Geometric Mean Productivity Research Articles

Screening of drought tolerance indices for selection of resistance wheat (Triticum aestivum L.) landraces under drought stress conditions

Abstract During the cropping season 2016-2017, an experiment was conducted in a split plot design to study the response of 25 wheat genotypes to drought stress under irrigated and minimal irrigation conditions. Different drought tolerance indices for 25 bread wheat (Triticum aestivum L.) genotypes were evaluated. The calculation drought tolerance indices was based on the grain yield of wheat under irrigated and water stress conditions. The result indicated a significant effect of drought stress on the yield of different wheat genotypes based on mean values of different drought tolerance indices. Among the studied different indices, mean productivity (MP), stress tolerance index (STI), and geometric mean productivity (GMP) were more efficient to discriminate between drought sensitive and drought tolerant genotypes based on the calculation of correlation coefficient and multivariate analysis. Twenty-five genotypes were classified into tolerant and susceptible groups through drought tolerance indices using cluster analysis. Among the genotypes, C-306, WH 1236, WH 1235, and GW 477 having higher yields under drought conditions which showing their stability under stress conditions. The most yield stable genotypes under adverse environment were identified by multivariate analysis of drought tolerance indices individually or in combination. From the result, we concluded that GMP, MP and STI are more efficient drought tolerance indices among other indices to identify stable genotypes under stress conditions.

Exploring the usefulness of drought tolerance indices in screening of maize inter-racial derivatives

Abstract Among all the abiotic factors affecting maize yield, drought stress is the most destructive one. Since drought tolerance is a complicated trait that is difficult to quantify, screening for stress involves measuring the effects of stress on several traits, most notably plant yield. Selection using the drought tolerance indices is an easy way to identify the stable and tolerant genotypes based on yield performances alone. The current study aims to identify suitable maize hybrids with high drought tolerance. A total of 30 maize-teosinte hybrids and 3 checks were raised under optimal and water-stressed environments and were screened using twelve different drought tolerance indices. It was observed that the inter-racial hybrids viz., G24, G27, and G29 were better than the drought tolerant Zea mays ssp. mays check C3 for yield and most of the indices. The indices STI, TOL, GMP, MP, YI, DI, SSPI, K1STI, and K2STI were observed to be significantly correlated with yield under stress and optimal environments. Based on the yield both environments, the genotypes were classified under four groups, with Group A consisting of genotypes with high yields under both environments. The indices Stress Tolerance Index (STI), Geometric Mean Productivity (GMP), Yield Index (YI), and Modified Stress Tolerance Index (K2STI)were identified for their ability to discriminate Group A from the other genotypes and these indices could be utilized to screen for drought tolerance with high yield.Component Analysis revealed two principal components contributing up to 98.15 percent of the cumulative variation. The PCA biplot identified the hybrids viz., G24, G27, G14, G19, and G25 as tolerant ones. Based on the index scores, the hybrids viz., G27, G29, G17, G20,and G24were identified as the top-ranking genotypes, with high and more stable yields under both stress and optimal environments. Keywords: Drought index, maize, 3D plot, inter-racial hybrids, teosinte

Genome-wide association mapping and genomic prediction of water deficit stress tolerance indices in spring bread wheat

Genome-wide association mapping (GWAM) is crucial for identifying the genetic architecture of quantitative traits, such as drought tolerance indices in bread wheat. This study aims to identify Marker-Trait Associations (MTAs) and genes related to drought tolerance indices in wheat. Seven drought tolerance indices were calculated based on grain weight per spike under field drought stress (FDS) and field non-stress (FNS) conditions. These indices included mean productivity (MP), geometric mean productivity (GMP), relative drought index (RDI), stress tolerance index (STI), tolerance index (TOL), stress susceptibility index (SSI), and yield stability index (YSI). Genotyping of the samples was performed using single nucleotide polymorphism (SNP) markers. A total of 96 MTAs were identified for the studied indices and conditions FNS and FDS in this experiment, with a threshold of -log10p ≥ 3.0. These included FNS, FDS, GMP, MP, STI, SSI, RDI, and YSI, with 15, 11, 16, 16, 20, 6, 6, and 6 MTAs, respectively. The MTAs identified for the drought tolerance indices GMP, MP, and STI were located on chromosomes 2 A, 3B, and 6 A, respectively. Moreover, this study identified four genes related to the indices, namely “TraesCS2B02G000100,” “TraesCS3A02G000100,” “TraesCS2B02G000200,” and “TraesCS4B02G000100”. These genes play a crucial role in drought tolerance and can be utilized for marker-assisted selection to enhance drought tolerance wheat genotypes.

