M. Nagarajan

Molecular breeding for the development of multiple disease resistance in Basmati rice

Marker assisted backcross breeding for combining three resistance genes (xa13 and Xa21 for Bacterial Blight, Pi54 for blast) and a major QTL (qSBR11-1 for resistance to Sheath blight) in Basmati rice.

Marker-aided Incorporation of Xa38 , a Novel Bacterial Blight Resistance Gene, in PB1121 and Comparison of its Resistance Spectrum with xa13 + Xa21

Basmati rice is preferred internationally because of its appealing taste, mouth feel and aroma. Pusa Basmati 1121 (PB1121) is a widely grown variety known for its excellent grain and cooking quality in the international and domestic market. It contributes approximately USD 3 billion to India’s forex earning annually by being the most traded variety. However, PB1121 is highly susceptible to bacterial blight (BB) disease. A novel BB resistance gene Xa38 was incorporated in PB1121 from donor parent PR114-Xa38 using a modified marker-assisted backcross breeding (MABB) scheme. Phenotypic selection prior to background selection was instrumental in identifying the novel recombinants with maximum recovery of recurrent parent phenome. The strategy was effective in delimiting the linkage drag to <0.5 mb upstream and <1.9 mb downstream of Xa38 with recurrent parent genome recovery upto 96.9% in the developed NILs. The NILs of PB1121 carrying Xa38 were compared with PB1121 NILs carrying xa13 + Xa21 (developed earlier in our lab) for their resistance to BB. Both NILs showed resistance against the Xoo races 1, 2, 3 and 6. Additionally, Xa38 also resisted Xoo race 5 to which xa13 + Xa21 was susceptible. The PB1121 NILs carrying Xa38 gene will provide effective control of BB in the Basmati growing region.

Marker assisted pyramiding of major blast resistance genes Pi9 and Pita in the genetic background of an elite Basmati rice variety, Pusa Basmati 1

Basmati is a premium quality rice of India which is highly priced in the international market. Pusa Basmati 1, an elite Basmati rice variety is highly susceptible to rice blast caused by Magnaporthe oryzae. Therefore, pyramiding blast resistance genes is essential to effectively combat the blast disease and increase the durability of resistance genes. The blast resistance genes Pi9 and Pita have been earlier demonstrated to be effective in Basmati growing regions of the country. Therefore, in the present study, monogenicnear isogenic lines Pusa 1637-18-7-6-20 and Pusa 1633-3-88-16-1 carrying Pi9 and Pita, respectively, were intercrossed to generate pyramided lines through marker assisted foreground, background and phenotypic selection for recurrent parent phenotype. The pyramided lines carrying Pi9+Pita were found to be either at par or superior to the recurrent parent Pusa Basmati 1 for agro-morphological, grain and cooking quality traits. Further, these pyramided lines were also found to show resistance against three virulent pathotypes of M. oryzae namely, Mo-nwi-kash 1, Mo-nwi-lon2 and Mo-ei-ran1, when evaluated under artificial inoculation conditions as well as in the natural epiphytotic conditions of uniform blast nursery at two locations. The developed pyramided lines are the potential sources of blast resistance genes in the Basmati improvement program and can also be released for commercial cultivation after required testing.

Development of Basmati rice genotypes with resistance to both bacterial blight and blast diseases using marker assisted restricted backcross breeding

Marker assisted backcross breeding (MABB) is aimed at introgression of trait(s) into a popular variety to augment specific trait(s) in an otherwise popular variety. While MABB can improve a variety with respect to introgressed trait(s), it offers very little scope for improvement of other traits. Marker assisted restricted backcross breeding (MARBB) is an alternative which can help in identifying transgressive segregants especially, when the donor parent is an elite genotype with several desirable traits. In the present study, restricted backcrossing followed by pedigree selection was used for the development of improved genotypes of Basmati rice with BB and blast diseases using an early maturing Basmati rice variety, Pusa Basmati 1509 as recurrent parent and an elite restorer line, Pusa 1790 as donor. Foreground selection for xa13, Xa21, Pi2 and Pi54 in the backcross progenies was combined with phenotypic selection for agronomic and grain quality traits to ensure premium Basmati grain quality in the progenies. Multilocation yield trial was conducted to evaluate the performance of the improved Basmati rice genotypes with both BB and blast resistance. Pusa 1847-12-62-115-20-6 and Pusa 1847-12-62-190-39-7 recorded significantly higher yields of 68.88 and 62.44 q/ha, respectively, compared to PB 1509 (57.88 q/ha). The improved progenies exhibited resistance to BB with an average lesion length of 2 cm, and blast with scores between 0–2, while PB 1509 was highly susceptible. Another genotype, Pusa 1847-12-62-37-8-3 exhibited head rice recovery (HRR) of 63.99%, which was significantly higher than in PB 1509 (56.40%). Marker assisted selection was also effected for fertility restoration genes and improved grain quality traits based on which two improved Basmati rice genotypes pyramided with BB and blast resistance namely, Pusa 1847-12-62-115-20-6 and Pusa 1847-12-62-190-39-7 were found promising, along with improved grain and cooking quality as well as restoration potential, which could be used in breeding better quality hybrids.