preferred accessions selected from the study will be useful for effective breeding for drought tolerance and medium-maturity.     

Agronomical,quality, and molecular characterization of twenty Italian emmer wheat (<Emphasis Type="Italic">Triticum dicoccon</Emphasis>) accessions

Emmer wheat (Triticum dicoccon Schrank, 2n = 4x = 28) consists in a hulled wheat; its cultivation has been drastically reduced during the last century as a consequence of its low yield. Recently, its agronomic and nutritive values, as well as the increase of popularity of organic agriculture, have led to a renewed interest making its cultivation economically viable in the marginal lands with an increase of the cultivated areas. In Italy, it mainly survives in few marginal lands of central and southern Italy, where local varieties, adapted to the natural environment from where they originate, are used; moreover, some selected lines have also been developed. In the present work, agro-morphological and qualitative traits, together with molecular analyses of 20 emmer accessions consisting of Italian landraces, breeding lines, and cultivars, were performed. The field experiments were conducted for two consecutive years (2001/2002–2002/2003) in two locations: Viterbo in central Italy, and Foggia in south Italy. The analyzed emmer wheat accessions showed a good amount of genetic variability for both evaluated agro-morphological and molecular traits. This study illustrates an increase in earliness, GY, TW, TKW, and YI going from landraces, breeding lines to cultivars, while the variability does not change proportionally.     

Genetic properties of drought tolerance indices in sunflower

Abstract

The objective of the present study was genetic analysis of yield-based drought tolerance indices using the diallel method. Twenty-one genotypes of sunflower (Helianthus annuus L.) derived from a half diallel cross between six inbred lines were evaluated in both stress and non-stress conditions using a randomized complete block design for each one. Eight drought tolerance indices comprising stress tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HM), stress susceptibility index (SSI), tolerance index (TOL), yield index (YI) and yield stability index (YSI) were calculated based on grain yield under stress and non-stress environments. Significant genotypic differences were observed in TOL, GMP, MPSTI, HM and YI. Diallel analyses revealed the importance of both additive and non-additive gene effects in GMP, STI, HM and YI. However, the Baker ratio supported the predominance of an additive effect in their expression. Our results demonstrated that SSI, YSI, TOL and MP are not reliable indices to select drought tolerant genotypes in sunflower breeding programmes because of their low heritability. Indices such as GMP, STI, HM and YI were moderately heritable and are usually able to select high-yielding genotypes in both environments and could be usefully employed in drought tolerance breeding programmes of sunflower.     

早熟区不同播期旱地玉米产量对施肥水平和种植密度的响应

为明确早熟区不同播期旱地玉米产量对施肥水平和种植密度的响应特征及趋势, 完善高产高效密植栽培技术, 采用田间试验法, 以传统耕种方式为对照, 于2010-2011年连续2年研究了不同播期[秋耕早播和正常播种(对照)]、施肥水平和种植密度对旱地玉米主要产量性状的影响。结果显示, 2010年(遭遇"卡脖旱")秋耕早播经济产量、收获指数和水分利用效率分别较对照增加9.0%、7.1%和6.4%(P<0.01), 百粒重(P<0.01)和出籽率(P<0.05)显著大于对照。2011年(丰水年)增幅明显增加, 经济产量、收获指数和水分利用效率分别较对照增加13.1%、8.8%和8.5%(P<0.01), 穗粒数(P<0.05)和百粒重(P<0.01)显著大于对照。随着施氮水平增加, 经济产量和生物产量都呈增加趋势, 但2010年秋耕早播过量施肥造成明显减产, 2011年施肥处理经济产量显著大于不施肥处理, 而不同施氮水平间无显著差异。秋耕早播较低的施肥量可获得较高的产量。随着密度增加, 2010年玉米经济产量和生物产量呈二次抛物线型, 秋耕早播获得最高经济产量的种植密度为7.5万株·hm^-2, 该年型秋耕早播可通过适当增密获得高产, 而对照增密会造成严重减产。2011年经济产量和生物产量随种植密度增加而增加, 但当密度增加到7.5万株·hm^-2时经济产量不再显著增加。受旱年份秋耕早播较对照缩小了密度效应, 为增产奠定了一定基础, 且施肥和密度对产量存在显著互作效应, 而丰水年互作效应不明显。对照该生态区目前的玉米栽培措施, 在适期早播的基础上, 减少肥料用量和适当增密是该区实现玉米高产高效栽培的技术方向。     