Multi-locus genome-wide association study for grain yield and drought tolerance indices in sorghum accessions.

Drought is a significant factor that causes yield loss in essential cereal crops such as sorghum [Sorghum bicolor (L.) Moench], necessitating the development of drought-tolerant varieties adaptable to various water conditions. This study aimed to pinpoint drought-tolerant sorghum lines and genomic regions for tolerance by utilizing 216 sorghum accessions in stressed and non-stressed environments at two locations. Genetic diversity was evident among accessions in terms of grain yield under different watering regimes. Drought stress indices such as the stress tolerance index, mean productivity, geometric mean productivity, harmonic mean productivity, yield stability index, and yield index were identified as effective measures for selecting drought-tolerant sorghum. Cluster analysis classified genotypes into four groups based on their association with grain yield, highlighting Acc. #28546 and Acc. #216739 as highly drought tolerant across environments. This study identified 32 and 22 quantitative trait nucleotides (QTNs) for drought indices and grain yield under stress and non-stress conditions, respectively, at two locations, with five common QTNs linked to multiple drought indices. Colocation analysis revealed that these QTNs were associated with known stay-green-related quantitative trait loci (QTLs), and 47 putative genes near these QTNs potentially influenced drought tolerance traits. It is suggested that accession selection considers multiple indices for robust evaluation. Understanding the identified genes and their functions provides insights into the genetic mechanisms governing plant responses to drought stress, offering prospects for developing improved drought-resistant sorghum varieties through further genetic research.

Evaluation of barley genotypes for drought adaptability: based on stress indices and comprehensive evaluation as criteria.

The prevalence of drought events worldwide emphasizes the importance of screening and cultivating drought-adapted crops. In this study, 206 germplasm resources were used as materials, dry weight as target trait, and two genotyping methods as criteria to evaluate drought adaptability at the seedling establishment stage. The results showed a significant decrease in average dry weight of the tested germplasm resources (from 746.90 mg to 285.40 mg) and rich variation in the responses of dry weight among each genotype to drought (CV=61.14%). In traditional evaluation method, drought resistance coefficient (DC), geometric mean productivity index (GMP), mean productivity index (MP), stress susceptibility index (SSI), stress tolerance index (STI), and tolerance index (TOL) also exhibited diversity in tested genotypes (CV>30%). However, these indices showed varying degrees of explanation for dry weight under stress and non-stress environments and failed to differentiate drought adaptability among genotypes clearly. In new evaluation method, four stress indices were developed to quantify barley seedling production and stability capacities. Compared to traditional stress indices, the stress production index (SI) explained dry weight more comprehensively under stress conditions (R2 = 0.98), while the ideal production index (II) explained dry weight better under non-stress conditions (R2 = 0.89). Furthermore, the potential index (PI) and elasticity index (EI) eliminated disparities in traditional stress indices and comprehensively clarified the contribution of elasticity and potential to production capacity under drought stress. Ultimately, through grading evaluation and cluster analysis, the tested germplasm resources were effectively categorized, and 11 genotypes were identified as suitable for cultivation in arid areas. Overall, the comprehensive evaluation method based on the newly developed stress indices surpasses the traditional method in screening drought adaptability of crops and serves as a vital tool for identifying high-stability and high-production capacities genotypes in various environments, which is expected to provide practical guidance for barley planting and breeding in arid areas.

