Browsing by Author "Lokesh, Veeresh"

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Greenhouse and field experiments revealed that clove oil can effectively reduce bacterial blight and increase yield in pomegranate
(John Wiley & Sons, 2021) Kumar, Pavan; Lokesh, Veeresh; Doddaraju, Pushpa; Kumari, Aprajita; Singh, Pooja; Meti, Bharati S.; Sharma, Jyotsana; Gupta, Kapuganti Jagadis; Manjunatha, Girigowda
Bacterial blight in pomegranate is a devastating disease caused by bacterial pathogen Xanthomonas axonopodis pv. punicae (XAP), recording huge damage to pomegranate crop worldwide. Antibiotics and copper-based chemicals are being used for the management of this blight, while in this present work, we investigated the effect of eugenol and clove oil either singly or in combination with copper oxychloride (COC) on the induction of plant defense responses and concomitant prevention of bacterial blight. Our results provided evidence that clove oil (0.2%–1%) and eugenol (0.1% and 0.2%) successfully inhibit the growth of XAP in paper disk diffusion assay. Strikingly under the greenhouse condition, clove oil (0.2%) as foliar application 24 h before XAP inoculation recorded the lowest disease severity of 7.34%, whereas eugenol (0.2%) recorded maximum disease severity of 14.56%. However, the combination of clove oil (0.2%) and copper oxychloride (0.3%) recorded the least disease severity of 2.38%. A similar trend was observed in field conditions. Prophylactic application of clove oil leads to enhanced nitrate reductase activity and nitric oxide production which was further enhanced in clove oil pre-treated plants challenged with XAP. Strikingly, the total ROS and H2O2 levels were reduced in response to clove oil application. Clove oil also induced the systemic response by inducing expression levels of defense genes. The reduction of disease severity by clove oil and COC combination also reflected on total yield recording via large-scale field experiments where maximum yield of 14.04 tonnes/acre was observed, whereas streptocycline application recorded 11.12 tonnes/acre. Application of COC and clove oil resulted in a high remunerative value of ₹ 1:5.6, compared to streptocycline (1:4.85) and control (1:1.85). The present study revealed that clove oil as a plant derivative and eugenol as a synthetic option can be effectively used for the successful management of bacterial blight in pomegranate.
Polyamine induction in postharvest banana fruits in response to NO donor SNP occurs via L-arginine mediated pathway and not via competitive diversion of S-adenosyl-L-methionine
(MDPI AG, 2019) Lokesh, Veeresh; Manjunatha, Girigowda; Hegde, Namratha S.; Bulle, Mallesham; Puthusseri, Bijesh; Gupta, Kapuganti Jagadis; Neelwarne, Bhagyalakshmi
Nitric oxide (NO) is known to antagonize ethylene by various mechanisms; one of such mechanisms is reducing ethylene levels by competitive action on S-adenosyl-L-methionine (SAM)—a common precursor for both ethylene and polyamines (PAs) biosynthesis. In order to investigate whether this mechanism of SAM pool diversion by NO occur towards PAs biosynthesis in banana, we studied the effect of NO on alterations in the levels of PAs, which in turn modulate ethylene levels during ripening. In response to NO donor sodium nitroprusside (SNP) treatment, all three major PAs viz. putrescine, spermidine and spermine were induced in control as well as ethylene pre-treated banana fruits. However, the gene expression studies in two popular banana varieties of diverse genomes, Nanjanagudu rasabale (NR; AAB genome) and Cavendish (CAV; AAA genome) revealed the downregulation of SAM decarboxylase, an intermediate gene involved in ethylene and PA pathway after the fifth day of NO donor SNP treatment, suggesting that ethylene and PA pathways do not compete for SAM. Interestingly, arginine decarboxylase belonging to arginine-mediated route of PA biosynthesis was upregulated several folds in response to the SNP treatment. These observations revealed that NO induces PAs via l-arginine-mediated route and not via diversion of SAM pool.