Interspecific hybridization for the development of chromosome segment substitution lines of rice in India

Abstract

Chromosome segment substitution lines (CSSLs) are useful genetic stocks for precise mapping of quantitative trait loci (QTLs) and the evaluation of gene action or interaction in inter-specific crosses. As part of National
Professor Project at Indian Institute of Rice Research (IIRR), seven popular high yielding Indian rice varieties of different durations were selected as recurrent parents and three wild accessions O. nivara IC 336681(27), O.
nivara IC 283150(29) and O. rufipogon IC 309814(18) with high photosynthetic use efficiency as donor parents for development of CSSLs. Parental accessions were genotyped along with japonica, aus type and aromatic genotypes as reference. The genotypes grouped into four populations based on diversity analysis and population structure. A set of 400 core set SSRs distributed throughout rice genome were used to identify 70-100 polymorphic markers for genotyping each back cross generation. The germination of F1 hybrid seeds
varied from 60% (Krishnahamsa x O. nivara (29)) to 100% (Varadhan x O. nivara (29)). The average seed set was 38.9% in O. nivara (27), 26% in O. nivara (29) and 30.1% in O. rufipogon (18) crosses. True F1 plants were
confirmed using polymorphic SSRs RM1, RM5, RM9 and RM16. Only 15% F1 were true hybrids in crosses using O. nivara (27), 7% with O. nivara (29) and 21% with O. rufipogon (18) accessions. The F1 hybrids were
characterized for plant height, number of tillers, panicle number, panicle length and stem colour. All F1 hybrids were fertile. Since F1 of crosses involving Cottondora Sannalu (MTU1010), Swarna (MTU7029) and Dhanarasi
(DRRDhan31) with O. rufipogon showed high vigour for plant height, tiller and panicle number, the first two were selected for CSSL development. F1 hybrids were backcrossed with respective recurrent parent to obtain BC1 to BC4 plants. Inter-specific hybridization followed by backcrossing offers a great potential for developing rice lines with significant increase in several desirable agronomical traits. The marker characterized CSSLs of MTU1010 and Swarna will be a good genetic resource for fine mapping, gene discovery and rice improvement.