Morpho-physiological characterization and selection of heat tolerant wheat lines using selection indices

Heat stress is one of the major constraints in wheat production due to its adverse effect on grain yield and component traits. Moreover, it negatively affects the physiological, biochemical and quality traits of wheat. Therefore, selection of heat tolerant wheat lines is one of the major breeding goals for wheat scientist. In present study, 238 recombinant inbred lines were evaluated along with their parents WH 711 × WH 542 under timely and late sown (heat stress) condition. The heat tolerance indices were calculated based on grain yield under normal and stress conditions. The mean grain yield of 238 wheat lines was reduced by 20.54% suggesting critical effect of heat stress on grain yield. The harmonic mean (HM), stress tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP), and mean relative performance (MRP) were correlated significantly and positively with grain yield under stress and normal conditions. Whereas, Tolerance index (TOL) was correlated negatively with grain yield under stress conditions and positively under normal condition. Based on STI, MP, HM, GMP and MRP, wheat lines WL 92, WL 119, WL 114, WL 110, WL 6 were identified as heat tolerant and could be utilized as potential lines for increasing heat stress tolerance of future wheat breeding programs.

Morpho-physiological and yield traits for selection of drought tolerant Urochloa grass ecotypes.

Drought has become more recurrent and causes a substantial decline in forage yields leading to strain on feed resources for livestock production. This has intensified the search for drought-tolerant forages to promote sustainable livestock production. The objective of this study was to identify drought-tolerant Urochloa grasses and to discern their morpho-physiological and yield traits to water stress as well as the relationship between these traits and indices of drought resistance. The results showed that the ecotypes, water regimes and their interaction significantly influenced all the studied morpho-physiological and yield traits. There was a significant decrease in plant height, number of leaves and tillers, dry matter yield, relative water content, photosystem II and efficiency of photosystem II with an increase in non-photochemical quenching. The principal component analysis revealed that the performance of Urochloa grass ecotypes was different under water sufficient (WS) and water deficit conditions. Drought tolerance indicators (mean productivity, geometric mean productivity, tolerance index and stress tolerance index) were most effective in identifying Urochloa ecotypes with high biomass production under both water deficient and WS conditions. Ecotypes K17, K7, Kisii, Busia and Kakamega were the most drought tolerant, Basilisk, K6, K10, K19 and Toledo were moderately tolerant whereas, CIAT6385, CIAT16449, K13, K5 and K9 were drought sensitive. The five drought-tolerant Urochloa ecotypes should be tested for sustainable biomass production under field conditions and used in breeding programmes to develop high-yielding drought-tolerant varieties.

Hydroponic Screening at Early Seedling Stage Identified Sources of Salinity Tolerance in Wheat (Triticum aestivum L.) Crop

Wheat is a vital crop globally, essential for agriculture, economics, and food security. However, in arid and semi-arid conditions, wheat production faces significant challenges due to low water availability, uneven rainfall distribution, and high soil salinity. The germination and early seedling stages are particularly vulnerable to these stresses. Therefore, this study assessed 15 wheat genotypes for their tolerance to salinity stress during early growth stages, using a hydroponic system with four salt stress levels (0, 50, 100, and 150 mM NaCl). Significant differences were observed for genotype and salinity main effects and their interaction on all investigated traits, indicating considerable variability in the response to salt stress among the investigated wheat cultivars. High NaCl concentrations led to substantial reductions in measured parameters across genotypes, with some showing resilience while others exhibited heightened sensitivity. Stress tolerance indices, such as mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HM), stress tolerance index (STI) and yield index (YI), were identified as reliable indicators for selecting salt-tolerant wheat cultivars. Consequently, Sidi Okba (G11), Ziad (G12), Tamezghida (G13) and Zidane (G14) emerged as the most promising, displaying acceptable performance under both non-stress and salt-stress conditions. These genotypes could serve as valuable genetic resources for breeding programs aimed at enhancing wheat’s salinity tolerance, particularly in arid and semi-arid regions.

