Understanding the Inconsistent Nature of Blast Resistance in Combined Bacterial Leaf Blight and Blast Gene Pyramided Lines of Rice Variety Tellahamsa

Abstract Background Rice blast and bacterial leaf blight (BLB) are the most limiting factors for rice production in the world which cause yield losses typically ranging from 20 to 30% and can be as high as 50% in some areas of Asia especially India under severe infection conditions. Methods and Results An improved line of Tellahamsa TH-625-491 having two BLB resistance genes (xa13 and Xa21) and two blast resistance genes (Pi54 and Pi1) with 95% Tellahamsa genome was used in the present study. TH-625-491 was validated for all four target genes and was used for backcrossing with Tellahamsa. Seventeen IBC1F1 plants heterozygous for all four target genes, 19 IBC1F2 plants homozygous for four, three and two gene combinations and 19 IBC1F2:3 plants also homozygous for four, three and two gene combinations were observed. Among seventeen IBC1F1 plants IBC1F1-62 plant recorded highest recurrent parent genome (97.5%) covering 75 polymorphic markers. A total of 920 IBC1F2 plants were screened and 19 homozygous plants possessing four, three and two target genes along with bacterial blight resistance. Background analysis was done in all 19 homozygous IBC1F2 plants possessing BLB resistance (possessing xa13, Xa21, Pi54 and Pi1 in different combinations) with five parental polymorphic SSR markers. IBC1F2-62-515 recovered 98.5% recurrent parent genome. The four, three and two gene pyramided lines of Tellahamsa exhibited inconsistent resistance to blast. Conclusions Thus, there is a dire need for studying the blast pathogen because it is having complicated developmental processes in association with surrounding environments as strategies for survival and dispersal.