Browsing by Author "Kumar, R."

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Burkholderia gladioli strain NGJ1 deploys a prophage tail-like protein to feed on fungi
(American Phytopathological Society, 2019) Swain, D.M.; Yadav, S.; Tyagi, I.; Kumar, R.; Kumar, R.; Ghosh, S.; Das, J.; Jha, Gopaljee
Fungal pathogens are responsible for approximately two third of the infectious plant diseases. Due to extensive usages, pathogens have evolved resistance against most of the commonly used fungicides. Rice sheath blight disease caused by Rhizoctonia solani remains a serious threat to global sustainable agriculture. The pathogen has a complex biology and has been reported occurring world-wide causing necrosis and dampingoff on numerous host plant species. The pathogen is polymorphic and despite extensive efforts, till today no source of complete disease resistance has been identified against this pathogen. We have recently discovered a novel bacterium Burkholderia gladioli strain NGJ1 which has broad spectrum mycophagus ability. We also demonstrated that the bacteria NGJ1 deploys a prophage tail like protein (Bg_9562) to feed over fungi in a T3SS dependant manner. Moreover we observed that Bg_9562 protein has a broad spectrum antifungal activity on Rhizoctonia solani as well as several other phytopathogenic fungi. Furthermore, being equipped to kill and feed upon fungi, the mycophagous bacteria can serve as an experimental tool box to facilitate discovery of novel anti-fungal molecules. This opens up a new biotechnological application of this prophage tail like protein in controlling fungal diseases in rice as well as in other plants.
An innovative root inoculation method to study Ralstonia solanacearum pathogenicity in tomato seedlings
(American Phytopathological Society, 2018) Singh, N.; Phukan, T.; Sharma, P.L.; Kabyashree, K.; Barman, A.; Kumar, R.; Sonti, Ramesh V.; Genin, S.; Ray, S.K.
In this study, we report Ralstonia solanacearum pathogenicity in the early stages of tomato seedlings by an innovative root inoculation method. Pathogenicity assays were performed under gnotobiotic conditions in microfuge tubes by employing only 6- to 7-day-old tomato seedlings for root inoculation. Tomato seedlings inoculated by this method exhibited the wilted symptom within 48 h and the virulence assay can be completed in 2 weeks. Colonization of the wilted seedlings by R. solanacearum was confirmed by using gus staining as well as fluorescence microscopy. Using this method, mutants in different virulence genes such as hrpB, phcA, and pilT could be clearly distinguished from wild-type R. solanacearum. The method described here is economic in terms of space, labor, and cost as well as the required quantity of bacterial inoculum. Thus, the newly developed assay is an easy and useful approach for investigating virulence functions of the pathogen at the seedling stage of hosts, and infection under these conditions appears to require pathogenicity mechanisms used by the pathogen for infection of adult plants.
Ralstonia solanacearum virulence in tomato seedlings inoculated by leaf clipping
(John Wiley & Sons, 2017) Kumar, R.; Barman, A.; Phukan, T.; Kabyashree, K.; Singh, N.; Jha, Gopaljee; Sonti, R.V.; Genin, S.; Ray, R.K.
Ralstonia solanacearum is a phytopathogenic bacterium that colonizes the xylem vessels of host plants leading to a lethal wilt disease. Although several studies have investigated the virulence of R. solanacearum on adult host plants, infection studies of this pathogen on the seedling stages of hosts are less common. In a preliminary observation, inoculation of R. solanacearum F1C1 on 6- to 7-day-old tomato seedlings by a simple leaf-clip strategy resulted in a lethal pathogenic condition in seedlings that eventually killed these seedlings within a week post-inoculation. This prompted testing of the effect of this inoculation technique in seedlings from different cultivars of tomato and similar results were obtained. Colonization and spread of the bacteria throughout the infected seedlings was demonstrated using gus-tagged R. solanacearum F1C1. The same method of inoculating tomato seedlings was used with R. solanacearum GMI1000 and independent mutants of R. solanacearum GMI1000, deficient in the virulence genes hrpB, hrpG, phcA and gspD. Wildtype R. solanacearum GMI1000 was found to be virulent on tomato seedlings, whereas the mutants were found to be non-virulent. This leaf-clip technique, for inoculation of tomato seedlings, has the potential to be a valuable approach, saving time, space, labour and costs.