GENETIC STUDIES ON PHYSIOLOGICAL AND AGRONOMIC TRAITS SUITABLE FOR DIRECT SEEDING IN RICE (Oryza sativa L.)
Loading...
Files
Date
2017
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Acharya N.G. Ranga Agricultural University
Abstract
Rice is commonly grown by transplanting seedlings into puddled soil.
Puddling and transplanting require huge amounts of water and labour, both of
which are becoming increasingly scarce and expensive, making its production less
profitable. Under the situation of water and labour scarcity, farmers are changing
their crop establishment method transplanting to direct seeding. This rambles the
need of varietal improvement for traits viz., early seedling vigour for weed
competitiveness; anaerobic germination and tolerance of early submergence;
dense root system for drought resistance and culm thickness for lodging
resistance, which are highly essential for good crop establishment in direct
seeding conditions.
Present investigation was aimed to characterize the elite rice cultivars for
the traits related to direct seeding and yield; to work out the genetics of the traits
related to direct seeding by using established molecular markers.
The genetic variability studies revealed that significant differences among
the genotypes for all the 19 characters studied indicating the existence of high
degree of variability in the material. The estimates of heritability and genetic
advance as per cent of mean were high for the characters viz., days to 50%
flowering, plant height, leaf area index, number of productive tillers per plant,
total number of tillers per m2
, test weight, grain yield per plant, biological yield
per plant, seedling root length, seedling shoot length, seedling vigour index and
basal culm diamter.
Genetic diversity among 48 elite rice cultivars for direct seeding traits was
determined using 10 SSR markers (two each for the five direct seeding traits viz.,
Anaerobic germination, seedling root length, seedling shoot length, rate of
germination, culm diameter) and estimated magnitude of genetic diversity for 19
agronomic and physiological traits viz., days to 50% flowering, plant height (cm),
leaf area index, number of productive tillers per plant, total number of tillers per
m
2
, panicle length (cm) number of filled grains per panicle, number of total grains
per panicle, spikelet fertility (%), test weight (g), grain yield per plant (g),
biological yield per plant (g), seedling root length (mm), seedling shoot length
(mm), vigour index and basal culm diameter (mm) with D2
analysis. All the ten
SSR loci were polymorphic and produced 36 alleles. The number of alleles per
locus generated by each marker varied from 2 to 5 alleles with an average of 3.6
alleles per locus. Polymorphic information content (PIC) of these markers ranged
from 0.305 to 0.797 with an average of 0.628 indicated potentialities of these
markers for assessing genetic diversity. Based on molecular diversity and D2
analysis seven parents (MTU 3626, MTU 1010, MTU 1121, MTU 1140, PS-140-
1, AC39416A) were selected and crossed in Griffing’s diallel fashion (Method-2,
model-I) during Rabi, 2014-15 to generate 21 F1s.
Evaluation of the 21 F1s along with parents was done in kharif, 2015-16.
The ANOVA for combining ability revealed that parents and crosses had
significant amount of variability for all the characters. The component of variance
due to both gca and sca were significant for all the characters studied indicating
the role of both additive and non-additive gene actions in governing the
inheritance of these traits. Among the seven parents studied for their combining
ability pertaining to nineteen different characters, the line, PS-140-1 recorded
significant gca effects in desirable direction for majority of the characters
followed by AC39416 A, MTU 1121, MTU 1140 and MTU 1156. Heterosis
studies revealed that 15 out of 21 crosses registered significant positive heterosis
over both mid and better parents for grain yield per plant. The best heterotic
combination identified were MTU 3626 × PS-140-1 for important yield
contributing traits; MTU 1140 × AC39416 and MTU 1140 × PS-140-1 for direct
seeding traits.
In the present study, an effort was also made to generate genotyping data of
two F2 populations viz., MTU 3626 × PS-140-1 and MTU 1121 × PS-140-1 (100
individuals each) using the 10 SSR markers which were used earlier for screening
of genotypes for direct seeding traits. The markers that linked to anaerobic
germination (RM341, RM206); seedling root length (RM201, RM234); seedling
shoot length (RM17, RM263): rate of germination (RM231) and culm diameter
(RM20557, RM5509) were segregated in expected genetic ratio i.e., 1: 2: 1 for
which the χ2 values were non significant against table value. The marker RM7,
linked to rate of germination showed segregation distortion for the cross MTU
3626 × PS-140-1 progeny by not segregating in the expected genetic ratio 1:2:1
and showed high, significant χ2
value. The results revealed the usefulness of the
studied SSR makers in marker assisted selection of direct seeding traits.
Description
D5436
Keywords
null