IDENTIFICATION OF RICE GENOTYPES WITH ACCELERATING RECOVERY FROM PHOTOPROTECTION AND THEIR GENETIC ANALYSIS
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Date
2023-12-20
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GENETICS AND PLANT BREEDING, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia – 741252
Abstract
Rice cultivation in the eastern and north-eastern parts of India faces biotic and environmental
challenges, including changing climatic conditions and extreme light fluctuations, which reduce
crop yield potential by up to 35-40% in Kharif. The plant undergoes photoprotection mode by
increasing nonphotochemical quenching (NPQ) in high light intensity (>1200 μmole m-2s-1
PPFD ), which attenuates photosystem II yield (ɸPSII) drastically. The plant remains in
photoprotection mode (reduced ɸPSII and high NPQ) even after light intensity becomes normal
(<1000 PPFD) for a more extended period (usually > half an hour). The study aims to identify
rice genotypes with quick photoprotection recovery (QPR) ability and allelic variations of the
genes controlling the traits. However, phenotyping QPR requires more than forty-five
minutes/genotype to measure the chlorophyll fluorescence parameters in progressive actinic light
(200-1800 μmole m-2s-1 PPFD) after dark adaptation. Swarnaprabha, Shatabdi, GB1, and Bidhan
Suruchi showed QPR ability as observed from the less gap between theoretical and observed
ɸPSII yield at 400 PPFD as well as a larger difference between NPQ1800 -NPQ400 after twenty
minutes of exposure at six different increasing PPFD, whereas Swarna, Chotogora, and Srabani
behave contrarily. The study finds that instantly (2 minutes) measured A400/A1800 ratio in 8-10
days old flag leaves strongly associated with NPQ1800 -NPQ400 and ɸPSII400- ɸPSII1800 with R2
value 0.81 and 0.77 respectively. In a panel of ninety-six genotypes using the QPR data by the
newly proposed methodology and 7K SNP genotyping data, GWAS identified that the region
(LOD>3) possesses the genes reported earlier for photoprotection recovery in rice and other
plants. QTL analysis further validated new methodology in a RIL population developed from a
contrasting parental pair Swarnaprabha x IR64. The GWAS and QTL analyze the regions
carrying known photoprotection-related genes like OsPsbS1, OsLUT2, OsVDE, OsZEP,
OsPGPL2, OsbZIP72 located on chromosomes 1, 4, 8, 9. Genotypes with quick photoprotection
recovery identified and further analyzed with existing methodology confirmed their QPR ability.
A positive association between A400/A1800 ratio and yield and biomass was observed in RIL with
R2 values of 0.11 and 0.17, respectively. The newly identified methodology for the QPR will be
used for easier introgression of the traits in popular cultivars of the zone. The identified
genotypes, genes, and QTLs can be used to improve yield potential and allele mining.