Background: Bottle gourd, a popular winter vegetable in Bangladesh, is experiencing a year-round increase in demand. High temperature stress disrupts physiological structure, fruit quality and crop yields, limiting the year-round cultivation of bottle gourd. The research aimed to identify heat stress-tolerant genotypes to extend growing seasons and increase production among varieties and breeding materials. 
 
Methods: The study conducted at Vegetable Research Center, Dinajpur of BRAC Seed and Agro Enterprise, Bangladesh consisting 58 bottle gourd genotypes under normal and heat stress conditions using augmented block design. Meteorological data showed heat stress resulted ~5-7oC higher air temperatures than normal sowing environments. 
 
Result: Heat stress tolerance indices indicated that the genotypes with a combination of greater values of MP, GMP, HM, YI and STI and lower values of SSI and TOL are high performed and productive breeding material. Yield based stress indices SSI and TOL had a negative association with fruit yield under heat stress (Ys), while strong positive correlations with STI, MP, GMP, HM and YI. The cluster analysis classified bottle gourd genotypes as tolerant, medium tolerant and susceptible to heat stress. Heat stress tolerance indices could be effective tools for identifying heat tolerant bottle gourd genotypes in field. The genotypes BG-45, BG-02, BG-57, BG-39 and BG-43 determined as high performing and stable breeding material under both normal and heat stress environments and might potentially be employed in future breeding programs.

Heat Stress Tolerance Indices and Their Contribution in Identifying Heat Tolerant Bottle Gourd [Lagenaria siceraria (Molina) Standl.] Genotypes

Background: Soybean [Glycine max (L.) Merrill], popularly known as the &ldquo;Golden bean,&rdquo; is a major oilseed crop valued for its high protein and oil content. Soil salinity is a critical abiotic stress that adversely affects germination, growth and productivity in soybean. Identifying salinity-tolerant genotypes remains a key challenge for breeders and seed technologists. Therefore, standardized and reliable screening protocols are essential for the rapid identification of salinity-tolerant genotypes. 
 
Methods: The study was conducted at ICAR-IARI, New Delhi, during the kharif season of 2022 and 2023. A total of 156 soybean genotypes were evaluated, including 150 germplasm accessions (42 black-seeded, 105 yellow-seeded and 3 brown-seeded) with one-year-old stored seeds and six freshly harvested yellow-seeded varieties. Two techniques, namely the top-of-paper method and the between-paper method, were assessed. The top-of-paper method, with application of 2.5 ml NaCl solution on alternate days, was selected as a standard method. Salinity stress was imposed using four NaCl concentrations (0, 3, 6 and 9 dS/m) and seed quality traits [germination, seedling length, fresh and dry weight, Seedling Vigour Indices (SVI-I, SVI-II)] were integrated with the Salt Tolerance Index (STI) for genotypic categorisation. 
 
Result: Significant genotypic variation was observed for seed germination and seed quality under salinity stress. Black-seeded accessions and freshly harvested varieties showed higher germination and vigour than yellow-seeded accessions, which were poor storers. STI correlated positively with vigour indices at 6 dS/m in black accessions and released varieties and at 3 dS/m in yellow accessions. Brown-seeded accessions showed inconsistent responses. Based on STI and correlation, 20 genotypes were categorised as highly tolerant, moderately tolerant, or susceptible. Principal Component Analysis (PCA) identified seedling length and dry weight as key contributors to variation, while MGIDI analysis improved the efficiency of multivariate selection, identifying superior genotypes under both control and stress.The integration of physiological parameters with the Salt Tolerance Index (STI) served as an effective screening method for categorising genotypes into tolerant and susceptible groups. These findingshighlight the importance of using a reliable screening protocol using STI for successful soybean cultivation under salinity stress conditions. 
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Integrating Seed Quality Traits and Salt Tolerance Indices for Efficient Screening of Salinity-Tolerant Soybean [Glycine max (L.) Merrill] Genotypes

Background: Chickpea is a globally important commercial crop and a key source of protein for vegetarian populations. Though chickpea was domesticated at least 3000 years ago, research into abiotic stress tolerance has been limited compared to cereals.&nbsp; 
 
Methods: An experiment was conducted with a set of seventy-one genotypes of Desi chickpea (Cicer arietinum L.) to isolate high temperature tolerant genotypes using randomized block design (RBD) under two different sowing conditions (normal and late/terminal heat stress) and two growing seasons (rabi-2017-18 and 2018-19) at the Pulses Research Station of Junagadh Agricultural University. The screening of heat tolerant genotypes was done based on nine morpho-phenological traits, stress tolerance indices and correlation amongst them.&nbsp; 
 
Result: The heat tolerant genotypes of chickpea had less percentage of reduction in numbers of pods, seed yield per plant and 100-seeds weight. Five genotypes viz., ICC 4958, ICC 14595, ICC 8318, GG 4 and ICCV 92944 were identified as highly heat tolerant on the basis of HSI and YSR. These tolerant genotypes and screening criteria&rsquo;s can be of great importance to identify donor parents to develop new cultivars for the farmers growing chickpea in the heat prone regions.

