Genetic analysis of the duplicate loci, cluster and short branch in Gossypium hirsutum L.

Six generations, namely P1, P2, F1, F2, B1 and B2, of five different crosses involving diverse parents, H14 (Local standard), Res H141 (Reselection of H141), 419/49 (Punjab), 5143C (Ceylon) and Banda-I (Africa) on one hand and PRS-72 a cluster type strain on the other, were studied to gain understanding of the genetics of short fruiting branch and cluster boll bearing in upland cotton, Gossypium hirsutum L. Observations were recorded on cluster vs. noncluster normal plants in the first and second filial and B1 and B2 generations. The segregation ratios of cluster: normal boll bearing in the F2 and B2 (test cross) progenies confirmed that the character is monogenic recessive (cl1cl1) in inheritance. Though the penetrance of the gene which controlled cluster boll bearing was complete, its expression varied. As many as 15 different types of 'cluster' have been described. Length of cluster bearing sympods varied. On average the sympod lengths in PRS-72 and the cluster type F2 and B2 were 2.13 and 4.54 cm, respectively, suggesting influence of specific modifiers evolved in the cluster donor parent and the different genetic backgrounds. It was suggested that there is a dosage effect of modifiers and interaction of homeologous duplicate allele (Cl2 Cl2) in governing the length of the cluster bearing sympods.