To estimate the type and relative amount of genetic variance com
ponents and their interaction with the environment in field bean, the
following traits were studied; flowering date, maturity date, maturity
period, number of branches per plant, plant height, resistance to choco
late leaf spot and rust diseases. A half diaUei F2 set of crosses involv
ing five parental l’ines were evaluated under spaced and dence planting
in two separate experiments. Each of which was grown in a random
ized complete block design with three replicates. Data were recorded
‘ on the base of the individual plant for all traits, and then genetically
analysed by the procedures recorded by Griffing (1956) and Jinks (1954).
Significant densities mean squares were obtained for all the traits
under study. Mean squares for genotypes as weil as its components
reached the level of significance for most traits.
Significant general combining ability . (GCA variance was obtained
for all traits. Also, significant specific combining ability (SCA) variance
was found for all cases except for the number of branches per plant in
the two Sides planting, and the rust disease percentage in one side plant
ing. The magnitudes of the ratios of GCA/SCA revealed that the additive
and additive x additive typés of gene action were the more important
expression for all traits. Interaction of GCA x densities mean squares
were significant for the characters of flowering date, fruiting period,
plant height and percentage of chocolate leaf spot disease. However,
significant mean squares due to SCA x densities interaction were ob
tained for ail traits except that of the number c1f branches per plant
and percentage of rust disease infection.
‘ The parental line N. A. 112 was the best combiner for maturity
date and fruiting period. While, the parental line Equadols seemed to
be a good combiner for resistance to chocolate spot and rust disease
as well as plant height. The most desirable inter-and intra-allelic
interactions were presented in two F21s crosses. The first (Equadols x
Giza 2) for earliness, number of branches per plant, and resistance to
rust disease. The second (N.A. 112 x Romi) for the resistance to
chocolate leaf spot disease. .