Evaluation of Desi Chickpea (Cicer arientinum L.) Landraces for Heat Tolerance using Morpho-phenological Traits and Stress Tolerance Indices (STI)

<div>Background: Legumes are under explored crops in comparison to staple cereal crops and decreasing agricultural lands along with waste lands and poor water resources are the main constraints for sustainable agricultural production. Chickpea is the third most important food legume, known for its high nutritive values, generally considered as relatively salt sensitive crop. Existence of large genetic variation provides opportunity to explore variations and exploit the available salinity tolerance in chickpea. &nbsp; 
 
Methods: A Randomised block design experiment was conducted to explore the salinity tolerance in 10 chickpea genotypes including CSG-8962 (Karnal Chana-1), as salt tolerant check during 2018-19 and 2019-20 under control and salinity ECiw 6 dS/m and ECiw 9 dS/m. The leachate was collected from time to time to monitor the buildup of the desired salinity. At harvesting stage, yield and yield attributing traits were recorded and yield indices were calculated to identify the potential of chickpea genotypes against salinity stress. 
 
Result: Saline irrigation water significantly decreased the number of pods/plant by 21.29% under ECiw 6 dS/m and 53.29% under ECiw 9 dS/m. Genotypes ICCV 10, CSG 8962 and DCP 92-3 retained maximum number of filled pods at ECiw 6 dS/m, while under higher salinity of ECiw 9 dS/m, CSG 8962, ICCV 10 and KWR108 had the highest filled pods. Saline water of 6 dS/m caused reduction of 36.1% - 65.0% in grain yield, which further increased to 81.0% - 98.5% with saline water of 9 dS/m. Genotypes S7 and ICCV - 10 had percent grain yield reduction of 36.13% and 41.24% respectively whereas the salt tolerant check had a percent reduction of 46.94% at ECiw 6 dS/m. Based on studied yield indices, genotypes S7, KWR108 and CSG 8962 showed relatively higher tolerance than other studied genotypes, whereas BG 256 and ICC 4463 were the most salt sensitive chickpea genotypes.</div>

<div>Identification of Salt Tolerant Chickpea Genotypes Based on Yield and Salinity Indices</div>

<div>Background: Drought and moisture stress is the most limiting factor affecting growth and productivity of crop plants. The genotypes may differ in their ability to withstand drought or moisture stress. Therefore, the research was carried out to identify suitable genotypes in moisture stress environments.&nbsp; 
 
Methods: The forty eight genotypes of fenugreek were planted in randomized block design with three replications under two environmental conditions namely, (i) normal irrigation (E1) and (ii) staggered irrigation (E2) during rabi 2016-2017. Eight stress tolerance indices viz., stress tolerance (TOL), stress susceptibility index (SSI), stress tolerance index (STI), mean production (MP), geometric mean production (GMP), yield index (YI), stress susceptibility percentage index (SSPI) and modified stress tolerance index (MSTI) were calculated based on seed yield under moisture stress (Ys) and non-stress condition (Yp). The correlation coefficient and mean rank of stress indices were calculated to identify the moisture stress tolerant genotypes.&nbsp; 
 
Result:&nbsp;The seed yield under non-stress condition (Yp) had significant positive association with TOL, SSI, STI, MP, GMP, SSPI and K1STI. The seed yield under stress condition (Ys) had significant positive association with STI, MP, GMP, YI and K2STI, while significant negative association with TOL, SSI and SSPI. The results showed that MP, GMP and STI indices were more effective in identifying high yielding genotypes in both stress and non-stress conditions while TOL, SSI, YI and SSPI under moisture stress condition. Based upon the mean seed yield and stress tolerance indices, the genotypes UM-124, UM-60, UM-55, UM-28 and UM-4 were found tolerant to staggered irrigation conditions. Hence, these genotypes may be used further in breeding programmes for moisture stress tolerance.</div>

​​Assessment of Multiple Tolerance Indices for Moisture Stress in Fenugreek (Trigonella foenum-graecum L.)

