Genetic evaluation of F4 and F5 generations of irradiated interspecific hybrids in okra(Abelmoschus spp.)

Abstract

A study was undertaken in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during 1997-98 for the genetic evaluation of the F 4 and F 5 generations of irradiated interspecific hybrids between A. esculentus and A. manihot with the objective of isolating high yielding yellow vein mosaic disease resistant lines from the segregating generations. The families in the F 4M4 generation were found to be late flowering and recorded higher mean values for number of leaves, number of branches, number of flowers and number of fruits per plant compared to the cultivated parent. The fruit yield per plant was higher than the parents inspite of the reduction noticed in average fruit weight. The families recorded lesser values for fruiting phase and duration and higher values for plant height. The crude fibre content of the fruits, yellow vein mosaic incidence and shoot and fruit borer infestation were lower in the families. This provided scope for the selection of several high yielding and YVM disease resistant types from the F 4M4 generation Number of flowers per plant and incidence of YVM disease recorded high phenotypic and genotypic coefficients of variation. High heritability and genetic advance were observed for leaf number and weight of fruits per plant. Fruit yield per plant had high positive correlations with leaf number, number of branches, number of flowers and fruits per plant and plant height. Hence effective selection can be done for these characters for yield improvement.

In the F sMs generation, the families were early flowering and recorded increase in leaf area, pollen sterility and number of branches per plant. The families also recorded higher mean values for leaf number, number of flowers and fruits per plant and plant height compared to the parents. The fruit yield per plant, average fruit weight and number of seeds per fruit were higher in the F sMs families. The fruiting phase and duration recorded an increase while the crude fibre content of fruits, incidence of YVM and incidence of shoot and fruit borer recorded lower mean values. Incidence of YVM disease had the maximum phenotypic and genotypic coefficients of variation. High heritability and genetic advance were observed for yield of fruits per plant. Weight of fruits per plant was significantly and positively correlated with leaf number, number of branches, number of flowers and fruits per plant, average fruit weight and plant height. Selection based on these characters will be effective in improving the yield of the crop. At the same time, high variation noted for YVM disease incidence offers more scope for selection based on disease incidence, in the process of selection for high yielding disease resistant types.