VARIABILITY IN Ralstonia solanacearum AND ECOFRIENDLY MANAGEMENT OF BACTERIAL WILT OF TOMATO
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Date
2020-08-29
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CSKHPKV. Palampur
Abstract
Bacterial wilt incited by Ralstonia solanacearum (Smith) Yabuuchi et al., is one of the major
production constraints of tomato and it causes extensive losses in Himachal Pradesh. The investigation
on the ―Variability in Ralstonia solanacearum and ecofriendly management of bacterial wilt of tomato‖
was undertaken during 2018-19 in the Department of Plant Pathology, CSK HPKV, Palampur. A
survey was conducted on the status of bacterial wilt incidence in solanaceous vegetables growing areas
in the state. The highest wilt incidence (90-100 per cent) was recorded at Solan, Shimla and Kangra
districts in tomato (Manish), tomato (Lal Sona) and brinjal (Arka Kusumkar) crops, respectively. A
total of 37 isolates of R. solanacearum were obtained from the wilt affected tomato, brinjal, chilli and
bell pepper plants i.e. 21 from tomato, 7 from brinjal, 8 from bell pepper and one from chilli and the
isolates were designated as RS-1 to RS-37. The production of pink or light red coloured colonies with
whitish margin and EPS on TZC medium by the bacterial isolates indicated that all the R.
solanacearum isolates were virulent. All physiological/biochemical tests were used for the
identification of R. solanacearum isolates. Gram‘s staining and potassium hydroxide solubility test
revealed that all the isolates were gram negative. Variable results were observed during hydrolytic
extracellular enzymes, carbohydrate fermentation and hydrogen sulfide and indole test. The biovar test
using the oxidization of disaccharides (sucrose, lactose, maltose) and sugar alcohols (manitol, sorbitol
and dulcitol) by R. solanacearum isolates confirmed that all the isolates belonged to biovar III. The
race identification of R. solanacearum isolates by pathogenicity test on brinjal, tomato, bell pepper and
chillis indicated a broad host range and were categorized as race 1. The in vitro evaluation of different
varieties against R. solanacearum showed that 4 tomato varieties (LS-89, Hawaii 7996, Hawaii 7998,
Palam Pride), 2 brinjal varieties (Arka Keshav, Arka Nidhi) and 2 chilli varieties (PI201232, VI037556) were found resistant to bacterial wilt. Among six bioagents, Pseudomonas fluorescens and
Trichoderma koningii (DMA-8) showed maximum inhibition zones of 21.67mm and 12.33mm against
R. solanacearum, respectively with paper disc method. In case of botanicals, eucalyptus (Eucalyptus
spp.) showed highest inhibition zone (6.73mm) followed by neem (Azadirachta indica) with 6.56mm at
20% conc. Similarly, among the organic inputs tamar lassi at 5% concentration showed maximum
growth inhibition (99.21%) followed by Himsol (93.01%) through poison food technique whereas,
Agniastra, Beejamrit and Lantana Ark were found ineffective in inhibiting the growth of R.
solanacearum. The maximum survivability of the seedlings was 12.01 days followed by 4.41 days
when the seedlings were dipped in a combination of tamar Lassi + Himsol+ Panchgavya and tamar
lassi alone for 60 minutes at 15% concentration, respectively