Methylglyoxal detoxification pathway in barley genotypes after infection with Bipolaris sorokiniana

The present investigation was carried out to study the leaf composition and methylglyoxal pathway in four barley genotypes on infection with Bipolaris sorokiniana. PL 891 was found to be highly resistant, followed by PL 807 as a resistant cultivar, while PL 426 and RD 2786 depicted susceptible behavior to spot blotch disease. Total soluble sugars increased by more than 1.4 folds in resistant genotypes at the growth stage (GS) 55 (half inflorescence emerged) while declined in the sensitive ones. However, control leaves of the latter had more total soluble sugars and cholorophyll contents at GS 55 but declined after infection. Glyoxalase I activity increased in the lower leaves of PL 807, PL 891 and PL 426 on infection with Bipolaris sorokiniana at GS 87 (hard dough). Glyoxalase II activity increased in the infected leaves of PL 891, PL 807, and PL 426 by 1.3, 1.1 and 1.4 folds respectively at GS 55 stage while declined by more than 1.3 folds in the susceptible genotype RD 2786. Glyoxalase III activity increased in the flag and lower leaves of PL 807 at both stages while declined or remained unaffected in other genotypes indicating the action of glutathione independent pathway in this genotype. Methylglyoxal reductase activity increased by more than 1.3 and 1.9 folds respectively in the flag and lower leaves of both the resistant genotypes. Negative correlation of MG with Gly I (-0.431**) and with methylglyoxal reductase (-0.274*) verified the role of these enzymes in its detoxification in response to leaf blight disease. Analysis of the data shows that the rise in total soluble sugars at initial stages and the activities of Gly III and methylglyoxal reductase at later stages along with the maintenance of redox pool could be responsible for the resistant nature of PL 891 and PL 807.