<div style="text-align: justify;">Breeding for water stress tolerance is very difficult as the stress conditions created in experimental set up and actual field conditions, invariably, have poor correspondence. Direct selection for yield under stress holds promise but is slow on account of complexity of yield. Screening based on yield suffers from low heritability. Yield has been the primary breeding objective in production breeding and has been improved either by targeting yield per se as well as yield components based on correlated response. Drought stress indices are quantitative measures that characterize water stress response by yield data from one or several environments based on timing, duration and intensity of stress. Such an index is more readily useable than raw yield data. Since drought resistance is a yield based trait, selection could vary depending on which index is chosen by the breeder. A major drawback of using these indices has been lack of correspondence in rankings across indices and their failure to discriminate overlapping responses in terms of yield under stress. There has been substantial effort on part of scientists to develop and validated different indices based on yield per se, index scores, regression analysis as well as various model based approaches. The major focus has been on identifying variables such as phenology, physiological traits, biomass partitioning or other parameters that influence crop performance under stress. The paper appraises the approaches from yield based indices to regression based as well as crop model based that have been used to understand crop response to water stress.</div>

Stress tolerance indices based on yield, phenology and biomass partitioning:&nbsp;A review

<div>Background: Detection and quantification of variability among germplasm accessions/segregating populations/advance breeding lines is a pre-requisite (among others) for breeding crop plants for drought tolerance. Indices that integrate yield under moisture stress free (MSF) and moisture stress (MS) have been developed and used for screening and selection of moisture stress tolerant genotypes in several crops. The present study was aimed at identifying desirable indices from among those reported for screening and selection of terminal moisture stress (TMS) tolerant genotypes.&nbsp; 
 
Methods: Two experiments were conducted at experimental fields of Department of Genetics and Plant Breeding, University of Agricultural Sciences Bengaluru during 2017 post rainy season. The first experiment consisted of 33 genotypes which included 31 selected genotypes from F3 populations and two released varieties. The second experiment consisted of 13 genotypes which included 5 advanced breeding lines, 2 released varieties and 6 land races. The genotypes of both the experiments were evaluated for dry seed yield under two moisture regimes (MR), namely, MSF and TMS environments in separate trials following Randomized Block Design.&nbsp; 
 
Conclusion: Based on the criterion of significant correlation of indices with dry seed yield under both MSF and TMS environments, two indices namely, mean productivity (MP) and geometric mean productivity (GMP) were found desirable to identify TMS tolerant genotypes of both the experiments. Based on rank mean of the two indices, two F3 selections and one released variety from first experiment; four landraces, one advanced breeding line and one released variety from second experiment were found TMS tolerant.</div>

<div>Identification of Indices for Empirical Selection of Dolichos Bean [Lablab purpureus (L.) Var. Lignosus] Genotypes for Tolerance to Terminal Moisture Stress</div>

<div>In present global climatic scenario, heat stress is one of the prime problems affecting production of mungbean crop during summer. A major ob&shy;jective of mungbean breeding programs to increase genetic potential of genotypes under heat stress environments. In order to identify heat tolerant promising lines, a total of 35 genotypes were evaluated in normal and heat stress environments during 2012-2013. Eight heat indices were used on the basis of grain yield in normal and heat stress environment. Highest significant positive correlations were observed among mean productivity, Geometric mean productivity, stress tolerant index and yield indices under both normal and heat stress environments. Based on 3-D plot, the genotypes i.e. SML 1186, NDM 12-308, IPM 02-4 and Smrat were found with high stress indices score and could be utilized in mungbean breeding programs to introduce and develop the heat tolerant promising varieties. &nbsp;</div>

<div>Investigating stress indices to discriminate the physiologically efficient heat tolerant genotypes of mungbean [Vigna radiata (L.) Wilczek]</div>

Background: Drought is a major problem reducing agronomic crop production worldwide. Increasing the genetic potential of yield in water deficit condition is one of the major objectives of durum wheat breeding programs in world. 
 
Methods: In this study, 20 genotypes of durum wheat (Triticum durum Desf.) were assessed in both water-stressed and well-watered environments for 2 years i.e. 2017-18 to 2018-19 rabi season. In each environment, each genotype was sown in four rows of 2.5-meter length and 20 cm apart using a randomized complete block design with two replications. Eight drought tolerance indices were applied based on grain yield in drought stress (Ys) and normal irrigation (Yp) conditions. Highly significant differences for yield (Yp and Ys) and all drought tolerance indices were observed indicating differences in genotypes for genes controlling yield and drought tolerance indices. 
 
