GENETIC STUDIES ON SPIKELET STERILITY AND BREEDING TECHNIQUES OF RICE (Oryza sativa L.)
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Date
2022
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Birsa Agricultural University, Ranchi
Abstract
The present investigation was conducted at the experimental plot of Birsa
Agricultural University, Kanke under the rainfed conditions of Jharkhand, India during
kharif 2020 and 2021 in the F6 and F7 generation seeds of the cross Pusa-1176 x BPT-5204
respectively. The F6 generation plants were particularly examined for the trait spikelet
sterility and plants to be grown in F7 generation were selected based on sterility percentage.
Then, selected plants were sown as panicle to progeny rows at two different dates as set I
and set II with the interval of 15 days in order to study the influence of environment on the
traits under study.
The traits undertaken in the research work for which the observations were
recorded are basically classified into qualitative and quantitative traits. The qualitative
traits include presence of awns, awn colour, leaf sheath colour, stigma colour, leaf margin
colour, apiculus colour and pollen viability test whereas the quantitative traits comprised
of days to flowering, number of tillers per plant, plant height, panicle length, number of
panicles per plant, number of filled spikelet, number of unfilled spikelet, grain length, grain
width, 100 seed weight and seed yield per plant.
The chi-square test revealed that genetic ratios obtained for the segregating
families were monogenic, digenic and trigenic as well for the qualitative traits concluding
that it is governed by single gene, two and three genes respectively depending on the
segregation pattern. It exhibited that the respective segregation ratio of each family showed
dissimilar segregation pattern for both set I and set II in the family no. 42, 44, 62, 83 and
84 for the trait presence of awns, family no. 42, 44, 62, 72, 211, 288 and 309 for awn
colour, family no. 230, 95, 211 and 92 for leaf sheath colour, family no. 42, 309, 72, 211,
83, 275 for stigma colour, family no. 230, 95, 71, 42, 92, 83 for leaf margin colour, and
family no. 42, 71, 230, 72, 82 for apiculus colour that displayed the influence of changes
in temperature and photoperiod. But the respective segregation ratio was found similar in
the family no. 84 and 230 for the presence of awns, family no. 83, 84, 230 and 275 for awn
colour, family no. 309, 44, 42, 72, 83, 275, 84, 82 for leaf sheath colour, family no. 44, 82,
95 for stigma colour, family no. 321, 309, 44, 62, 72, 211, 275, 84, 82 for leaf margin
colour and family no. 321, 309, 62, 83, 211, 275, 92, 84, 95 for apiculus colour concluding
that the behaviour and expression of the concerned genes were found persistent in both the
sets sown and remained unaffected by the environmental fluctuations.
In set I, presence of linkage was detected between presence of awns and awn colour
in the family no. 455, awn colour and apiculus colour in the family no. 42-3, awn colour
and leaf sheath colour in the family no. 455, apiculus colour and leaf margin colour in the
family no. 95-7, 95-14 and 455, apiculus colour and stigma colour in the family no. 42-3,
95-7, 95-14, 230 and 455, apiculus colour and leaf sheath colour in the family no. 95-14,
leaf margin colour and stigma colour in the family no. 42-3, 95-7 and 95-14, leaf margin
colour and leaf sheath colour in the family no. 42-3, 95-14 and 230 and between stigma
colour and leaf sheath colour in the family no. 95-14. Whereas in set II, family no. 83-6
exhibited the presence of linkage between all possible combination of the traits such as
awn color, leaf sheath colour, stigma colour, leaf margin colour and apiculus colour except
presence of awns.
The cytological study of pollen grains via iodine-potassium iodide (I2KI) staining
method revealed that pollen sterility was found to be governed by two genes since it
exhibited digenic segregation ratio. The SSR marker based analysis exhibited segregation
distortion among the genotypes in which amplicons of multiple alleles were found to be
distributed in different segregants. The reported genes linked with the polymorphic
markers were pms4, tms5, rpms1, tms4 and tms8. However, to determine the linked genes
in the present research, sample size should be increased for precise and accurate
assessment.
The results of skewness and kurtosis that mild selection would be sufficient for
improvement in the characters number of panicles, number of unfilled spikelet, 100 seed
weight and seed yield per plant in set I and for days to flowering, number of tillers, number
of panicles and spikelet fertility in set II whereas stringent selection might be deployed for
trait improvement in panicle length and grain length in set I and only for grain length in
set II.
The characters number of tillers, plant height, panicle length, number of panicles,
number of filled spikelet, number of unfilled spikelet, spikelet fertility, grain width, L/B
ratio and 100 seed weight showed highly significant positive correlation with seed yield
per plant in both the sets. But path analysis revealed that number of panicles and number
of filled spikelet exhibited the highest positive direct effect on seed yield per plant in both
the sets among all other characters under study and could be used as selection criteria for
effective improvement of grain yield.
Moreover, few EGMS segregants have been identified from set I such as plant no.
368, 1931, 2071, 2743 based on the cytological study of pollen grains and spikelet fertility.
It showed highly sterile pollen grains but possessed high grain setting indicating high
spikelet fertility, so it might be considered as EGMS segregant and thus could have great
contribution in two-line hybrid breeding of rice.
Furthermore, around 503 out of 2765 segregants from set I and 259 out of 1468
segregants from set II showed higher grain yield in terms of seed yield per pant and have
been recognized as agronomically suitable segregant but further selection among these
agronomically suitable segregant based on L/B ratio would be useful in identifying the
segregant as consumer preferable. Hence, 50 segregants from set I with plant no. 184, 199,
248, 249, 251, 259, 368, 732, 776, 785, 801, 912, 1003, 1013, 1024, 1034, 1125, 1509,
1549, 1611, 1651, 1668, 1714, 1715, 1722, 1749, 1759, 1771, 1791, 1912, 1945, 1999,
2005, 2121, 2124, 2126, 2130, 2131, 2133, 2134, 2135, 2189, 2278, 2540, 2543, 2552,
2557, 2632, 2670, 2687 and 20 segregants from set II with plant no. 47, 58, 76, 117, 422,
621, 679, 784, 981, 1010, 1036, 1082, 1083, 1245, 1249, 1258, 1259, 1345, 1361, 1445
were found to be better performing genotypes . This would be advantageous and beneficial
to the farmers in enhancing the farm produces as well as their income.
However, it is concluded from the result of embryo culture that embryo could be
cultured efficiently at the earliest after 14 days of pollination which might be useful in
overcoming the barriers of wide hybridization and shortening of breeding cycle
consequently leading to rapid generation advancement.