Heterosis studies for quantitative traits in interspecific hybrids of cotton ( Gossypium hirsutum L . × Gossypium barbadense L . )

Cotton is most important fiber crop of India being a raw material for textile industry and plays a key role in agricultural economy. There are four species of cotton, namely, Gossypium hirsutum L, Gossypium barbadense L., Gossypium herbaceum L., and Gossypium arboreum L. are cultivated all over the world. In India, all the four cultivated species are grown in different zones. The genotypes of G. hirsutum are known for high yielding, whereas the genotypes of G. barbadense are known for fiber quality. The genotypes of cotton having high yield with quality fiber are the demand of farmers. Improvement in relation to yield and other quality characters over the mean of the two parents or over the better parents is known as hybrid vigor. Heterosis is considered as useful when the yield of hybrid increase over the standard commercial check (Meredith and Bridge, 1972). Through heterosis, seed cotton along with quality traits can be improved significantly (Naquibullah et al., 2000). Therefore, the heterosis study is helpful to achieve the high degree of heterotic response by the parents having desirable characters in crop breeding program. Several attempts have been made in the past by various workers in the country for the development of interspecific hybrids (G. hirsutum L × G. barbadense L.) and which have resulted in the release of interspecific hybrids such as Varlaxmi and DCH32 etc. Keeping in mind the economic importance of interspecific hybrids, the present investigation was carried out to develop interspecific hybrids between elite lines of G. hirsutum L. and G. barbadense L. and study the extent of heterosis for yield and yield components.


INTRODUCTION
Cotton is most important fiber crop of India being a raw material for textile industry and plays a key role in agricultural economy.There are four species of cotton, namely, Gossypium hirsutum L, Gossypium barbadense L., Gossypium herbaceum L., and Gossypium arboreum L. are cultivated all over the world.In India, all the four cultivated species are grown in different zones.The genotypes of G. hirsutum are known for high yielding, whereas the genotypes of G. barbadense are known for fiber quality.The genotypes of cotton having high yield with quality fiber are the demand of farmers.Improvement in relation to yield and other quality characters over the mean of the two parents or over the better parents is known as hybrid vigor.Heterosis is considered as useful when the yield of hybrid increase over the standard commercial check (Meredith and Bridge, 1972).Through heterosis, seed cotton along with quality traits can be improved significantly (Naquibullah et al., 2000).Therefore, the heterosis study is helpful to achieve the high degree of heterotic response by the parents having desirable characters in crop breeding program.
Several attempts have been made in the past by various workers in the country for the development of interspecific hybrids (G.hirsutum L × G. barbadense L.) and which have resulted in the release of interspecific hybrids such as Varlaxmi and DCH32 etc. Keeping in mind the economic importance of interspecific hybrids, the present investigation was carried out to develop interspecific hybrids between elite lines of G. hirsutum L. and G. barbadense L. and study the extent of heterosis for yield and yield components.

MATERIALS AND METHODS
In the present study, 12 inbreed lines of G. hirsutum L., namely, RAH1065, PH1075, P2151, GBHV170, SCS793, DHY286, AKH8828, AKH081, PKV RAJAT, LRA5166, PH348, and NH615 and five inbreed lines of G. barbadense, namely.SB289E, Reba-B-50, SUJATA, Sb-425 YF, and Suvin with varying morphological and agronomic characters were selected on the basis of per se performance.The selected 12 lines of G. hirsutum and 5 testers of G. barbadense were crossed in line × tester manner during Kharif 2014 to produce 60 hybrids.The spacing of 90 cm between rows and 60 cm Heterosis studies for quantitative traits in interspecific hybrids of cotton (Gossypium hirsutum L. × Gossypium barbadense L.) between plants was adopted for the crossing program.The resulting 60 hybrids along with 17 parents and 2 standard checks, i.e.MRC 7918 and Varalaxmi were evaluated during Kharif 2015 in a randomized block design (RBD) with three replications each plot consist of two rows of 6 m length.All need-based intercultivation practices were followed during the crop growth period to maintain good crop stand.Observations were recorded on randomly selected five plants in each entry for eight quantitative traits including seed cotton yield per plot for each replication.The mean values were used for estimation of heterosis over mid parent, better parent, and standard checks as per the standard method.The recorded data were subjected to analysis of variance for each of the characters reported by Panse and Sukhatme (1978).Heterosis over mid parent, better parent, and standard check was estimated as per the standard procedure given by Briggle (1963), Fonseca and Patterson (1968), and Meredith and Bridge (1972), respectively.

RESULTS AND DISCUSSION
Analysis of variance (Table 1) revealed significant differences among parents for all the traits.This indicates the presence of the significant variability in the experimental material for the studied traits.The crosses showed significant differences for all the traits which indicate the variability among the crosses for all of the traits.The interaction between crosses and parents also recorded significant differences for all eight characters.This indicates that heterosis could be exploited for all the studied traits.Similar results for most of the traits were reported by Satish et al. (2009), Patil et al. (2010), andDewdar (2013).
In the present study, crosses showing the desirable heterosis for seed cotton yield per plot along with other quantitative traits were identified.Cross RAH1065 × SUJATA showed desirable heterosis for seed cotton yield along with boll weight seed index and days to 50% flowering, while PH1075 × SUJATA also showed desirable heterosis along the traits number of bolls per plant ginning outturn and days to 50% flowering and seed index.Cross PH348 × SUJATA showed desirable standard heterosis for the traits boll weight, lint index, and ginning percent.The cross DHY286 × Suvin showed desirable relative heterosis along with days to 50% flowering, seed index number of bolls per plant.Similar results were found by Patel et al. (2010), Nidagundi et al. (2012), andSolanke et al. (2015).Therefore, these cross combinations, namely, RAH1065 × SUJAL, PH1075 × SUJATA, PH348 × SUJATA, and DHY286 × Suvin may be tested in large scale trail to confirm the superiority for heterosis.

Table 1 : Analysis of variances (mean squares) for eight quantitative traits in cotton
**Significance at 1% level