Evaluation of yield-based selection indices for drought tolerance involving recombinant inbred line population derived from a chickpea cultivar (C. arietinum L.) and its wild relative (C. reticulatum)

AbstractDrought is a major abiotic stress worldwide limiting chickpea yield drastically. Low heritability and high genotype × environment interactions make the trait-based breeding strategy an unreliable approach. This study was planned to identify the drought-tolerant lines by evaluating yield-based selection indices in a recombinant inbred line (RIL) population derived from an inter-specific cross between drought-tolerant genotype GPF 2 (Cicer arietinum L.) and drought-sensitive accession ILWC 292 (C. reticulatum) at two locations in India (Ludhiana and Faridkot). A total of six yield-based selection indices were calculated and significant variation was observed in the RILs and their parents for yield-based selection indices at both locations. A holistic approach across association analysis and principal component analysis identified drought tolerance index, mean productivity, geometric mean productivity and harmonic mean productivity as key selection indices, which could be used for indirect selection of drought-tolerant lines. Overall, on the basis of these approaches, a total of 15 promising RILs were identified for their use in chickpea breeding programme for developing drought-tolerant cultivars.

Selection of M5 mutant lines of wheat (Triticum aestivum L.) for agronomic traits and biomass allocation under drought stress and non-stressed conditions.

In the face of climate changes and limited water availability for irrigated crop production, enhanced drought tolerance and adaptation is vital to improve wheat productivity. The objective of this study was to determine the responses of newly bred and advanced mutant lines of wheat based on agronomic traits and biomass allocation under drought-stressed and non-stressed environments for production and breeding. Fifty-three mutant lines, including the parental check and six check varieties, were evaluated under non-stressed (NS) and drought stressed (DS) conditions in the field and controlled environments using a 20 x 3 alpha lattice design with two replicates. The following agronomic data were collected: days to 50% heading (DTH), days to maturity (DTM), plant height (PH), number of productive tillers (PTN), shoot biomass (SB), root biomass (RB), total biomass (TB), root: shoot ratio (RSR), spike length (SL), thousand seeds weight (TSW) and grain yield (GY). Data were analyzed and summarized using various statistical procedures and drought tolerance indices were computed based on grain yield under NS and DS conditions. Significant (P < 0.05) differences were recorded among the mutant lines for most assessed traits under NS and DS conditions. Grain yield positively and significantly (p < 0.001) correlated with PTN (r = 0.85), RB (r = 0.75), SB (r = 0.80), SL (r =0.73), TB (r = 0.65), and TSW (r = 0.67) under DS condition. Principal component analysis revealed three components contributing to 78.55% and 77.21% of the total variability for the assessed agronomic traits under DS and NS conditions, respectively. The following traits: GY, RB, SB, and PTN explained most of the variation with high loading scores under DS condition. Geometric mean productivity (GMP), mean productivity (MP), harmonic mean (HM), and stress tolerance index (STI) were identified as the best drought tolerance indices for the identification of tolerant lines with positive correlations with GY under NS and DS conditions. Among the advanced lines tested, LMA16, LMA37, LMA47, LMA2, and LMA42 were selected as the superior lines with high performance and drought tolerance. The selected lines are recommended for multi-environment trails and release for production in water-limited environments in South Africa.

Genetic variability and evaluation of water-deficit stress tolerant of spring bread wheat genotypes using drought tolerance indices

Water deficit stress is one of the most important environmental factors that reduce grain yield in bread wheat. Despite the recent progress in breeding this plant, there is still a need to improve bread wheat cultivars that tolerate water stress in the country. In the current research, 100 genotypes of spring bread wheat during the years 2020–2021 and 2021–2022 in two conditions of non-stress and water deficit stress in the form of a simple 10x10 lattice square design at the beginning of flowering in Gachsaran Research Center located in the south of Iran. Eight quantitative indices of tolerance to water deficit were calculated. Principal component analysis (PCA), hierarchical cluster analysis (HCA), analysis of variance, and Pearson correlation were carried out in this study. According to the data, significant genotypic variation was seen among genotypes for both individual yield and drought indices. Geometric Mean Productivity (GMP) recorded the lowest coefficient of variation (CV) value with 10.6 %, while Tolerance Index (TOL) recorded the highest CV value with 45.4 %. The heritability of several of the indices is moderate to high; the Stress Susceptibility Index (SSI) has the greatest heritability at 0.96. Four distinct clusters were formed from the 100 genotypes. PC1 and PC2 make up 98.4 % of the total variance. Specifically, PC1 covers 68.9 %, while PC2 accounts for the remaining 29.5 %. These chosen genotypes will act as parent plants in breeding initiatives to create novel varieties resistant to drought.

