Title
:
Name of the student
Guide
Degree
Year
Keywords
:
:
:
:
:
Genetic investigations of yield and yield
components in an exotic gene pool of
maize(Zea mays L.)
Habibullah Ahangar
Dr. G.N. Mir
PhD
1997
Zea mays, Genetic variances
ABSTRACT
Pool-40 an exotic germplasm of maize (Zea mays L.) introduced form CIMMYT
was used as the base population to study the nature and magnitude of genetic variances,
genotype x environment interactions, level of dominance and other related parameters
like heritability (in narrow sense) and grains expected to be realized through full-sib
family selection. Bi-parental progenies generated through Design-1 and II of Comstock
and Robinson (1948, 1952) were evaluated under two random environments in an
incompletely Randomized Block Design. Observations were recorded on grain yield per
plant, ear length, ear diameter , kernel rows per ear, 100-kernel weight and other traits
like days to tassel/silk, plant height and ear height.
Comparison of the relative magnitude of the additive genetic variance and
variance due to dominance deviation estimates revealed that additive genetic variance
was more important than the variance due to dominance deviations for all the traits
studied under the two NC designs except for grain yield per plant which showed equal
importance of both these genetic components of variance in the inheritance of this trait.
Negative estimates of dominance variance were confined to Design-1 for days to tassel,
days to silk and ear height. G x E interaction studies revealed that additive genetic
variance was not, in general greatly affected by the environment. On the contrary, the
component of variance due to dominance deviations showed greater interaction with the
environment. This indicated that additive genetic variance was more stable than the other
over the environments. Estimates had higher values in Design-II than in Design-I.
Presence of substantial genetic variability for grain yield in the reference population
revealed that genetic gain (through full-sib family selection) would be around 6.0 to 6.5
per cent per cycle. Comparison of the various estimates obtained through the two NC
designs revealed that the estimates for Design-II are more realistic and therefore,
reliable.
These studies indicated that there is ample scope for improvement of this gene
pool with reference to grain yield and other related traits through some cyclic selection
scheme. Partial to complete lines of dominance exhibited by the traits also offers
opportunities for isolating superior inbred lines for development of hybrids. Besides, the
introgression of some of the traits from this gene pool can broaden the genetic base of
the local germplasm in combating biotic and abiotic stresses.
-o-