Genetic and molecular analysis of basmati x indica (Salt tolerant) derived segregating population(s) in rice (Oryza sativa L.)
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Date
2018
Authors
Mahavir
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Publisher
CCSHAU
Abstract
Experiments were carried out to develop and assess segregating population(s) for variation in salt tolerance and physio-morphological traits derived from two crosses, Pusa1121 x CSR10 and Pusa1121 x Pusa Basmati 1460 (PB1460). A novel selection strategy was used for screening segregating populations for salt tolerance at seedling stage; seven-day old germinated seedlings were subjected to 40 mM NaCl treatment in Yoshida nutrient solution for 3-7 days in the net-house, which allowed the selection of most salt tolerant segregating genotypes. Selected salt tolerant F2 (3 plants), F3 (64 plants), F4 (12 plants) and BC1F1 (21 plants) seedlings of the two crosses had values/scores for salinity tolerance related parameters including root length (7.6 – 13.6 cm), shoot length (13.0 – 24.4 cm), fresh weight (0.351 – 1.214 g), Na+ (4.14 – 6.16 μmoles/g DW) and K+ contents (37.35 – 75.35 μmoles/g DW), Na+/K+ ratio (0.72 – 0.124), physical appearance (score 1 - 3), yellowing of leaves (1 - 3), shoot tip burning (1 - 3) and leaf curling (1 - 3) which were comparable to the salt tolerant parent CSR10. Molecular analysis of BAD2A aroma locus revealed an overall ratio of 14:75:11 for homozygous fragrant, heterozygous fragrant and non-fragrant plants, respectively, in Basmati x indica derived F2, F3, F4 and BC1F1 segregating populations. DNA fingerprint databases of 40 Pusa1121 x CSR10 F3 plants, 24 PB1460 x CSR10 F3, 10 Pusa1121 x CSR10 F4 plants and 21 Pusa1121 x CSR10 BC1F1 plants were prepared using 99, 94, 97 and 99 polymorphic SSR markers, respectively, and used for linkage mapping via composite interval mapping (WinQTL Cartographer 2.5). As many as 100 QTL were mapped for various salt stress tolerance attributes (shoot length, 29; root length, 9; Na+, 10; K+, 22 and K+/Na+ ratio, 30). Eleven QTL associated with K+/Na+ ratio had percent phenotypic variance more than 20% while 11 QTL had LOD score more than 7.5. Ten QTL (qK/Na7.1, qK/Na10.2, qK9.1, qK11.1, qK6.1, qK10.1, qK10.2, qK2.1, qK10.3 and qK/Na2.1) had LOD score more than 9.0 and eight (qK2.1, qK10.2, qRL2.1, qK6.1, qK10.1, qRL2.1, qSL3.1 and qK/Na2.1) were identified with r2 values more than 50. Maximum number (28) of QTL were mapped on chromosome 2 followed by chromosome 1 (15 QTL). Notably, qK/Na2.1 on chromosome 2 (map position, 12.8 cM) accounted for 83.0% phenotypic variance (DPE - Pusa1121); qNa2.1 at same map position also contributed for Na+ content with 49.3% phenotypic effect. A number of promising plants were selected based on screening in the net house and field evaluation for grain yield, yield components and L/B ratio. In 2016, twelve F4 plants of the two crosses were selected through screening in the net house having low Na+ content (<5.12 μmoles/g DW) and high K+ (>47.97 μmoles/g DW) and Na+/K+ ratio between 0.084 - 0.108. The selected plants were homozygous fragrant, heterozygous fragrant and non-fragrant in the ratio of 4:6:2 based on BAD2A locus analysis. The selected plants possessed 78 - 93 favorable alleles/QTL for salt tolerance attributes either in homozygous or heterozygous state. Field evaluation in 2016 Kharif season also led to the selection of 55 plants (25 Pusa1121 x CSR10 and 15 PB1460 x CSR10 F4; 15 Pusa1121 x CSR10 BC1F2) having grain yield and grain length/breadth ratio in the range of 7.7 - 27.5 g and 4.17 - 5.14. Selected plants can be further used in salt tolerance breeding programs in Basmati rice.
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