Multi-trait selection for agronomic performance and drought tolerance among durum wheat genotypes evaluated under rainfed and irrigated environments

Summary Durum wheat (Triticum turgidum L. subsp. durum) is a major crop in the Mediterranean region, widely grown for its nutritional value and economic importance. Durum wheat breeding can contribute to global food security through the introduction of new cultivars exhibiting drought tolerance and higher yield potential in the Mediterranean environments. In this study, 25 durum wheat genotypes (23 elite breeding lines and two national checks) were evaluated for five drought-adaptive traits (days to heading, days to maturity, plant height, 1000-kernel weight and grain yield) and eight drought tolerance indices including stress tolerance index (STI), geometric mean productivity (GMP), mean productivity (MP), stress susceptibility index, tolerance index, yield index, yield stability index and drought response index under rainfed and irrigated conditions during three cropping seasons (2019–2022). Multi-trait stability index (MTSI) technique was applied to select genotypes with higher grain yield, 1000-kernel weight, plant stature and early flowering and maturity simultaneously; as well as for higher drought tolerance in each and across years. A heat map correlation analysis and principal component analysis were applied to study the relationships among drought tolerance indices and the pattern of variation among genotypes studied. Factor analysis was applied for identification of traits that contributed most in stability analyses. Significant and positive correlations were observed among the three drought tolerance indices of STI, GMP and MP with mean yields under both rainfed and irrigated conditions in each and across years, suggest the efficiency of these indices as selection criteria for improved drought tolerance and yield performance in durum wheat. The genotypes ranked based on MTSI varied from environment to environment, showing the impact of environment on genotypes performance, but several of the best performing lines were common across environments. According to MTSI for agronomic traits, the breeding lines G20, G6, G25 and G18 exhibited highest performance and trait stability across environmental conditions, and the selected genotypes had strength towards grain yield, 1000-kernel weight and earliness. Using the MTSI, breeding lines G20, G5, G16 and G7 were selected as drought tolerant genotypes with high mean performance. Breeding line G20 from ICARDA germplasm showed highest trait stability performance and drought tolerance across environments. The MTSI was a useful tool for selecting genotypes based on their agronomic performance and drought tolerance that could be exploited for identification and selection of elite genotypes with desired multi-traits. Based on the results, breeding lines G20 and G6 should be recommended for short-term release programme and/ or utilized in durum wheat population improvement programme for agronomic performance and drought tolerance traits that tolerate climate variations.

Heat tolerance indices as tools for characterizing resilient wheat (&lt;i&gt;Triticum aestivum&lt;/i&gt;) RILs population under thermal stress

The escalating impact of heat stress on agriculture due to climate change has necessitated the development of heat- tolerant crop varieties. To address this, a study was carried out at research farm of CCS Haryana Agricultural University, Hisar, Haryana during winter (rabi) seasons of 2018–19 and 2019–20 under two different environments (normal and late sown). Evaluation of multiple stress indices and their relationship with grain yield per plot was done using 200 recombinant inbred lines (RILs) of wheat (Triticum aestivum L.). Positive correlation was observed between grain yield and stress tolerance index, mean productivity, geometric mean productivity, harmonic mean and mean relative performance, while negative correlations existed with heat susceptibility index, tolerance, stress susceptibility index and reduction under stress conditions. Stepwise regression analysis revealed the importance of mean productivity, yield index, geometric mean productivity, stress tolerance index, and reduction in predicting grain yield. Principal Component Analysis highlighted the significance of tolerance and reduction in explaining the variance, with PC-1 labeled as the resilience and stress tolerance component and PC-2 as the yield stability and performance component. These findings were able to select 13 most heat tolerant RILs, performing better than national level check genotype WH730 and emphasized the role of stress indices especially HSI and TOL in characterizing genotypic responses to heat stress and guiding the selection of heat-tolerant genotypes for sustainable crop improvement. In the context of heat stress tolerance, understanding and harnessing transgressive segregants could lead to the development of crop varieties that not only tolerate, but thrive in challenging environments, ensuring sustainable food production under changing climatic conditions.

