Heat stress in cotton reduces its productivity. The development of heat-tolerant cotton varieties having resilience against changing climate is feasible. The purpose of this study was to probe the genetic variability in upland cotton for heat tolerance, the association of cell membrane thermostability (CMT), stomata, and trichome size with cotton adaptation to high temperature and effective breeding strategy to advance the valued traits. Relative cell injury percentage (RCI%) in studied genotypes ranged from 39 to 86%. Seventeen genotypes were found heat tolerant on the basis of low RCI%, heat susceptibility index (HSI<1), higher number of boll/plant, and seed cotton yield (SCY). Scanning electron microscopy (SEM) of heat-tolerant genotypes revealed the presence of different size of stomata (21.57 to 105.04 μm2) and trichomes (177 to 782.6 μm) on leaves of selected genotypes. The regression analysis showed a strong and negative association of RCI% and stomata size with SCY. However, no association was observed between the trichome size, yield, and fiber traits. On the overall location basis, a significant genotype × environment interaction was observed. All selected genotypes produced a higher SCY as compared with check varieties. But the stability analysis showed that the high yielding genotypes NIA-M-30, NIA-80, NIA-83, and CRIS-342 were also wide adaptive with unit regression (bi∼1) and non-significant deviation from the regression line (S2d∼0). The ability for the combination of some heat-tolerant genotypes was estimated by using the line × tester method among nine hybrids along with their 3 testers (i.e., male) and 3 lines (i.e., females). Genotypes, CRIS-342 and NIA-Perkh, were observed as best general combiners for SCY with a negative general combining ability effects for RCI%. Five hybrids showed a positive specific combining ability and heterotic effects for studied traits and also found lowest for HSI. RCI% and SCY/plant displayed higher estimates of heritability and genetic advance, indicating the heritability due to additive gene effects and chances of effective selection. The identified heat-tolerant and wide adaptive germplasm can be further advanced and utilized in cotton breeding programs for developing heat-tolerant cultivars. Selection criteria involving CMT and stomata size concluded to be an effective strategy for the screening of heat-tolerant cotton.

Background Sucking insect pests cause severe damage to cotton crop production. The development of insect resistant cotton cultivars is one of the most effective measures in curtailing the yield losses. Considering the role of morphological and biochemical host plant resistance (HPR) traits in plant defense, 12 cotton genotypes/varieties were evaluated for leaf area, leaf glanding, total soluble sugars, total soluble proteins, total phenolics, tannin and total flavonoids against fluctuating populations of whitefly, thrips and jassid under field conditions. Results The population of these insects fluctuated during the growing season and remained above threshold level (whitefly > 5, thrips > (8–10), or jassid > 1 per leaf) during late June and early July. Strong and negative association of whitefly (r = − 0.825) and jassid (r = − 0.929) with seed cotton yield was observed. Mean population of insects were the highest in Glandless-1 followed by NIA-82 and NIA-M30. NIAB-Kiran followed by NIAB-878 and Sadori were the most resistant, with the mean population of 1.41, 1.60, 1.66 (whitefly); 2.24, 2.32, 2.53 (thrips) and 0.37, 0.31, 0.36 (jassid), respectively. The resistant variety NIAB-Kiran showed less soluble sugars (8.54 mg·g− 1), soluble proteins (27.11 mg·g− 1) and more phenolic (36.56 mg·g− 1) and flavonoids (13.10 mg·g− 1) as compared with the susceptible check Glandless-1. Moreover, all insect populations were positively correlated with total soluble sugars and proteins. Whitefly populations exhibited negative response to leaf gossypol glands, total phenolics, tannins and flavonoids. The thrips and jassid populations had a significant and negative correlation with these four biochemical HPR traits. Conclusion The identified resistant resources and HPR traits can be deployed against sucking insect pests’ complex in future breeding programs of developing insect resistant cotton varieties.

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Sixteen newly evolved upland cotton strains developed through conventional and mutation breeding techniques along with two commercial check varieties viz., CIM-496 and CRIS-134 were evaluated two years at five locations in province of Sindh, Pakistan. Information was recorded on seed cotton yield from all location and analyzed statistically. To assess the stability for yield between genotypes and stomata studies was performed. The results from the combine analysis of variance depicted that the mean square for seed-cotton yield for genotypes and genotype x environment interaction (G × E) were highly significant. Genotypes NIA-M-30 showed the maximum seed cotton yield (3.509 ton/ha) with low regression coefficient (b=0.893) and deviation from regression coefficient (S2d=0.015). Other four genotypes viz., NIA-80, NIA-83, NIA-Bt-2 and NIA-Perkh also produced higher yield (3.36, 3.32, 3.31and 3.25 ton/ha respectively) with regression coefficient (b=0.972, 0.918, 0.99 and 0.916 respectively) and deviation from regression coefficient (S2d=0.025, 0.003, 0.00 and 0.024 respectively), indicated wide adaptability to the range of environments. While the cotton genotypes NIA-HM-327, NIA-84 and NIA-HM48 showed high regression coefficient (b= 1.204, 1.331 and 1.291 respectively), which suggest their specific adaptation to favourable environments.

Cotton production requires identification and crop growing of firm cultivars. Genotypes × environment (G×E) interactions are of main concern to plant breeders for rising better and stable strains (Tuteja et Abstract | Trials were carried out to evaluate seed cotton yield stability of cotton lines beneath four diverse climatic conditions. Three strains NIA-94, NIA-95 and NIA-96 and two commercial check varieties in Sindh province of Pakistan viz. Sadori and CRIS-342 were planted under four different locations Tando Jam, Mirpurkhas, Sakrand and Ghotki environment conditions. Seed cotton yield data was recorded from each location and stability analysis (genotype x environment interaction) was performed. The pooled analysis of variance for seed cotton yield, showed highly significant (P< 0.05) differences for varieties, locations and varieties × location interaction. The analysis depicted the significance of both the linear and non-linear components which showed the presence of individually expected and un-expected parts of genotype and environment interaction. Genotypes NIA-95, NIA-94 and NIA-96 produced high average yield (2339, 2280, 2128 Kgha -1 ) respectively having regression coefficient (bi) value 1.68,1.29, and 1.218 which indicated that these genotypes were specifically adapted to favorable environments. While, check variety Sadori with bi (0.98) showed wide adaptation to all environments. CRIS-134 showed regression coefficient (bi 0.714) somewhat close to unity 1.0 can be considered wide adaptable to some extent.