Marker assisted and doubled haploidy breeding for the development of blast and bacterial blight resistant rice pyramid lines

Abstract

newline Rice (Oryza sativa L.) serves as a major carbohydrate source for nearly half of the world s population and provides livelihood to the people of Asia. Rice blast caused by Magnaporthe grisea and bacterial leaf blight caused by Xanthomonas oryzae pv.oryzaeare the two major diseases affecting rice productivity in north-western Himalayan region of India. Biotechnological tools like anther culture and molecular marker technology hold a great role as a catalyst in accelerating the pace of blast and bacterial blight resistance breeding. In order to pyramid 2 blast (Pi9 and Pita) and 2 bacterial blight (Xa21 and Xa38) resistance genes in a popular rice variety HPR2143 , foreground selection was done to identify single gene positive BC2F2 homozygous progenies of 4 crosses, viz. HPR2143/PB1 (Pi9), HPR2143/DHMAS164 (Pita), HPR2143/IRBB54 (Xa21) and HPR 2143/PR114 (Xa38) using gene derived markers. The foreground selection resulted in identification of 5 plants homozygous for the gene Pita, 20 for Pi9, 12 for Xa21 and 6 for Xa38.In order to pyramid two genes each against rice blast, progenies positive for gene Pita were crossed reciprocally with progenies positive for the gene, Pi9. Likewise, the homozygous positive plants for genes, Xa21 and Xa38 were crossed reciprocally to produce F1s. Overall crossability among the selected derivatives over both cross combinations (Pita × Pi9) and (Xa21 × Xa38) was recorded to be 38.61%. Anther culture of developed F1s was attempted for fixation of genes. For cross (Pita + Pi9 and reciprocals), overall callus induction and regeneration frequency of 9.2% and 6.5%, respectively was recorded. The frequency of green plantlet regeneration recorded was 29.9% thereby resulting in an overall anther culture efficiency of 0.18% from a total of 22562 anthers cultured. For cross 2 (Xa21× Xa38 and reciprocals), observed callus induction and regeneration frequency was 9.08% and 5.7%, respectively. A total of 88 regenerating calli resulted in regeneration of 20 green (22.7%) and 68 albino plants (77.2%) with an overall anther culture efficiency of 0.11% in a total of 16894 cultured anthers. Out of 57 plants, 28 were positive for the gene combination, Pita + Pi9 and 15 for Xa21 + Xa28. Field evaluation of 38 generated doubled haploid pyramid (DHP) lines having sufficient seeds revealed presence of significant variation among the lines for all nine traits studied. Based on their performance, promising DHP lines for different economic traits were identified including three best DHP lines, i.e. DHP57, DHP4 and DHP16 performing close to the check, HPR2143 for seed yield/plant. The material generated can be used directly for identification of variety(ies) as well as can further be used as genetic stocks in the future breeding programmes for developing broad spectrum and durable multiple disease resistance against rice blast and bacterial leaf blight diseases.