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Three hundred and ninety nine germplasm lines of upland cotton (Gossypium hirsutum L.) were evaluated for fifteen traits to assess the per se performance, magnitude of genetic variability, heritability and genetic advance as percent of mean. Per se performance study revealed the top entries for yield, early maturing, high boll weight, high boll number and fibre quality characters among the 399 entries used for the study. The estimates of PCV were higher than the GCV for all the characters under studied, this shows the influence of environmental factors on the characters. Highest estimates of PCV and GCV were observed for number of monopodia and seed cotton yield. While lowest estimates of PCV and GCV were observed for days to 50% flowering, seed index, bundle strength, uniformity and elongation percent. The four characters viz., number of sympodia, boll weight, lint index and micronaire value showed the moderate estimates of PCV and GCV. High heritability coupled with high genetic advance as percent of mean was observed for number of monopodia, number of sympodia, boll weight, lint index, micronaire value and seed cotton yield and these characters were controlled by additive gene effects, hence selection of genotypes based on these characters would be effective in the improvement of yield.

SVPR 5 is a high yielding long staple hirsutum cotton variety developed by Cotton Research Station, Srivilliputtur. It was released in the year of 2014 and notified during the year 2016 for kharif season of southern zone of India under for winter and summer irrigated tracts of Tamil Nadu. It is a hybrid derivative of the cross between NDLH 1658 and Surabhi. SVPR 5 cotton is semi spreading in nature with determinant growth habit and matures in 150 days. It has recorded a mean seed cotton yield of 1845 kg/ha which is 13.0 % increase over the zonal check Surabhi in AICCIP trials. The overall performance revealed that the cotton culture TSH 0250 was superior over SVPR 2 and SVPR 4 with an average seed cotton yield of 1661 kg/ha against 1583 kg/ha of SVPR 2 and 1425 kg/ha of SVPR 4. Its fibre qualities are comparable to Surabhi with 29.4 mm span length and 22.0g/tex of bundle strength. The cotton SVPR 5 can able to spin to 50s counts which suit the current demand of the textile industries. It is moderately resistant to leaf hopper, bacterial leaf blight, Alternaria leaf spot and grey mildew.

Yield is a complex quantitative character that is controlled by many small genes. For effective and simultaneous selection to improve upon yield of cotton, interaction and contribution of each of the trait parameters has to be understood. The study to understand the relationship of yield components was conducted on sixty hybrids obtained from a cross of ten G. hirsutum and six G. barbadense in a Line x Tester fashion. The study revealed that most of the components were positively correlated amongst each other both genotypically and phenotypically. Number of bolls per plant, Number of sympodial branches per plant and boll weight had positive and high significant correlations with seed cotton yield per plant. In all cases phenotypic coefficient was greater than genotypic coefficient suggesting environmental interference. Partitioning the association into direct and indirect effects indicated that seed index had the highest direct effect on seed cotton yield. For indirect selection, seed index, number of monopodia, number of seeds/boll will be more reliable and 2.5% span length, bundle strength, elongation percent and micronaire also are more reliable for indirect selection for fibre quality in cotton. Six Principal components showed Eigen value of more than one with an accumulated variability of 70.39%. The Principal component with the highest variability was mostly related to seed cotton yield, uniformity ratio, boll weight, number of sympodia, number of bolls/plant and plant height.

Assessment of genetic variability using appropriate parameters like phenotypic coefficient of variation (PCV), genotypic coefficient of variation (GCV), heritability (h2), and genetic advance (GA) are really necessary to start an efficient breeding program. Cultivated tetraploid cotton (G. hirsutum x G. barbadense) hybrids were subjected to variability evaluation, heritability and genetic advance in a randomized complete block design during the summer 2016. The analysis of variance was highly significant for the eighteen characters studied. Elongation % recorded the highest coefficient of variation followed by number of seeds/boll, boll weight, lint index and number of monopodia. Phenotypic coefficient of variation (PCV) recorded higher values than their corresponding genotypic coefficient of variation (GCV) for all the characters, this indicated obviously the presence of environmental interaction in phenotypic expression of the traits. Number of monopodia had the highest PCV and uniformity ratio recorded the least. The highest GCV was recorded by number of monopodia followed by seed cotton yield/plant while least GCV was recorded by days to first bursting followed by 2.5% span length and elongation %. Heritability was expressed very high by seed cotton yield followed by number of bolls/plant. Other characters had high heritability except elongation %, 2.5% span length and days to first bursting which recorded low heritability. The most favourable selection response was demonstrated by number of monopodia and micronaire value. Number of monopodia, micronaire value, lint index and boll weight had demonstrated an additive gene effects by having high heritability and high genetic advance over mean, directional selection would have positive effect for their genetic improvement.

Diallel analysis was carried out by involving nine parents and their 72 cross combinations in upland cotton for assessing their combining ability for yield and its component characters. Variance due to parents and hybrids showed significant differences between all the characters studied except number of bolls, boll weight, single plant yield, lint index and seed index. Significance of variance in parents versus hybrids interaction provides adequacy for comparing the heterotic expression for all the characters except boll weight, ginning per cent, lint index and seed index. The GCA variances were larger than those of SCA for all the traits except number of bolls per plant, indicating the preponderance of additive action. The parents MCU 5 and MCU 7 were proved to be good general combiners for single plant yield and other economic traits and hence need to be included in the yield improvement programmes. The hybrid combinations viz., MCU 5 x MCU 7, Khandwa 2 x Suraj, KC 2 x MCU 5, Anjali x MCU 7 and Anjali x Suraj recorded superior per se performance for number of bolls, boll weight and single plant yield and other characters. Among these crosses KC 2 x MCU 5, Anjali x Suraj and Anjali x MCU 7 exhibited additive type gene action with one good general combining ability parent for number of bolls, boll weight and lint index respectively. Hence, selection can be made in these crosses in early generation itself.