Abstract
Bacterial blight (BB) disease and submergence due to flash flood are the two major constraints for achieving higher yield from rainfed lowland rice. Marker-assisted backcross breeding was followed to develop submergence tolerant and durable BB resistant variety in the background of popular cultivar ‘Swarna’. Four BB resistance genes viz., Xa4, xa5, xa13, Xa21 and Sub1 QTL for submergence tolerance were incorporated into the mega variety. Foreground selection for the five target genes was performed using closely linked markers and tracked in each backcross generations. Background selection in plants carrying the target genes was performed by using 100 simple sequence repeat markers. Amongst backcross derivatives, the plant carrying five target genes and maximum recurrent parent genome content was selected in each generation and hybridized with recipient parent. Eighteen BC3F2 plants were obtained by selfing the selected BC3F1 line. Amongst the pyramided lines, 3 lines were homozygous for all the target genes. Bioassay of the 18 pyramided lines containing BB resistance genes was conducted against different Xoo strains conferred very high levels of resistance to the predominant isolates. The pyramided lines also exhibited submergence tolerance for 14 days. The pyramided lines were similar to the recurrent parent in 14 morpho-quality traits.
Highlights
IntroductionThe queen of cereals is life for millions of global population. Rice grain is a source of carbohydrate, protein, specific oils, dietary fibre, vitamins, many minerals and other disease-fighting phyto-compounds for which, known as golden cereal
Rice, the queen of cereals is life for millions of global population
Linked DNA markers have been used for several Bacterial blight (BB) resistance genes that are widely used in marker-assisted selection[4,5,6,27,28,29,30,31,32,33,34,35,36,37]
Summary
The queen of cereals is life for millions of global population. Rice grain is a source of carbohydrate, protein, specific oils, dietary fibre, vitamins, many minerals and other disease-fighting phyto-compounds for which, known as golden cereal. Rice is cultivated in 163.2 million hectares of which approximately 45% area is under rainfed ecology with low productivity due to various abiotic and biotic stresses[1]. Improved varieties are essentially needed that combine high grain yield with submergence tolerance along with in-built resistance to major diseases and insect pests. Gene based markers for locating this major QTL are known for marker-assisted selection This QTL has been successfully incorporated into many popular high yielding submergence susceptible varieties through marker-assisted backcrossing (MAB)[8,17,24,25]. We report the successful gene stacking of four BB resistance genes, Xa4, xa[5], xa and Xa21 and Sub[1] for submergence tolerance through marker-assisted selection (MAS) in the mega variety ‘Swarna’
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