STUDIES ON COMBINING ABILITY AND BLAST RESISTANCE IN HYBRID RICE (Oryza sativa L.)
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Date
2015
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PROFESSOR JAYSHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD
Abstract
The present investigation entitled “Studies on Combining Ability and Blast
Resistance in Hybrid Rice (Oryza sativa L.)” was undertaken to identify the effective
restorers and maintainers among the elite lines. Based on the results, 12 parents were
selected and mated in line × tester mating design to study the combining ability and
magnitude of heterosis of experimental hybrids for grain yield per plant and yield
contributing characters in Telangana.
Out of 23 lines screened for restorer and maintainer reaction 12 lines exhibited
very high spikelet fertility (>75%), 8 lines exhibited partial fertility (50 to 75%),
3 lines resulted low fertility (0.1 to 50%) and none of the lines recorded complete
sterility (0%). Based on the results, 12 R lines were identified as male parents and
crossed with three CMS lines (IR 72081A, IR 68902A, IR 58025A) in line × tester
mating design resulting in 36 hybrids. The 15 parents, 36 hybrids and a hybrid check,
PA-6129 were evaluated at Rice Research Centre, Rajendranagar of Telangana during
Kharif 2014 for combining ability and heterosis. Further blast screening experiment
was done during Rabi 2014-15, using the checks, IR-64 and TN1.
The analysis of variance for grain yield and yield contributing characters revealed
significant difference between the treatments for all the characters under study
indicating that there was sufficient variability among the lines tested. Hence, combining
ability analysis was carried out.
The analysis of variance for combining ability revealed significant difference
between the treatments for grain yield per plant and all the component traits, thus
justifying their use in the present investigation. Similarly, hybrids also varied
considerably between themselves, suggesting the wide variability among the crosses.
The parents vs crosses were significant for all the characters studied except panicle
length, number of unproductive tillers per plant and grain length-breadth ratio.
Significance of parents vs crosses indicates that significant heterosis is observed for
these traits. Further, crosses partitioned into lines, testers and lines × testers. The lines were found significant for all the characters; the testers were significant for majority of
characters except panicle length, flag leaf width and spikelet fertility per cent; while the
interaction between lines and testers were significant for all the traits studied which
suggests sufficient variability.
On the whole, based on the mean performance, GCA effects and SCA effects, IR
72081A was best among the testers while among the lines, MTU 1010, RNR 15038 and
IR 64 performed better. Among the hybrids IR 58025A × MTU 1010, IR 68902A ×
RNR 15038 and IR 72081A × RNR 15038 performed superior to check PA 6129 in the
present investigation.
Heterosis for single plant yield is mainly because of simultaneous manifestation
of heterosis for yield component traits. Out of 36 hybrids studied, the significant
standard heterosis is observed in 3 hybrids viz., 58025A × MTU 1010 (18.25), IR
68902A × RNR 15038 (14.59) and IR 72081A × RNR 15038 (9.57) over the hybrid
check, PA 6129.
From the blast screening experiments by UBN (Uniform Blast Nursery) method,
it was found that 22 hybrids and 5 parents are resistant to screening reaction; 14 hybrids
and 7 parents are moderately susceptible; and 3 parents are highly susceptible to the
blast disease. The parents which showed resistant reaction were IR 64, NLR 33358,
KNM 118, RNR 15048 and RNR 15038 which can be used as parents for development
of blast resistant varieties and hybrids. Among the top 10 hybrids with high yielding
per se performance, 8 hybrids showed resistant reaction. The best hybrids identified
with blast resistance are, IR 72081A × MTU 1010, IR 72081A × IR 64, IR 72081A ×
RNR 15038, IR 72081A × RNR(RK) 28, IR 72081A × RNR(RK) 53, IR 68902A × IR
64, IR 68902A × RNR 15038 and IR 58025A × MTU 1010.
Character association and path analysis revealed that the traits viz., productivity/
day, days to 50 per cent flowering, grain length, number of productive tillers per plant,
panicle weight, number of filled grains per panicle, 1000 grain weight, flag leaf width
and flag leaf length have direct positive effect on grain yield per plant. Therefore, it is
suggested that preference should be given to these characters in the selection
programme to isolate superior lines with genetic potentiality for higher yield in rice
genotypes.
From this study, three hybrids viz., IR 58025A × MTU 1010, IR 68902A ×
RNR 15038 and IR 72081A × RNR 15038 were identified as best hybrids with high
significant standard heterosis for grain yield and yield contributing characters, high
SCA effects and blast resistance. These hybrids are recommended for further testing
over locations and seasons, for stable performance.
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Keywords
grain, hybrids, developmental stages, planting, yields, heterosis, rice, productivity, fertilizers, biological phenomena