Abstract
Two popular stable restorer lines, CB 87 R and CB 174 R, were improved for blast resistance through marker-assisted back-cross breeding (MABB). The hybrid rice development program in South India extensively depends on these two restorer lines. However, these restorer lines are highly susceptible to blast disease. To improve the restorer lines for resistance against blasts, we introgressed the broad-spectrum dominant gene Pi54 into these elite restorer lines through two independent crosses. Foreground selection for Pi54 was done by using gene-specific functional marker, Pi54 MAS, at each back-cross generation. Back-crossing was continued until BC3 and background analysis with seventy polymorphic SSRs covering all the twelve chromosomes to recover the maximum recurrent parent genome was done. At BC3F2, closely linked gene-specific/SSR markers, DRRM-RF3-10, DRCG-RF4-8, and RM 6100, were used for the identification of fertility restoration genes, Rf3 and Rf4, along with target gene (Pi54), respectively, in the segregating population. Subsequently, at BC3F3, plants, homozygous for the Pi54 and fertility restorer genes (Rf3 and Rf4), were evaluated for blast disease resistance under uniform blast nursery (UBN) and pollen fertility status. Stringent phenotypic selection resulted in the identification of nine near-isogenic lines in CB 87 R × B 95 and thirteen in CB 174 R × B 95 as the promising restorer lines possessing blast disease resistance along with restoration ability. The improved lines also showed significant improvement in agronomic traits compared to the recurrent parents. The improved restorer lines developed through the present study are now being utilized in our hybrid development program.
Highlights
The major goal of rice production is to fulfill the demand for the growing population and improve food security
The F1 plants in two crosses were confirmed for their heterozygous nature using the functional marker, Pi54 MAS
The present study was carried out with the objective to introgress a blast resistant gene, Pi54, into the background of popular restorer lines, CB 87 R and CB 174 R, through marker-assisted back-cross breeding coupled with screening for improved agronomic traits
Summary
The major goal of rice production is to fulfill the demand for the growing population and improve food security. Among various genetic approaches available today, hybrid rice technology is the most promising and accepted strategy for improving the rice productivity [1]. The hybrid rice production system suffers from various biotic stresses including fungal and bacterial diseases [1,2]. Fungal blast (Magnaporthe oryzae), caused by an ascomycete fungus, is one of the major biotic diseases of rice contributing to yield loss up to 10–30% globally [3,4,5,6,7]. In India the disease, under severe and favorable conditions, can cause yield losses ranging from 74 to 100% [8,9,10].
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