Marker assisted selection of transgressive segregants in rice carrying favourable alleles for P-deficiency and submergence tolerance under acidic low land soils
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Date
2017-04
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College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam
Abstract
Rice (Oryza sativa L., 2n= 2x= 24) is affected by several biotic and abiotic stresses (constraints) in North-Eastern region of India. More than 95% area in the North Eastern Hill Region is affected by soil acidity and frequently prone to flash floods. P deficiency and submergence are therefore, two of the most prevalent stresses in the region. As markers and donors for tolerance to these stresses have been identified, they were used in the present study to generate and select transgressive segregants carrying desired alleles for traits of interest. Four biparental crosses (Shasarang x Kasaltah, Shasarang x Samba mashuri-sub1, Lal jangli x Sahbhagi Dhan, Lal jangli x Priya) were established. Generated F2 populations were evaluated under lowland acidic soils during 2014 and total of 52 transgressive segregants from four F2 populations were selected, harvested individually and carried forwarded to F3 generation, along with Single Seed Descent (SSD) from each F2 population. The 52 F3 families along with SSD progenies were evaluated in Kharif, 2015 for different agronomic traits to obtain response to selection and heritability estimates. Simultaneously, in each generation, phenotypically selected lines were subjected to marker assisted selection for Sub1 and Pup1 loci in respective progenies. The F3 progeny showed significant positive regression on their selected F2 parents for grain yield, plant height, Panicles length and harvest index indicating the effectiveness of selection for these traits in early segregating generation. But, with respect to days to 50% flowering, Tiller no. at 30 days, tiller no. at 60 days, panicle number, spikelet fertility, biological yield and test weight, non-significant regression in F3 generation was observed. This Indicated the direct selection for these characters during early generation (F2) may not be effective. Significant response to selection for grain yield was observed for all the crosses, ranging from 22 to 35 per cent over F2 mean. Four selected F3 families of the cross Shasarang x Samba mashuri-sub1 viz. ULRC 29-1 and ULRC 29-15, ULRC29-115 and ULRC-170 were found to be homozygous for submergence tolerance. In case of the cross Shasarang x Kasaltah, F3 families ULRC24-30 and ULRC 24-48 were identified as carrying both, K46-1 and K46-2, while ULRC24-4 family was positive for K46-2 and PR1-2 for tolerant Pup1 alleles. Seedlings of selected F4 families were subjected to submergence and hydroponic screening (under P deficient condition) for trait validation. Under hydroponics ULRC 24-99-1 was found to be performing consistently for shoot length, root length, fresh shoot weight and fresh root weight under both control and treatment conditions. Lines ULRC 24-99-1, ULRC 33-57-1 showed higher amount of P uptake in association with phosphorous use efficiency (PUE) under P deficient conditions. On the other hand, majority of the lines selected from cross Shasarang x Samba mashuri-sub1 showed equal level of tolerance to the donor for submergence tolerance. The study highlights the feasibility, importance and effectiveness of MAS in early segregating generations, which led to identification of transgressive progenies with desired genotypic and phenotypic constitution. These lines, once stable may be tested at multiple locations can be released directly as variety to enhance the productivity in the NEH region and can also serve as potential donors in future breeding programs aimed at developing improved cultivars with desirable agronomic traits in acidic lowland rice ecosystems.
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Keywords
Rice, Marker assisted selection