MSc

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.