Gene action for cane and sugar yield and its component characters in improved populations of Saccharum spp using generation mean analysis

Abstract

Saccaharum spontaneum is a highly polymorphic species known to contribute genes for high tillering, wide adaptability, good ratooning ability and high biomass. Saccharurm officinarum and S.spontaneum were improved through intrapopulation strategy for its yield and quality traits and utilization of the improved clones in pre-breeding program with improved S.officinarum and commercial clones at Sugarcane Breeding Institute, Coimbatore has generated new broadened genetic base population with increased diversity and in identifying heterotic patterns and hybrids. Genetic studies revealed positive high significant heterosis for cane yield (180.00) and cane length %( 96.70) over the standards. The choice of an efficient breeding procedure depends to a large extent on knowledge of the genetic system controlling the character to be selected. Genetic estimates of each character was studied utilizing six parameter model of generation mean analysis to estimate the nature and magnitude of gene effects for cane and sugar yield and its component traits in Saccharum spp . Six basic generations, namely P1, P2, F1, F2, BC1, BC2 of 20 crosses involving 16 diverse parents’ viz., commercial Coimbatore canes, improved officinarum and improved spontaneum were evaluated. Analysis of variance showed significant differences for the traits studied. Joint scaling test revealed both additive and dominance gene effects were highly significant for all the traits in all the crosses except in PIO 88-96 x PIS 38 for cane diameter. Significance of chi-square values were reported for all the traits in eight crosses. Different gene effects were involved in the inheritance of traits studied indicating complex behaviour of genes governing these traits in sugarcane. The mean performance of the F1 indicated dominant gene effect for all the characters. F1 mean values were higher than parental values and F2, BC1and BC2 progenies transgressed the extremes of either parents for the traits under study which indicated dominance interaction. All the traits indicated the inadequacy of simple additive dominance model. The perfect fit model identified (d),(h) and (J) significant for the characters viz., number of millable canes, single cane weight, cane yield and CCS t/ha and opposite signs of (h), (l) indicate the presence of duplicate epistasis which hinders in the expression of heterosis leading to non-exploitation of potential families. The negative (h) for number of millable canes, cane height, cane thickness, cane yield and total sugars in four crosses indicate the role of decreasing alleles which is inherited by dominance. However, two crosses had pronounced effect of i component (additive x additive) for total sugars. Dominance gene effects were most important in governing the yield traits. The negative sign associated with additive (d) and positive sign in association with additive×additive (i) component in three crosses for majority of traits indicate positive additive gene action consisted of positive additive digenic interaction and the balance of the additive gene effects of the genes controlling these traits was negative. Out of interallelic interaction, d x d were pronounced than a x a and a x d interaction. Duplicate type of epistasis was observed for almost all characters studied. Generation mean analysis suggested that both additive and dominance effects were important for most of the traits evaluated in this broad based population, but dominance had a more pronounced effect. The results suggests an improvement strategy combining recurrent selection for additive genetic merit to harness genetic advantage from this broadened genetic base. These recombinants derived from different nobilized groups involving improved officinarum and improved spontaneum will be helpful in sugarcane breeding and provide valuable information for multiple-trait improvement like biomass, fibre ,cane yield, quality and red rot resistance