Result: High yield values in non-stress and stress environments were exhibited by genotypes GW 1339 (8254.29 kg ha-1, 2970.83 kg ha-1) followed by GW 2017-864 (7512.50 kg ha-1&nbsp;2756.25 kg ha-1) and HI 8737(7186.47 kg ha-1, 2845.83 kg ha-1). It is remarkable that the genotypes GW 1339, GW 2017-864 and HI 8737 had high performances in both stressed and non-stressed conditions for grain yield. The maximum value of STI (0.576), HARM (4329.06) GMP (4922.03), MP (5612.56) and YI (1.28) indices was manifested by genotype GW 1339. Based on different drought indices, genotypes GW 1339, GW 2017-864 and HI 8737were found promising for drought tolerant than the other genotypes. The STI, HARM, GMP and MP indices, which were strong positive and significantly correlated to the grain yields in both favorable and drought stress environments, were introduced as the best indices, indicating effectiveness of these indices in identifying high yielding lines under drought stress as well as non-stress conditions. Association studies indicated that there was a positive and non-significant correlation between (Yp) and (Ys) was observed. The SSI index exhibited a negative correlation with the yield (Ys) under stress environment.&nbsp;Results of association studies showed that STI, HARM, GMP and MP indices were able to discriminate between drought-sensitive and drought-tolerant durum wheat genotypes.&nbsp;Principal components analysis showed two components which explained 99% variation.

Assessment of Durum Wheat Genotypes by Drought Tolerance Indices under Drought and Normal Condition

<div>Background: The exposure of field pea crop to high-temperature stress during the anthesis and pod development stage led to poor pollination, development of shriveled pods and poor performance that results in reduced seed yield. The study aims to screen and identify heat-tolerant genotypes based on stress tolerance indices. One hundred forty-three field pea genotypes, including three checks evaluated in augmented block design for seed yield per plant under normal and late sown conditions to identify terminal heat-tolerant genotypes of field pea.&nbsp; 
 
Methods: Stress indices were computed based on seed yield per plant under normal (Yp) and late (Ys) sown conditions. The stress indices for seed yield are calculated as per the suggested method i.e. tolerance index (Hossain et al., 1990), heat susceptibility index (<a href="#fischer_1978">Fischer and Maurer, 1978</a>), yield stability index (<a href="#bouslama_1984">Bouslama and Schapaugh, 1984</a>), mean productivity (Hossain et al., 1990), geometric mean productivity (Fernandez, 1992), stress tolerance index (<a href="#fernandez_1992">Fernandez, 1992</a>). Correlation coefficient and principal component analysis were done by using R (version 4.1.1) statistical software.&nbsp; 
 
Result:&nbsp;Correlation coefficient analysis reveals that seed yield under stress conditions was positively correlated with the indices viz., MP, GMP, STI and YSI whereas, it was negatively correlated with HSI, signifying that higher estimates of MP, GMP, STI and YSI and lower of HSI correspond to heat tolerance. The seed yield under both environments had a positive and significant association with MP, GMP and STI. Genotypes viz., EC-341743, P-1679, P-1384-3, P-179 and P-781 were found with high indices scores and showing their suitability for the breeding program for heat tolerance. The first two principal components (PCs) accounted for 97.46% of the total variation present in the genotype.</div>

Heat Stress Tolerance Indices and Their Contribution in Identifying Heat Tolerant Bottle Gourd [Lagenaria siceraria (Molina) Standl.] Genotypes

Integrating Seed Quality Traits and Salt Tolerance Indices for Efficient Screening of Salinity-Tolerant Soybean [Glycine max (L.) Merrill] Genotypes

Evaluation of Desi Chickpea (Cicer arientinum L.) Landraces for Heat Tolerance using Morpho-phenological Traits and Stress Tolerance Indices (STI)

Identification of Salt Tolerant Chickpea Genotypes Based on Yield and Salinity Indices

Assessment of Multiple Tolerance Indices for Moisture Stress in Fenugreek (Trigonella foenum-graecum L.)

Stress tolerance indices based on yield, phenology and biomass partitioning: A review

Identification of Indices for Empirical Selection of Dolichos Bean [Lablab purpureus (L.) Var. Lignosus] Genotypes for Tolerance to Terminal Moisture Stress

Investigating stress indices to discriminate the physiologically efficient heat tolerant genotypes of mungbean [Vigna radiata (L.) Wilczek]

Assessment of Durum Wheat Genotypes by Drought Tolerance Indices under Drought and Normal Condition

Application of Stress Indices to Identify Terminal Heat Tolerance Genotype in Field Pea (Pisum sativum var. arvense)