Subhashini Selvaraj

The cotton hybrids of seven lines (BSH 18, MCU 5, CO 14, TCH 1828, CO 17, TCH 11199 and Suraj) and five testers (KC2, KC3, GISV 323, GTHV 15–34 and RHC 1409) were raised inRBD for obtaining 35 hybrids. The hybrids along with their parents were studied for traits viz. , mean number of Jassids per plant, injury grade, total phenol content, total reducing sugars, total soluble proteins, trichome length, trichome density and chlorophyll index along with the seed cotton yield per plant. Higher phenolic content, lower reducing sugar, lower soluble proteins, greater chlorophyll index, and higher trichome density would result in fewer jassids per plant. MCU 5 X KC3 hybrid had the lowest injury grade (0.13), highest total phenol content (3.84 mg/g), lowest total reducing sugars (1.14 mg/g), highest chlorophyll index (58.33), lowest trichome length (0.43), highest trichome density (271.42 numbers per centimetre square) and highest yield of 150.74 g/plant. Hence this F ₁ hybrid confers resistance against jassids. Hence, higher phenolic content along with higher trichome density offers resistance to jassids in cotton plants. This cross could be further forwarded to F ₂ to identify the jassid segregants for further screening. Thus, knowledge into these biochemical analyses and trichome density of the cultivar might be used to breed for jassid resistance, which would assist minimise the usage of pesticides and pest loads from the fields, thereby increasing the population's productivity.

The need for mechanical harvesting in cotton production has become paramount as labor costs continue to rise. Efficient machine harvesting requires short and compact cotton plants. This study developed ten F1 populations by crossing five Indian-origin cotton genotypes using a half-diallel mating design. Field trials were conducted in two seasons, Kharif 2022 and summer 2023, at Coimbatore, India. Significant genetic variability was observed across all plant architecture traits, with strong G × E interactions (P ≤ 0.01), highlighting clear opportunities for breeding compact high-yielding cotton types. A consistent negative correlation between plant height and seed cotton yield in both environments suggested that shorter plants provided greater yield stability. An ideal plant height of 75-110 cm was identified as the most suitable for mechanized harvesting. Within this ideal range, architecture traits such as zero monopodia, internode and branch lengths showed a consistent negative association with yield, while plant density, sympodial branch origin and number were positively linked to higher yield. Stepwise regression identified the groups of mainstem internode (1st-4th nodes) and sympodial branch lengths (lower, middle, upper) as key yield-influencing traits, offering targets for breeding compact, high-performing cotton types. Pooled values indicated an ideal mean mainstem internodes lengths (MIL) of approximately 5.2 cm and sympodial branches lengths (SBL) of approximately 19.9 cm, with shorter internodes enhancing plant sturdiness and uniformity, while reduced sympodial length improved canopy openness, light penetration and harvest efficiency with minimal trash intake. The findings provide practical recommendations on compact plant architecture traits, particularly ideal internode and branch lengths, to enhance yield potential and facilitate mechanical harvesting in cotton.

The parents MCU 5, CO 14, CO 17, TCH 1828, KC 2, KC 3, GISV 323, GTHV 15–34 and RHC 1409 of upland cotton were used for the present study. They were obtained from the Tamilnadu Agricultural University, Department of cotton, Coimbatore. Among the 27 primers used only JESPR 154 primer showed amplified fragment at 150 bp which validates the corresponding parents with hairiness trait conferring resistance to Jassid. The hairy nature of trichome density was observed among the resistant genotypes (KC 3, GTHV 15–34, GISV 323 and RHC 1409). Hairiness confers resistance to jassids was evidence from the results and discussion which would confer breeders develop varieties with high resistance genotypes thereby reducing the jassid infestation. The trichomes were found to confer resistance to sucking pests. This henceforth reduce the pesticide consumption in cotton plants thereby paving the way for a safety environment for ecological species without harming them. Pesticide usage would be lowered with the use of tolerant genotypes. It also paves way for the improvement of future integrated pest management (IPM) programme.

The F₂ populations of the crossings CO 14 × NDLH 1938 and CO17 × NDLH 1755 were used to investigate variability and heritability studies in order to better understand the gene action involved in each characteristic studied. Morphological data viz., days to first flowering, plant height (cm), number of sympodials, number of bolls per plant, boll weight (g), ginning outturn (%), upper half mean length (mm), elongation percentage (%) and micronaire value (µg/inch) were all recorded in each plant of both the populations. Studies of heritability and genetic advance as a percent of mean help us determine if a gene is additive or epistatic in nature, and so undergo appropriate breeding programmes for population enhancement. The value of PCV (Phenotypic Coefficient of variation) was always greater than GCV (Genotypic coefficient of variation) indicating the environment also plays a major role in contributing to the variations. The seed cotton yield per plant alone was shown to exhibit additive gene action with high heritability and strong genetic advance as percent of mean, suggesting that it might be used in direct selection since it is the most important attribute for population development.

The present investigation on correlation and path analysis studies helps to study the relationship among the yield and yield contributing traits along with the quality parameters. The observations were taken in the F1 population of 35 hybrids along with lines (7 lines) and testers (5 testers) for the traits viz. plant height (cm), number of sympodial branches per plant, the number of bolls per plant, boll weight (g), lint index (g), single cotton yield per plant (g), ginning outturn (%), upper half mean length (cm), elongation percent (%) and micronaire value (µg per inch). The results revealed that seed cotton yield per plant had strong and positive association with the traits namely number of sympodial branches per plant (0.646), number of bolls (0.633) and boll weight (0.652). Path analysis study revealed that number of sympodial branches per plant (1.5396), boll weight (0.6285), lint index (1.3526) and upper half mean length (0.3392) had high direct positive effects on single plant yield and indirect very high positive effects through the traits viz., number of sympodial branches per plant via., number of bolls per plant (1.5125) and boll weight (1.0121). Hence selection based on these traits that are positively associated and direct positive effect with the yield would produce the best outcome in the genotypes in further breeding programmes.