Deploying reciprocal selection for combining ability for improving performance of hybrids in cotton (Gossypium hirsutum)

Heterosis breeding in cross pollinated crops is supported by Population improvement schemes meant for improving combining ability and these efforts help to increase genetic distance thereby contributing to enhancing heterosis. The procedure defined in such schemes cannot be followed as it is in self pollinated crops and hence these concepts are not employed in self pollinated crops. Earlier some attempts have been made to modify these procedures to suit the mating system in self pollinated crops (Patil and Patil 2003 and Patil et al., 2007). This study gives results of reciprocal selection for combining ability followed In cotton. The procedure of this scheme defined in cross pollinated crops starts with two opposite base populations which have inherent variability that is subjected to exploitation through reciprocal selection for combining ability. In self pollinated crops, firstly opposite groups of genetically diverse groups of genotypes have to be identified in first phase of the present study, seven single crosses from private and public sector were involved in development of 21 double crosses and their evaluation. Based on this evaluation best double cross ZCH-21405 X RAHH-198 was identified and the two single crosses Involved in it were selected as opposite base material and were advanced to F(4) generation for initiating reciprocal selection for combining ability. These opposite population in a segregating generation can act as base population for initiating reciprocal selection for combining ability. Random 23 F(4) lines of cross 1 (ZCH-21405) were crossed with the cross 2 (RAHH-198) as tester, and vice-versa. Evaluation of these 46 derived F(1)'s was done by comparing them with commercial check hybrids and with bench mark double cross. Nature and magnitude of variability among the derived F(1)'s for lint yield was taken as a measure of variability for combining ability and the derived F(1)'s which are superior over the bench mark double cross helped in identifying transgressive segregants for combining ability. The elite combiners of opposite group identified based on reciprocal selection for combining ability in this manner have lead to developing some potential crosses. Apart from utilizing opposite crosses as reciprocal testers, these F(5) lines were also assessed for their ability to combine with additional four varietal testers. Some of these F(5) lines were found to be potential combinations confirming general utility of them as good combiner parents involving other testers.