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Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Dist. - Nadia, West Bengal PIN - 741 252

The university established in 1974, has completed five decades of its existence as the pioneer institute of Agricultural Education, Research and Extension. The main objective of this Viswavidyalaya is to provide facilities for the study of Agriculture, Horticulture and Agricultural Engineering. It is also to conduct researches in these sciences and undertake the educational and extension programmes in agriculture among the rural clientele base, keeping in view the requirements of the state.

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Subject: Genetics and Plant Breeding × Author: K. Nimitha × Start date: 2005 ×
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    ThesisItemOpen Access
    GENETIC ANALYSES ON LEAF AREA EXPANSION AND YIELD OF RICE UNDER LOW LIGHT INTENSITY
    (GENETICS AND PLANT BREEDING, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia – 741252, 2023-10-04) K. Nimitha; Dr. Somnath Bhattacharyya
    The rice yield potential is adversely affected by the declined light intensity caused by the seasonal clouds in the wet season spanning from July to October. The mean solar radiation is immensely reduced in the wet season (<500 μmol m-2 s-1) compared to the dry season (1000 μmol m-2 s-1). This menacing effect of low growth irradiance is reflected in the considerable yield gap between eastern India’s dry and wet seasons (5.1 tones ha−1 vs. 2.8 tones ha−1). Moreover, low light irradiance harms grain quality, grain appearance, milling and eating quality, seed set percentage, and total dry matter production. Therefore, to secure a hunger- free world, there is a great necessity to assuage the low-light-stress consequences on rice productivity. No universal shade tolerance mechanism is observed in earlier studies; instead, genotypic-specific plasticity reduces yield loss. As the leaf area has a decisive role in improving photosynthesis and grain yield, it is imperative to know whether the shade-tolerant genotypes can modify leaf traits to improve the net assimilation rate and grain yield, even at 400 μmol m-2 s-1. The study observed a considerable variation of leaf-area expansion (LA) and specific leaf weight (SLW) reduction and the improvement of the net photosynthesis rate at 400 μmol m-2 s-1 (A400) in a set of twenty-five low light grown rice (35% light cut using the white net) genotypes compared to ambient-grown. Reduced SLW exhibited a higher A400 and grain yield reduction in lowlight adapted plants. Enhanced A400 in shade-adapted leaves is mainly due to intercellular CO2 concentration enhancement. Although the Chl a/b ratio improved in shade-grown plants, they correlate neither with high A400 nor with yield. So, SLW reduction ability could be a selection criterion for improving yield under low light intensity. A shade-responsive SLW reduction and leaf area expansion QTL, qSLWR1.1, was identified between 37.83- 38.84 Mbp on the Chromosome 1 in two consecutive years when mapping was done using genotypic data of one hundred thirty RILs by nine hundred twenty- seven polymorphic SNPs between Swarnaprabha and IR64. It explained 13.34% and 19.94% of the SLW reduction with a LOD of 4 and 10 in two consecutive years. However, the IR64 allele for qSLWR1.1 is desirable compared to Swarnaprabha for SLW reduction in the shade. The same QTL was also responsible for the leaf area expansion in the shade, explaining almost 20% variation in both years with average additivity from Swarnaprabha. Based on the shade responsiveness, when the nucleotide sequence of one peptide transporter gene, Os01g0872500, located within the newly identified QTL, was compared, an eight-nucleotide deletion in exon 1 of IR64 was observed compared to Swarnaprabha. In a RIL population developed from Swarnaprabha x IR64, 8nt deleted IR64 allele showed a significant association with yield loss alleviation with R2 value 0.12. Thus, the QTL and the allelic variant of the peptide transporter gene identified in this study can be used in improving yield where lowlight is a constraint, like vast eastern and northeastern India.