Abstract
The present study evaluated the defense response of Chickpea wilt resistant and susceptible cultivars inoculated with pathogen Fusarium oxyporum f.sp. ciceri (Foc). Evaluation of pre-induced and pathogen-induced defense at 7 (S1), 15 (S2) and 30 (S3) days showed that the enzymatic activities differed not only within the root, stem and leaves but also between susceptible and resistant cultivars of chickpea and increased after inoculation with Foc. Peroxidase (PO) activity increased in all the tissues from S1 to S2 and declined thereafter. Conspicuous changes occurred at the rate of increase in activity of the enzyme between resistant and susceptible cultivars upon Foc inoculation over their corresponding control at the S2. Polyphenol oxidase (PPO) activity in resistant cultivars increased by 30% with over uninoculated control and induction was up to S3. The level of enzyme activity diminished from S2 to S3 and even fell below control levels in susceptible cultivars. Catalase (CAT) activity followed peroxidase trend however it was induced at S1 in Foc inoculated and at S2 in un-inoculated plants. Increase in CAT induction was significant in leaf tissues of infected plants and continued up to S3. Phenylalanine ammonia lyase (PAL) activity increased from S1 to S2 and thereafter it either slightly decreased or remained unchanged at S3. Foc inoculation elicited a sharp increase in PAL activity in the leaf and stem tissue of resistant cultivars. Foc inoculated induced β-1,3-glucanase and chitinase activity in the test cultivars. Maximum induction of chitinase was observed at S2 in roots of resistant cultivars whereas un-inoculated plants showed much less conspicuous changes. β-1,3-glucanase activity was high in stem tissues. Both control and challenged plants had higher levels of β-1,3-glucanase activity at S2 and S3, but the proportionate increase was much higher in resistant cultivars. The expression pattern of these defense enzymes reveals their use as established resistance markers and provides scope for manipulating their expression and development of wilt-resistant transgenic chickpea.
Highlights
Chickpea (Cicer arietinum L.) is a self-pollinated diploid (2n=2x=16 with genome size of 738 Mb) leguminous crop, cultivated mainly in semiarid environments of the world and ranks second in area and third in production among the pulses worldwide
Defense-related enzymes constitute an important protective system for plants against pathogen invasion such as phenylalanine ammonia-lyase (PAL) is the primary enzyme in phenylpropanoid metabolism and plays an important role in the synthesis of several defense-related secondary compounds known as phytoalexins (Tahsili et al, 2014)
Since information on pre-induced and induced biochemical mechanisms of resistance are pre-requisite for better understanding of the pathogens-host interaction and provide basis for better management of disease, the present investigations were carried as an attempt to analyse and correlate the biochemical basis of disease resistance, by measuring levels of peroxidise, catalase, polyphenol oxidase (PPO), J Microbiol Biotech Food Sci / Datta and Lal 2018 : 7 (4) 426-431
Summary
Chickpea (Cicer arietinum L.) is a self-pollinated diploid (2n=2x=16 with genome size of 738 Mb) leguminous crop, cultivated mainly in semiarid environments of the world and ranks second in area and third in production among the pulses worldwide. Plants activate a large array of defence mechanisms in response to pathogen attack and host-pathogen cross-talk. A crucial factor determining the success of these mechanisms is the speed of their activation which needs thorough understanding of how host plants recognize pathogen attack and control expression of defence mechanisms. The hypersensitive response of plants is accompanied by the synthesis of number of host proteins thought to be involved in defence mechanisms. Researches on elucidation of host defensive responses to pathogen invasion have determined catalase, superoxide dismutase (SOD), peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL) and "pathogenesis related" (PR) proteins viz. Giri et al (1998) observed the differential induction of chitinase activity in susceptible and resistant cultivars of chickpea and decrease in β-1,3-glucanase in the resistant cultivars in response to the pathogen infection. Since information on pre-induced and induced biochemical mechanisms of resistance are pre-requisite for better understanding of the pathogens-host interaction and provide basis for better management of disease, the present investigations were carried as an attempt to analyse and correlate the biochemical basis of disease resistance, by measuring levels of peroxidise, catalase, PPO,
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