Control ofRhizoctonia solani andSclerotium rolfsii in the greenhouse using endophyticBacillus spp.

Abstract

Isolates of different endophytic bacteria were recovered from surface-disinfected seeds obtained from commercial companies, plants in the field and tissue culture. The bacteria were isolated from seeds after stringent surfacedisinfection. Pseudomonas fluorescens (isolate no. 14) from bean inhibited growth of all fungi tested and was fluorescent on King B medium. Bacillus cereus from Sinapis (isolate no. 65) inhibited growth of Rhizoctonia solani, Pythium ultimum and Sclerotium rolfsii and also exhibited chitinase activity. Bacillus subtilis from onion tissue culture (isolate no. 72) inhibited R. solani and P. ultimum growth. B. cereus from cauliflower (isolate no. 78) inhibited growth of R. sotani. B. pumilus from sunflower (isolate no. 85) inhibited growth of R. solani and S. rolfsii. B. cereus (isolate no. 65) was introduced into cotton, and by using radioactive labelling we found that it was present for 16 days in the root-stem junction. It is most likely that these bacteria were still found 72 days after their introduction in the root and stem, at levels of 2.8.105 and 5.104 cfu g-1 fresh weight, respectively, when selective medium was used. There was no difference between control and treated plants in their height or in the fresh weight of roots, stems and leaves.When cotton seedlings were inoculated with B. cereus (isolate no. 65), B. subtilis (isolate no. 72) or B. pumilus (isolate no. 85), disease incidence caused by Rhizoctonia solani was reduced in the greenhouse by 51%, 46% and 56%, respectively. In bean seedlings inoculated with B. subtilis (isolate no. 72), B. cereus (isolate no. 78) or B. pumilus (isolate no. 65), disease incidence caused by Sclerotium rolfsii was reduced by 72%, 79% and 26%, respectively, as compared to control. In both cotton and bean seedlings, these endophytes reduced the disease index more than 50%. These results indicate that endophytic bacteria can survive inside cotton plants and are efficient agents for biological control against plant pathogens under greenhouse conditions.

Nature and role of root exudates: Efficacy in bioremediation

“…present in the rice rhizosphere. Endophytic bacteria appear to be ever-present in most plant species, inducing beneficial effects, as incidental from their ability to promote plant growth (Bacilio et al, 2001) to confer resistance against plant pathogens (Benhamou et al, 1996;Hallmann et al, 1997;Pleban et al, 1995).…”

Seleção de bactérias endofíticas de tomateiro como potenciais agentes de biocontrole e de promoção de crescimento

“…Os primeiros relatos as consideravam contaminantes resultantes da desinfestação superficial incompleta ou patógenos fracamente virulentos (HOLLIS, 1951;THOMAS & GRAHAM, 1952). Porém, pesquisas mais recentes demonstraram que as bactérias endofíticas são habitantes naturais do interior das plantas e podem reduzir os sintomas causados por diversos fitopatógenos e promover o crescimento de seus hospedeiros (CHEN et al, 1995;FROMMEL et al, 1991;PEER & SCHIPPERS, 1989;PLEBAN et al, 1995).…”

“…vasinfectum (CHEN et al, 1995) e Rhizoctonia solani (PLEBAN et al, 1995) em algodão; Sclerotium rolfsii em feijão (PLEBAN et al, 1995); Pythium myriotylum, R. solani, Gaeumannomyces graminis e Heterobasidium annosum em arroz (MUKHOPADHYAY et al, 1996), entre outros. Com relação às doenças bacterianas, as bactérias endofíticas foram eficientes como agentes de biocontrole de Xanthomonas campestris pv.…”

Improvement in symbiotic efficiency of chickpea (Cicer arietinum) by coinoculation of Bacillus strains with Mesorhizobium sp. Cicer

“…Recently, Bacillus strains isolated from plant tissues or soil have been reported to inhibit the growth of phytopathogenic fungi Gaeumannomyces graminis var. tritici 9 , Rhizoctonia solani, Pythium ultimum and Sclerotium rolfsi 21 . Seed bacterization effect on chickpea seedlings: Five Bacillus strains i.e.…”