Yield evaluation and identification of drought tolerant lines based on stress tolerant indices, ranking method and multivariate analysis in sweet potato (Ipomoea batatas Lam)

Sweet potato is a vital food crop in tropical and sub-tropical regions, but its sustainable production is hampered by drought stress. This study was conducted at ICAR-CTCRI, Regional Centre, aimed to evaluate 27 sweet potato genotypes to identify lines with drought tolerance. The experiment employed a split-plot design with a randomized complete block arrangement under both irrigated and drought stress conditions over two years, during Sep-2017 to Jan-2018 and Sep-2018 to Jan-2019. The results of the combined analysis of variance revealed significant differences among main effects and their interactions for storage root yield over the two years. The stress tolerant indices, correlation analysis, ranking methods, cluster analysis, principal component analysis and biplot analysis were employed to identify drought tolerant genotypes. The stress tolerance index, mean productivity index, geometric mean productivity, yield index and harmonic mean productivity, were found to be the best indicators for identifying high yielding genotypes under both conditions. The genotypes Dhenkanal local-2, 84 × 14, SB21/57, Howrah and S-783 emerged as the most drought tolerant genotypes based on mean rank, standard deviation of ranks and rank sum. The cluster analysis grouped the genotypes into three distinct groups, highlighting SB21/57, S-783, 84 × 14, Dhenkanal local-2, Howrah, 84 × 1, Baster-11 and X-79 in group II as tolerant genotypes. The principal component analysis demonstrated that the first and second components accounted for 99.042 % of the variations. The biplot analysis further confirmed that the genotypes S-783, 84 × 14, SB21/57, Dhenkanal local-2 and 84 × 1 displayed significant drought tolerance. Among all the genotypes, Dhenkanal local-2, 84 × 14, SB21/57, Howrah and S-783 were identified as the most drought tolerant. These genotypes are recommended for breeding for drought tolerance in sweet potato.

Screening Potato Landraces to Cope with Climate Change in the Central Andes of Peru

Agriculture in the Andean region is mainly small-scale and rainfed, especially in Peru where almost 80% of its population depends on agriculture-related activities. Climate change in addition to social factors threatens the food security of this region. The forecast of more frequent dry spells would especially affect potato crops, domesticated centuries ago in the Andes, where there remains a great genetic diversity. This study aimed to characterize the response to drought stress of 79 potato landraces traditionally grown in the Central Andes of Peru (Pasco region) as a first selection for future breeding evaluations. The used indices were mean productivity (MP), geometric mean productivity (GMP), stress tolerance (STI), stress susceptibility (SSI), and tolerance index (TOL), and a scoring methodology that integrates all of them into a single descriptor in a simple and fast way. The varied responses showed a wide genetic diversity within the assessed landraces, where at least nine of them own high resilience and productivity qualities, and many others are highly vulnerable to drought. It is recommended to complement these studies with physiological and molecular evaluations in stress situations, especially in those with tolerance qualities highlighted in this study, and thus promote the conservation of the biodiversity of this region.

Identification of drought tolerant wheat (Triticum aestivum) genotypes using stress tolerance indices in the western terai region of Nepal

