Biochemical basis of defense response in pigeonpea against maruca vitrata (fabricius) infestation
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Date
2022
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Punjab Agricultural University
Abstract
The present investigation was carried out to identify the biochemical basis of Maruca vitrata (pod borer) infestation in pigeonpea. Two pigeonpea genotypes, AL 1747 (moderately resistant) and MN 1 (susceptible) were compared for methylglyoxal detoxification, proline metabolizing enzymes along with free radical scavenging activities in leaves, flowers and pods under control and infested conditions. Lower accumulation of methylglyoxal (MG) in AL 1747 genotype was due to higher activities of enzymes of glyoxylase (Glyoxylase I, Glyoxylase II, Glyoxylase III) and non-glyoxylase (methylglyoxal reductase, MGR) pathway that converts MG into lactate. Higher activity of lactate dehydrogenase (LDH) in AL 1747 indicates the utilization of end product of MG detoxification pathway for energy production. Higher glutathione content in AL 1747 genotype might be responsible for efficient working of MG detoxification pathway under insect infestation. Higher activity of γGCS
in AL 1747 genotype maintains the glutathione pool, necessary for the proper functioning of glyoxylase pathway to carry out the detoxification of methylglyoxal, thereby enhancing resistance. Higher activities of GST and GPX in AL 1747 genotype might be responsible for detoxification of toxic products that accumulates upon insect infestation. However, decreased activities of glyoxylase enzymes and MGR in MN 1 resulted in accumulation of MG which limits plant growth and development. The reciprocal regulation of proline dehydrogenase (ProDH) with proline biosynthesizing enzymes such as ornithine aminotransferase (OAT), glutamate dehydrogenase (GDH), Δ1-pyrroline-5-carboxylate synthetase (P5CS) in AL 1747 suggests that proline accumulation was initiated as part of induced defense response against M. vitrata infestation. Higher free radical scavenging activities such as 2,2-diphenyl-1-picryl hydrazyl (DPPH), superoxide anion, hydroxyl ion, nitric oxide, Ferric reducing antioxidant power (FRAP) might be responsible for lowering ROS accumulation upon insect infestation. Hence, the resistance of AL 1747 to M. vitrata might be due to higher activities of enzymes of glyoxylase and non-glyoxylase system; proline metabolizing enzymes as well as free radical scavenging activities thereby mitigating insect infestation induced oxidative stress.
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Sukhmanpreet Kaur (2022). Biochemical basis of defense response in pigeonpea against maruca vitrata (fabricius) infestation (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.