ALLELIC VARIATION FOR YIELD AND CULM STRENGTH GENES/QTL’S IN RICE (Oryza sativa L.)
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Date
2018
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PROFESSOR JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY
Abstract
The present investigation is an attempt to evaluate the traits which either directly or
indirectly influence the yield and to validate the reported QTLs/genes for yield and culm
strength in rice germplasm. The experiment was carried out during kharif season of 2017 at
the ICAR- Indian Institute of Rice Research (IIRR), Hyderabad, Telangana. Forty six (46)
genotypes were selected based on the evaluation of 652 rice genotypes in augmented block
design for all the yield traits at ICAR- IIRR during kharif of 2016.
Forty six rice germplasm accessions were evaluated for variability, heritability,
genetic advance, correlation and path coefficient analysis in different yield and yield
contributing traits. The data was recorded on five randomly selected plants for thirteen
quantitative characters. ANOVA and LSD are quite useful in assessing the presence of
variability and significant differences respectively among the test genotypes. The analysis
of variance revealed significant differences for the characters under study, indicating the
presence of genetic variability among the genotypes. For yield attributing traits viz.,
desirable plant height, effective tiller number and panicle length, promising genotypes
could not be precisely selected as LSD analysis revealed overlaps. Promising genotypes for
five major traits viz., test weight, grain number, strong culm, biomass and yield per se traits
have been identified.
The estimates of PCV were slightly higher than GCV for all the characters studied
indicating less influence of environmental factors on the expression of traits. Moderate
estimates of PCV and GCV were observed for days to 50% flowering, panicle length and
harvest index and high estimates were observed for plant height, number of tillers per plant,
number of panicles, panicle weight, grain number, test weight, culm strength, single plant
yield, plot yield and biomass, indicating the possibility for genetic improvement through
direct selection for these traits. Moderate heritability coupled with moderate genetic
advance was observed for panicle length. Characters like days to 50% flowering, plant
height, number of tillers per plant, number of panicles, panicle length, panicle weight, grain
number, test weight, culm strength, single plant yield, plot yield, biomass and harvest index
showed high heritability coupled with high genetic advance as percent of mean, suggesting
that selection for the improvement of these characters may be rewarding. Single plant yield
showed high positive and significant association with tillers per plant, days to 50%
flowering, biomass and productive tillers per plant. Culm strength showed high significant
and positive correlation with culm inner diameter and significant, negative correlation with
days to 50% flowering, indicating that early duration and increased inner culm diameter
would aid in the improved tolerance to lodging. Path coefficient analysis showed
maximum direct contribution towards single plant yield with productive tillers per plant
exerted highest positive direct effect followed by panicle length, number of grains per
panicle, test weight, panicle weight, culm strength, harvest index and biomass. Correlation
and path co-efficient analysis revealed that productive tillers per plant and biomass are very
important traits as selection criteria for effective yield improvement.
Based on Duncan’s multiple range test (DMRT) for least significant differences
among the 46 genotypes, promising genotypes for yield and culm related traits were
identified and validated with reported gene specific markers. Eleven markers were
polymorphic and six were monomorphic. The promising genotypes which had allele
different to the yield-positive control includes KJ 241 for SCM2, GS5 and GS3 alleles, KJ
182 for SCM2, GS5, Gn1a, SPL14 and Ghd7 alleles, KJ 274 for Gn1a, Ghd7 and GS3
alleles, KJ 55 for Gn1a, Ghd7, SPL14 and GS3 alleles, KJ 199 for Gn1a, Ghd7, SPL14 and
GS3 alleles, KJ54 for TGW6, Ghd7 and SPL14 alleles, KJ 251 for GS3 and GS5 alleles, KJ
244 for TGW6 allele, D107 and KJ 263 for GS5 allele and KJ 204 for Ghd7 allele, which
would serve as potential donors for breeding rice cultivars with improved grain yield and
lodging resistance.
For genetic diversity anlaysis, 38 out of 64 markers were polymorphic across all
accessions with an average of 2.2 alleles per polymorphic marker. The PIC value ranged
from 0.07 to 0.51 with an average of 0.31 and marker RM 340 was found to be the most
appropriate marker to discriminate among the rice genotypes owing to the highest PIC
value of 0.51. The cluster analysis showed these genotypes grouping in to eight clusters in
which cluster IA-1 had maximum twenty five genotypes followed by cluster IB and cluster
IA-2. Clusters IIA, IIB, III, V and VII have two genotypes each, whereas the clusters IV, VI
and VIII have only one genotype each. The highest similarity coefficient value was
observed between the cultivar KJ217 and KJ 263 (0.67) followed by KJ 29 and KJ 142
(0.66), KJ 218 and KJ 236 (0.66) and D54 and D63 (0.65), whereas lowest value was
observed for Swarnadhan (0.18) and IFT 200 (0.21), showing highly diverse genotypes.
ANOVA coupled with LSD analysis provides scope for selection of genotypes with
distinctness while ANOVA assesses only the amount of variability. Productive tillers per
plant, culm inner diameter and biomass are considered as important attributes in
formulating selection criterion for achieving desired targets. Analysis of genetic diversity
and allelic variation identified novel sources of genotypes possessing alleles for gene
specific markers that are different from known sources, which would serve as potential
donor for breeding rice cultivars with improved grain yield and lodging resistance.
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D10,302