Drought is the leading abiotic factor influencing global wheat production. To evaluate the drought performance of wheat genotypes, it is essential to identify and employ stress tolerance indices. These indices are essential for evaluating variation among genotypes in their response to drought, ultimately contributing to the development of more resilient and sustainable wheat production systems worldwide.. Thus, a field experiment was conducted in alpha lattice design with twenty genotypes including three checks viz., Bhrikuti, Gautam, and RR 21 at Institute of Agriculture and Animal Science (IAAS), Paklihawa Campus, Rupandehi, Nepal, under irrigated and drought conditions, to identify drought tolerance wheat in winter season of 2022. In irrigated condition, five irrigations were applied at different critical growth stages. Whereas in drought conditions, only initial irrigation was applied after field preparation, for the germination of seed, and a poly house was constructed, to restrict all forms of natural precipitation. Genotypes were harvested when they attained harvestable maturity, grain yield was recorded, and stress tolerance indices were calculated. The mean grain yield reduction was 86.88 % in drought condition. Correlation analysis showed that Yield under Stress conditions (Ys) had a significant positive correlation with Yield Stability Index (YSI)(0.911**), Geometric Mean Productivity (GMP)(0.918**), and Stress Tolerant Index (STI)(0.911**). Thus, YSI, GMP, and STI are the important stress tolerance indices considered while selecting drought tolerance genotypes. Principal component and biplot analysis revealed that Bhrikuti, BL 5116, NL 1447, NL 1508, and Gautam were stable and high-yielding drought tolerant wheat genotypes.

EMS-induced mutagenesis in Choy sum (Brassica chinensis var. parachinensis) and selection for low light tolerance using abiotic stress indices

BackgroundChoy Sum (Brassica rapa ssp. chinensis var. parachinensis), grown in a controlled environment, is vulnerable to changes in indoor light quality and displays distinct photo-morphogenesis responses. The scarcity of Choy Sum germplasm for indoor cultivation necessitates the development of new cultivars. Hence, this study attempted to develop mutants through chemical mutagenesis and select low-light-tolerant mutants by using abiotic stress tolerance indices.ResultsA mutant population of Choy Sum created using 1.5% ethyl methane sulfonate (EMS) at 4 h was manually pollinated to obtain the M2 generation. 154 mutants with reduced hypocotyl length were initially isolated from 3600 M2 seedlings screened under low light (R: FR = 0.5). Five mutants that showed reduced plant height at mature stages were selected and screened directly for shade tolerance in the M3 generation. Principal component analysis based on phenotypic data distinguished the M3 mutants from the wild type. Abiotic stress tolerance indices such as relative stress index (RSI), stress tolerance index (STI), geometric mean productivity (GMP), yield stability index (YSI), and stress resistance index (SRI) showed significant (P < 0.05), and positive associations with leaf yield under shade. M3-12–2 was selected as a shade-tolerant mutant based on high values of STI, YSI, and SRI with low values for tolerance (TOL) and stress susceptibility index (SSI).ConclusionsThe results demonstrate that mutation breeding can be used to create dominant mutants in Choy Sum. Furthermore, we show that screening for low light and selection based on abiotic tolerance indices allowed the identification of mutants with high resilience under shade. This method should apply to developing new cultivars in other crop plants that can be suitable for controlled environments with stable yield performance.

Identification of Heat Stress Tolerant Wheat Genotype Using Stress Tolerance Indices

This experiment was conducted to identify heat stress tolerant wheat genotypes using stress tolerance indices. A total of twenty wheat genotypes, provided by the National Wheat Research Program (NWRP) in Bhairahawa, were evaluated in both irrigated and heat stress environments. These genotypes comprised three Bhairahawa Lines (BL), fifteen Nepal Lines (NL), and two commercial checks—Bhrikuti and Gautam. The research was conducted at the Institute of Agriculture and Animal Science (IAAS) in Paklihawa, using alpha lattice design. Results showed that the mean grain yield of wheat was reduced by 24.82% under heat stress conditions as compared to irrigated conditions. Notably, mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI), and yield index (YI) exhibited strong and highly significant positive correlations with yield under both irrigated and heat stress conditions. In contrast, tolerance index (TOL) and stress susceptibility index (SSI) displayed negative correlations under heat stress conditions. Genotype NL 1384 exhibited the highest MP, GMP, and STI, closely followed by NL 1417, establishing them as the most stable and productive genotypes. These findings suggest that these genotypes have the potential to be selected for high yields under both irrigated and heat stress conditions. The biplot analysis showed a positive correlation of MP, STI, GMP, YI, and yield stability index (YSI) with yield in the irrigated environment (Ys) and yield in the heat stress environment (Yp), and a negative correlation of stress susceptibility index (SSI), TOL, and reduction (Red). Hence, these indices could potentially be used for the evaluation of wheat genotypes under both irrigated and heat stress conditions.