Responses of wheat yield,quality and bread-making properties on the sulphur fertilization

This study presents a versatile influence of sulphur (S) application on winter wheat – beginning with the influence on the grain yield and primary quality indices, followed by the one on the bread-making properties of flour and dough, and ending with the one on the quality indices of baked products. Field experiments were conducted at two locations on haplic Luvisol and calcaric Cambisol during five years. S was given as NS-fertilizers on the background of N100 during wheat tillering. Flour and dough properties for bread-making were determined by using a farinograph Brabender. The baking tests were carried out in laboratory conditions. The influence of S on the grain yield and quality, and bread-making properties of wheat depended on the year and location. As the average of field experiments conducted at two locations, the application of S significantly increased the grain yield (r?=?0.960). The increasing yields were accompanied by decreasing contents of wet gluten (r?=?0.825). However, the significant positive (r?=?0.938) effect of the S application on the Gluten index was revealed, which is a good predictor of the baking quality of wheat flour. The S addition by nitrogen fertilization resulted also in a positive shift of the N:S ratio in grains, which is better for the bread-making quality. The significant positive effects of the S application on the dough stability time (r?=?0.898) and on the farinograph quality number (r?=?0.917) were demonstrated. The loaf volume was significantly (r?=?0.842) increasing under the influence of S. Thus, the application of S in parallel with increasing yields improved several bread-making parameters of wheat.     

Relationships among important traits in the nitrogen economy of winter wheat

Identification and utilization of important attributes in the nitrogen economy of wheat (Triticum aestivum L.) should provide a basis for increasing grain protein percentage (GPP). The objectives of this study were to determine the magnitude of genetic variability of some factors important in the nitrogen economy of wheat, their relationship to one another, and their influence on grain yield (GY) and GPP. Twenty‐five hard red winter wheat genotypes representing a wide range of GY, GPP, and plant stature were grown in field trials over a 2‐year period. Significant differences were found for harvest index (HI) and nitrogen harvest index (NHI). Total nitrogen at anthesis (TNA), total nitrogen at maturity (TNM), and biological yield (BY) did not differ significantly. GPP was positively correlated with TNM and BY and negatively correlated with TNA, HI, and GY. GPP was not correlated with NHI, however, stepwise regression of GPP and grain protein yield revealed NHI as a common component, with a positive coefficient. In addition, NHI was positively correlated with GY. Selection of parents with complementary traits for nitrogen‐use efficiency may allow for simultaneous increases in GY and GPP.     

MAIZE RESPONSE TO YIELD AND YIELD TRAITS WITH DIFFERENT NITROGEN AND DENSITY UNDER CLIMATE VARIABILITY

To study yield and yield traits of maize, two experiments were conducted in 2006 as spring and summer crops and repeated in 2007. Three plant populations (43, 53, and 67 thousands ha^-1) and three nitrogen (N) rates (90, 120 and 150 kg N ha^-1) were compared in a completely randomized block design with split plot arrangement. The treatments plant population was assigned to the main and N to sub plots in three replications. Sowing of spring crop was done in March and harvested in July and likewise the summer crop in July and harvested in November. Each experimental unit comprised of 5 × 6 m area having eight rows spaced 0.75 m. Experimental results revealed that grain yield (GY) of summer was higher than spring season. Higher GY was associated with increases in the plant population and nitrogen rate. The treatment plant population of 53,000 and 67,000 ha^-1 did not differ. However, each increase in the N rate significantly increased GY. This increase in the GY by increasing N was due to increases in the ear length (EL), ear diameter (ED), grain number (GN) and thousand grain weight (TGW). Increasing plant population of maize did not show any remarkable changes in the yield traits. The study revealed that differences in GY due to seasonal climate cannot be rewarded with increase in either plant population or nitrogen rates. Moreover, spring and summer season maize crops can economically be planted with 150 and 120 kg N ha^?1 at 53,000 and 67,000 ha^?1 populations, respectively, to save environment and production cost.     

