Genotype x environment interactions is of major importance to the plant breeder in developing improved genotypes. When genotypes are compared over a series of environments, the relative rankings usually differ. This causes difficulty in demonstrating the significant superiority of any genotype. This interaction is usually present whether the varieties are pure lines, single cross, double cross hybrids, top crosses, S 1 lines or any other material with which the breeder may be working.

Genetic variability, correlations and path coefficients were studied in desi (Indian) cotton (Gossypium arboreum L.) taking 20 phenotypically diverse genotypes along with two viz., PA-402 and PA-255, one NH-615 and one hybrid check NHH-44. A wide range of variation was found for almost all the characters. All the characters showed very small difference between genotypic coefficient of variation (GCV) and respective phenotypic coefficient of variation (PCV), indicated that all the characters were least affected by environment. The high heritability estimates coupled with high expected genetic advance were observed for number of monopodia plant-1 , number of sympodia plant-1 , plant height, number of bolls plant-1 , average boll weight, lint yield plant-1 , harvest index, oil content, seed cotton yield plant-1 , 2.5% span length and micronaire value indicting the presence of additive gene action and phenotypic selection may be more fruitful. The correlation studies revolved positive and significant genotypic and phenotypic correlation for most of the characters. Considering the association and path analysis, lint yield plant-1 , bolls plant-1 , ginning outturn, lint index, total biomass, number of sympodia plant-1 and plant height had high positive effect on seed cotton yield plant-1 .

The present investigation entitled "Study on heterosis and combining ability for yield, its components and fibre characters in Desi cotton (Gossypium arboreum L.)" was undertaken to estimate general combining ability effects (GCA) of the parents and specific combining ability effects (SCA) of the crosses. The experimental material comprised of 24 F 1 hybrids obtained by crossing 4 lines with 6 testers in line x tester mating system. Sum total of 36 treatments consisting of 24 crosses, 10 parents and three standard checks were sown in Randomized Complete Block Design. The analysis of variance for combining ability revealed significant general combining ability effects (GCA) and specific combining ability effects (SCA) for all the traits.Among ten parental lines, most of the lines were found to be best general combiner, which had significant general combining ability (GCA)effect for seed cotton yield and its contributing characters includingfibre quality traits.Analysis of variance for means revealed significant differences for all the eighteen characters studied. Among females, PA 741 was found to be the best general combiner for 3 characters viz., days to 50 per cent flowering, days to 50 per cent boll bursting and days to maturity had significant GCA effects. The female PAIG 77 was the best general combiner for three characters viz., number of bolls per plant, number of seeds per plant and boll weight. The female PA 809 was the best general combiner for 2.5 per cent span length, fibre fineness/ micronaire, fibre strength, uniformity ratio and short fibre index. Among males, AKA 2004-29 found to be best general combiner for days to 50 per cent flowering, days to 50 per cent boll bursting, days to maturity and ginning outturn. Male parent ARBAS 1301 was also found to be best general combiner for number of sympodia per plant, number of bolls per plant,number of seeds per boll, seed cotton yield per plant, lint index, seed index, plant height, 2.5 per cent span length, fibre fineness, short fibre index and fibre strength. Male parent GAM 162 found to be best genral combiner for ginning outturn, 2.5 per cent span length and short fibre index whereas, CNA 1016 for boll weight. There was close agreement between per se performance and GCA as well as SCA effects for most of the characters. Observations on various characters indicated that the crosses showing high heterosis and high SCA effects had high per se performance and they involved at least one high combining RESEARCHARTICLE INTERNATIONAL JOURNAL OF PLANT SCIENCES

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SUMMARYCotton crop is mainly cultivated for its fibre and hence yield is important in cotton. Cotton crop is highly amenable to both heterosis and recombination breeding as it is often cross pollinated. The present investigation on heterosis studies for yield and yield contributing traits in desi cotton (Gossypium arboreum L.) was undertaken with the objectives to study the extent of heterosis over mid parent (Average heterosis), better parent (Heterobeltiosis) and standard checks (Standard heterosis). In present investigation four lines were crossed with six testers to obtain 24 hybrids in line x tester design. Data were recorded on yield and yield contributing traits. Analysis of variance for means revealed significant differences for all the characters studied. The magnitude of heterosis, heterobeltiosis and standard/economic heterosis for all the characters in the present study were highly appreciable. Among all the characters, the magnitude of heterosis was highest for number of sympodia per plant measuring to the extent of 55.56 %, 47.37 % and 43.59 % over standard check PKVDH 1, PKV Suvarna and NACH 12 in the cross PA 734 x CNA 1016. It was followed by seed cotton yield per plant (48.77 %, 47.44 % and 33.49 %) in the cross PA 734 x ARBAS 1301 over standard check PKVDH 1, PKV Suvarna and NACH 12, respectively.