Analysis of genetic diversity and genome-wide association study for drought tolerance related traits in Iranian bread wheat

BackgroundDrought is most likely the most significant abiotic stress affecting wheat yield. The discovery of drought-tolerant genotypes is a promising strategy for dealing with the world’s rapidly diminishing water resources and growing population. A genome-wide association study (GWAS) was conducted on 298 Iranian bread wheat landraces and cultivars to investigate the genetic basis of yield, yield components, and drought tolerance indices in two cropping seasons (2018–2019 and 2019–2020) under rainfed and well-watered environments.ResultsA heatmap display of hierarchical clustering divided cultivars and landraces into four categories, with high-yielding and drought-tolerant genotypes clustering in the same group. The results of the principal component analysis (PCA) demonstrated that selecting genotypes based on the mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HM), and stress tolerance index (STI) can help achieve high-yield genotypes in the environment. Genome B had the highest number of significant marker pairs in linkage disequilibrium (LD) for both landraces (427,017) and cultivars (370,359). Similar to cultivars, marker pairs on chromosome 4A represented the strongest LD (r2 = 0.32). However, the genomes D, A, and B have the highest LD, respectively. The single-locus mixed linear model (MLM) and multi-locus random-SNP-effect mixed linear model (mrMLM) identified 1711 and 1254 significant marker-trait association (MTAs) (-log10 P > 3) for all traits, respectively. A total of 874 common quantitative trait nucleotides (QTNs) were simultaneously discovered by both MLM and mrMLM methods. Gene ontology revealed that 11, 18, 6, and 11 MTAs were found in protein-coding regions (PCRs) for spike weight (SW), thousand kernel weight (TKW), grain number per spike (GN), and grain yield (GY), respectively.ConclusionThe results identified rich regions of quantitative trait loci (QTL) on Ch. 4A and 5A suggest that these chromosomes are important for drought tolerance and could be used in wheat breeding programs. Furthermore, the findings indicated that landraces studied in Iranian bread wheat germplasm possess valuable alleles, that are responsive to water-limited conditions. This GWAS experiment is one of the few types of research conducted on drought tolerance that can be exploited in the genome-mediated development of novel varieties of wheat.

Index‐based selection of potato (Solanum tuberosum L.) genotypes for tolerance to soil moisture and ambient heat stress

AbstractDeveloping potato varieties that have enhanced tolerance to soil moisture and high‐temperature stress could improve household food and nutrition security in drought and heat prone areas. A field experiment was conducted at two locations in Ethiopia to evaluate the effectiveness of some stress tolerance indices for the identification of drought and heat tolerant potato genotypes. Treatments consisted of two irrigation regimes and 23 potato genotypes. The experiment was laid out as a split‐plot design in a factorial arrangement with three replications. Irrigation regimes were the main plot factor and genotypes were the sub‐plot factor. Stress tolerance indices were calculated based on the tuber yield under stress (Ys) and non‐stress (Yp) conditions of each genotype. To determine the most desirable stress tolerant genotypes, all indices mean rank (R) and standard deviation of the R were computed. Genotypes Cl‐12(CIP‐304371.67), Cl‐13(CIP‐304383.80), Cl‐2(CIP‐302499.30), Cl‐34(CIP‐397079.6), Cl‐15(CIP‐304394.56), and Cl‐14(CIP‐304387.39) were found to have had top mean ranks and higher tuber yield under drought and heat stress. Ranking methods using all indices best determined desirable drought, heat, and combined drought‐heat tolerant genotypes that consistently coincided with the yield rank of genotypes under a given stress condition. This implies that these indices (stress tolerance index, geometric mean productivity, mean productivity, yield stability index, and tolerance index) could be used in combination to differentiate stress tolerances and susceptible potato genotypes. It is recommended that genotypes that exhibited higher drought and/or heat stress tolerance in this study could be further evaluated in drought and heat prone areas for the development of tolerant potato varieties.