Phenotypic tendency of achene yield and oil contents in sunflower hybrids

ABSTRACT

The knowledge about heterosis breeding of achene yield in sunflower is known; however, dissection of the genetic components of achene yield and seed quality traits is limited. Therefore, the prescribe study was conducted using Line × Tester design to determine combining abilities, and about the maternal-and-paternal gene actions involved in achene yield and seed quality traits in 21 single cross hybrids. Significant mean differences for achene yield and seed quality traits were observed, with total attributed variation (R^2?=^?0.89). Principal component analysis (P?<?0.05) explained 92.6% variation and using factor analysis, we found factor 1 had primary variables (AW, AL, AT, HD, PH, PC, LA and OC) contributed 35.6% variation to achene yield. Combining ability analysis showed the positive general combining ability for E%, HD, PH, 100 AW and AYP in parental inbred lines, whilst, hybrids had positive specific combining ability for E%, HD, PH, 100 AW, DTF, DTM, OA, LA, OC and AYP. Females contributed significantly higher (P?<?0.05) for AYP, E%, HD, NWPH, PH, 100 AW, LA and OA than that of males. Two-way hierarchical clustering showed the most promising hybrid H₅ (A-18?×?G-79) in Cluster V. The hybrid H₅ also showed heterosis, heterobeltosis and commercial heterosis, therefore, genetic exploitation of H₅ is highly desirable in future breeding to map QTLs/genes in arid/semi-arid zones and /or similar growing conditions to boost up yield and seed quality traits.     

Response of photosynthetic active radiation interception,dry matter accumulation,and grain yield to tillage in two winter wheat genotypes

ABSTRACT

To examine the effects of winter wheat genotypes on dry matter (DM) accumulation and grain yield (GY) under no-tillage conditions in North China Plain (NCP), a field experiment was conducted using the genotypes Tainong 18 (F) and Jimai 22 (J). Two tillage systems were tested, conventional tillage (CT) and no-tillage (NT) during the 2015/2016 and 2016/2017 winter wheat growing seasons. Genotypes and tillage systems were compared regarding DM accumulation, GY, leaf area index (LAI), photosynthetic active radiation (PAR) interception, and flag leaf fluorescence parameters. LAI, PAR interceptions, and flag leaf fluorescence parameters were significantly higher under CT than under NT conditions. This suggests that the efficiency of light harvesting by the PSII reaction center of leaves can increase due to CT. DM accumulation was significantly higher under CT than under NT. Spike DM accumulation was higher in F than in J in the heading and the filling stages. In both growing seasons, GY was significantly higher under CT than under NT, GY of NTF was significantly higher than that of NTJ, which was due to a significantly higher number of kernels per spike. This indicates that genotype F can compensate for a low GY due to NT.     

Genetic relationship among selected heat and drought tolerant bread wheat genotypes using SSR markers,agronomic traits and grain protein content

ABSTRACT

Assessing the genetic variation and relationships present in crop germplasm is a pre-requisite for parental selection and breeding. The objective of this study was to determine the genetic relationships present among selected heat and drought tolerant wheat genotypes using simple sequence repeat (SSR) markers, agronomic traits and grain quality parameters to select desirable parents for breeding. Twenty-four agronomically selected wheat genotypes sourced from the International Maize and Wheat Improvement Centre (CIMMYT)’s heat and drought tolerance nursery and four local check varieties were genotyped using 12 selected polymorphic SSR markers. The test genotypes were phenotyped using yield and yield-component traits, and grain protein content (GPC) under non-stressed (NS) and drought-stressed (DS) conditions. Expected heterozygosity mean value of 0.58 indicated moderate genetic diversity for breeding. The studied wheat genotypes were delineated into six genetic groups using cluster analysis. Significant genotypic differences were observed for agronomic traits and GPC under NS and DS conditions. Genetically unrelated breeding parents including LM02, LM13, LM23, LM41, LM44, LM71, LM73 and LM75 were selected for population development and breeding for enhanced grain yield and protein content under heat and drought-stressed environments.