Jain, JyotiVashisth, Tanvi2023-12-112023-12-112022Vashisth, Tanvi (2022). Characterization of blast and bacterial blight resistance genes in basmati rice (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810202583The present study was conducted to evaluate MCF1 populations of basmati rice developed from complex crosses (designated as cross A and cross B). Phenotypic evaluation of cross A was done for resistance to neck blast (Pyricularia oryzae) using highly virulent isolate NB-7 under artificial inoculation conditions. Cross B was evaluated against neck blast (NB-7) as well as bacterial blight (Xanthomonas oryzae pv. oryzae) using two pathotypes PbXo-7 and PbXo-8 under artificial inoculation conditions. Among the MCF1 population comprising of 421 plants from cross A, 12 plants were immune, 6 were highly resistant, 30 were resistant and 59 were moderately resistant to neck blast isolate NB-7. A population of 103 plants from cross B showed immune response to neck blast in 9 plants, while 12 plants were resistant to pathotype PbXo-7 and 27 plants were resistant to PbXo-8. Both the crosses were also analyzed for known blast resistance genes (Pi54, Pi2, Pi9 and Pi68) and bacterial blight resistance genes (xa13 and Xa21). A total of 200 plants were tested in cross A, and 199 were found to have the Pi54 gene, while 155 had the Pi2 gene. Only 4 plants showed the presence of Pi9 gene in cross A. The combination of two blast resistance genes was found in 149 plants (Pi54 + Pi2) and in four plants there was a combination of three genes (Pi2 + Pi54 + Pi9). In the cross B, only two plants showed the presence of blast resistance gene (Pi9) and 40 plants showed the presence of Xa4 gene. Two plants were heterozygous for bacterial blight resistance gene (xa13) and four were heterozygous for Xa21. There were only two plants identified as having blast + BB resistance genes (Pi9+Xa4) and one plant showing two BB resistance genes (Xa21+Xa4). The assay of biochemical parameters indicated a significant increase in activity of peroxidase, PPO, PAL, catalase and hydrogen peroxide among resistant/moderately resistant genotypes as compared to the susceptible genotypes at 10 days after inoculation with P. oryzae. Out of 35 genotypes screened against leaf and neck blast phases under artificial inoculation conditions, none was found to be resistant to both the phases. Only two entries viz., Tetep and Pusa Basmati 1637 showed moderately resistant reaction to both neck and leaf blast with susceptibility index (Sx) value <3. Three genotype namely JJ92, UPR3519-18-1-1 and IET 15392 exhibited moderately resistant reaction to leaf blast but were moderately susceptible to neck blast under artificial inoculation conditions. Under natural epiphytotic conditions (hotspot location), five entries namely JJ92, UPR3519-18-1-1, IET 15392, Tetep and Pusa Basmati 1637 showed moderately resistant reaction to neck blast and resistant reaction to leaf blast. The current study has the potential to contribute towards strengthening ongoing blast and bacterial blight resistance breeding program by utilizing the identified donors harbouring single as well as multiple resistance genes to both the diseases.EnglishThesis