Abstract
The dissertation work included studies on determination of genetic parameters and gene
effects for ten morpho-physiological traits in six generations emanating from each of six crosses
among four patents. Studies on selection responses with five crosses in Fz and F4 generations were
also the other part of the work. Besides, a solid-seeded trial was conducted with F4 seeds to see the
relationships of grain yield with canopy temperature and leaf senescence. All these experiments
were carried out in late seeding condition. The narrow sense heritability values were found high to
moderately high for 3, 8, 2, 5, 1 and 1 traits out of ten in crosses-1, 2, 3, 4, 5 and 6, respectively.
Estimates of genetic advance were high for tillers/plant, yield/plant and biomass/plant in cross-2
and only tillers/plant and biomass/plant in cross-4. The genotypic and phenotypic coefficients of
variation were high for tillers/plant, yield/plant and biomass/plant in all the six crosses. The six
generations differed significantly for most traits in crosses-1, 2,3, 4 and 5. The additive-dominance
model was suited to account for the variation of spikelets/spike in crosses-2, 4 and 6, 1000-grain
weight in cross-1, plant height in cross-5, grains/spike in cross-6 and harvest index in cross-2,
indicating simpler inheritance pattern for these traits. While digenic epistatic model explained the
genetic variation for other characters, disclosing their response to selection being slower compared
to the above group. Of the four traits considered for studying selection response in F4 generation,
observed response for 1000-grain weight in cross-1 showed closer to and that in cross-3 exceeded
those of the predicted responses. The observed response in F4 generation for yield/plant in crosses-1
and 2 approximated to two-thirds of the predicted ones. Direct and positive responses were found
significant for all four selected traits in the five crosses (except grains/spike in cross-2) of F3
generation, and all but grains/spike in cross-1,yield/plant in crosses-1, 2, 3 and 5 as well as 1000-
grainweight in cross-5 of F4 generation. Selection of grains/spike brought about negative responses
for 1000-grain weight in all the five crosses. Intergeneration correlations between Fâ and Fa aswell as
F3 and F4 were positive and significant for all four traits in cross-2 only. Significant positive
correlation coefficients were obtained between grain yield and canopy temperature depression
(CTd), exhibiting usefulness of the infra-red thermometer machine for measuring CTd. While
significant negative correlations were found between grain yield and plant leaf senescence (PLS),
indicating effectiveness of using PLS as a selection criterion under late seeding condition. Grain
yield of solid-stand and space-plant experiments showed significant positive correlation coefficients,
thereby demonstrating similar yield performance ofthe two methods ofsowing.