GENETIC STUDIES IN MAIZE (Zea mays L.)
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Date
2015
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Birsa Agricultural University, Kanke, Ranchi, Jharkhand
Abstract
Maize (Zea mays L.) has been extensively used in the crop improvement researches
using a wide range of genotypes in a wide range of environmental condition. Genetic
diversity analysis of available germplasm lines, type of gene action involved in the
inheritance of yield and yield related traits, screening and characterization of available
genotypes in variable environmental condition are the basic plant breeding approaches
that have been carried out throughout the decades for the improvement of the crop.
Present investigation was done under three major objectives. First, to unfurl the genetic
diversity among maize genotypes based on qualitative and quantitative traits and SSR
markers. Second, study of nature of gene action and interaction in flowering, maturity
and yield traits. And the third, screening of maize lines for drought tolerance using
morpho-physiological traits and estimated stress indices.
Knowledge of germplasm diversity among elite breeding materials has a
significant role in the crop improvement program. Heterosis can be exploited with high
desirability from the cross between two diverse inbreds than narrow ones. Diversity
assessment is carried to elucidate the genetic distance between/among two or more
genotypes so that they can be clustered based on their extent of similarity. A suitable
marker system is of prime importance in diversity assessment based on the purpose of
diversity analysis. In present experiment, twenty maize genotypes grown under the RCBD
were assessed for genetic diversity based on 14 quantitative traits, 9 qualitative traits and
18 SSR based markers to prepare three different UPGMA dendrograms from the
Jacquard’s similarity/dissimilarity coefficients. Different levels of polymorphism were
observed in all the qualitative traits except for kernel colour. Wider range of variation was
observed across the genotypes most influentially on plant height, ear height, days to
tasseling, days to silking and kernel yield per plant. The primer pairs produced 92
different markers with PIC value ranging from 0 to 0.87. Three dendrograms prepared
from three sets of marker system were in no or poor correlation based on the
dis/similarity coefficients. The clustering patterns in different dendrograms were
distinctly different with significant diversity between and within clusters. So, the inbreds
from distinct clusters can be used as parents to exploit high heterosis.
Estimation of the types of gene action involved in the expression of traits, the level
of additive and dominance effects and the heritability in broad and narrow sense are very
important in designing a breeding method for improving the trait of interest. Knowledge
of the way genes act and interact will determine which breeding system can optimize gene
action more efficiently. In the present experiment, a six generation based “Generation
mean analysis” was performed for the five plant traits in three different cross
combinations. Three cross combinations for the study of gene effects in five plant
parameters gave the significant role of different gene action and interactions in different
materials. In days to silking and days to maturity, dominance effect was found to play
predominant role in inheritance. Along with, different types of interactions played
important roles in different crosses. Ear height was found to be inherited through additive
gene action with complex gene interactions. The yield components (cob weight and per
day productivity) were found inherited mainly through dominance action along with
important role of di-genic non-allelic interactions. So, the earliness and higher yield
improvement for the materials under study could be made through hybridization
technique.
The screening of newly developed lines for their performance in variable
environmental conditions has became the major concern over decades to cope with the
several biotic and abiotic stresses prevailing due to global climate change. Superiority in
yield and yield stability throughout the variable moisture status are the major criteria for
screening genotypes as drought tolerant. In this experiment, 100 test genotypes, along
with replicated 3 controls in augmented design grown in two soil moisture levels (viz.
stress and non-stress condition), were compared for their mean yield and yield attributing
traits. A suitable stress index for the drought screening, estimated from the plot mean and
grand mean, were identified. For the stress indices, KiSTI, YI, STI, GMP, MP and DRI
were found to be most suitable for drought screening in maize lines. The results from field
observations and estimation of stress indices showed that morpho-physiological traits and
stress indices could make the suitable criteria for identification of drought tolerant
genotypes. Drought tolerant genotypes identified through average ranking assigned to
them were: 95, 62, 39, 30, 18, 89, 20, 103, and 66. Such identified drought tolerant
genotypes/accessions would make a greatly important breeding material for the future
breeding programs.
Description
GENETIC STUDIES IN MAIZE (Zea mays L.)
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