Studies on Recombinational Variability for Combining Ability Among F4 Barbadense Lines

Abstract

The present study was aimed at evaluating recombinational variability for combining ability in F4 generation. To assess variability for combining ability, twenty eight F4 (Gossypium barbadense L.) lines were crossed with four common diverse testers (Gossypium hirsutum L.) viz., DH 98-27 (T1), ZCH8 (T2), 178-24 (T3) and DH 18-31 (T4) for use in assessing the variability for combining ability. The entire experimental material was planted on a medium black soil at College of Agriculture, Dharwad under irrigated condition. All the 53 F5 (included Suvin variety as check) barbadense lines, four hirsutum testers and derived F1 crosses along with the straight crosses (Bench Mark Crosses (BMC)) and ruling commercial checks (MRC 6918 Bt check and DCH 32 non Bt check) were sown during kharif 2011 in a Randomized Block Design with two replications and a spacing of 90 cm between rows and 60 cm between the plants within a row. Among the barbadense lines (males), the mean sum of squares (MSS) were not significant for all the characters except mean boll weight, reproductive points on sympodia and seed cotton yield which showed highly significant differences, while number of bolls per plant and ginning outturn exhibited significant differences. Among the hirsutum testers (females) exhibited not significant difference for all the characters except number of bolls per plant and seed cotton yield which recorded highly significant differences, while mean boll weight and transpiration rate showed significant differences. Line x Tester interaction were highly significant differences for number of monopodia per plant, number of bolls per plant, mean boll weight, reproductive points on sympodia, seed index, lint index, photosynthetic rate, stomatal conductance and transpiration rate, while seed cotton yield had significant differences. The estimates of variance due to general combining ability (GCA), variance due to specific combining ability (SCA), the magnitude of SCA variances were greater than GCA variance for all 14 characters and the variance ratio was less than half in these traits, indicating that dominance variance was more than additive variance for these characters. For seed cotton yield, eight lines recorded significant gca effects, of which five lines exhibited positive significant gca effects. The highest gca effect was found by the line DB 533 x DB 534 F4 IPS 8 (363.15). Among the testers, the tester DH 98-27 had positive significant gca effect (94.65) and the tester DH 18-31 showed positive gca effect (35.44), while 178-24 (-77.43) recorded negative significant gca effect. Two crosses manifested positive significant sca effects, of which the cross DH 98-27 X (DB 534 x DB 533 F4 IPS 22) (680.34) recorded the highest positive sca effect. Based on weighted gca method ,the most potential combiners were found to be the lines DB 533 x DB 534 F4 IPS 26, DB 533 x DB 534 F4 IPS 17, DB 533 x DB 534 F4 IPS 8 and DB 533 x DB 534 F4 IPS 32 . Among the testers, the tester DH 18-31 based on weighted gca method is the most potential parent Key word: Recombinational variability, F4 barbadense lines, hirsutum testers, gca, sca