Asif B. Shikari

Marker-assisted introgression of three dominant blast resistance genes into an aromatic rice cultivar Mushk Budji

Modern high yielding rice varieties have replaced most of the traditional cultivars in recent past. Mushk Budji, is one such short grained landrace known for its aroma and exquisite quality, however, is highly susceptible to blast disease that has led to considerable decline in its area. Mushk Budji was crossed to a triple-gene donor line, DHMAS 70Q 164-1b and followed through marker-assisted foreground and background selection in first and second backcross generations that helped to incorporate blast resistance genes Pi54, Pi1 and Pita. Marker-assisted background selection was carried out using 78 SSR and STS markers that helped to reduce linkage drag around the genes Pi54, Pi1 and Pita to 2.74, 4.60 and 2.03 Mb, respectively. The three-gene lines in BC2F2:3 were genotyped using 50 K SNP chip and revealed more than 92% genome similarity to the RP. 2-D gel assay detected differentially expressing 171 protein spots among a set of backcross derived lines, of which 38 spots showing match score of 4 helped us to calculate the proteome recovery. MALDI-TOF analysis helped to detect four significant proteins that were linked to quality and disease resistance. The improved lines expressed resistance to blast under artificial and natural field conditions.

Molecular marker-based validation of blast resistance gene Pi54 and identification of potential donors in temperate high altitude rice (Oryza sativa L.)

More than 100 genes have been reported to impart resistance against rice blast, however, not all are equally effective. Their effectiveness relies on factors such as the diversity in pathogen races prevailing in a certain area, rate of pathogen evolution, genetic background of a host and few others. Pi54 is a major gene showing resistance to Magnaporthe populations in North-west Himalayas. In search of novel temperate donors suitable to high altitudes, a set of germplasm was screened using gene based markers for Pi54. Eighty three exotic and indigenous germplasm lines were genotyped using gene based markers and also validated for disease reaction using Pi54 gene specific isolate namely, Mo-nwi-kash-32. Nine out of 83 germplasm lines amplified resistance specific alleles with both the markers Pi54 MAS and Pikh-STS. All these lines expressed resistance against the said diagnostic isolate, thereby validating the possible presence of gene in the lines. Further validation using more number of isolates and sequence analysis will help in mining useful alleles for this gene.

Breeding value, parent offspring regression and trait association for agronomic and quality traits in rice (Oryza sativa L.)

To estimate breeding value, correlation and heritability in rice, two parental lines of rice, Mushk Budji and DHMAS 70Q 164-1b were crossed to generate F1 plant that was subsequently backcrossed to raise 29 BC1F1 plants. The best performing single BC1F1 plant was selected and selfed to raise BC1F2 population. The selected 14 BC1F2 plants were advanced to raise 104 BC1F2: 3 individuals. The observations were recorded on parents, BC1F1, BC1F2, BC1F2: 3 individuals for 13 agronomic and quality traits. The line SKUA-485 27–47 recorded high breeding values for all the traits. This line is expected to yield progenies having high grain yield and contributing traits. The parent offspring regression (rOP) is a direct measure of heritability in broad sense and was worked out using BC1F2 and BC1F2: 3 progenies and PH recorded high positive b-value of 0.75. The grain shape as measured by kernel length: breadth ratio showed high h2 (0.58). The highest correlation was recorded between traits grain yield and effective tillers per plant (r=0.760). Milled rice length recorded significant positive correlation with kernel length: breadth ratio and kernel length after cooking, while it showed negative but significant correlation with elongation ratio. Backcross generations particularly from genotype SKUA-485-27-47 were expected to recover progenies with more number of effective tillers per plant, high grain yield and short bold grain type.