H.B.P.Sandani
University of Ruhuna, Sri Lanka
Title: Biocontrol efficacy of two Bacillus species against chilli pepper anthracnose causal agent Colletotrichum truncatum
Submitted Date: 28-02-2019
Biography
H.B.P.Sandani is a PhD candidate from Ruhuna University, Sri Lanka. She conducted her PhD research project in biotechnology and crop protection. She has got 18 research publications including three full length research articles in referred journals, extended abstracts and abstracts. Her ambition is to do a great contribution for the world food production through a green approach with the help of her research findings.
Abstract
Applicability of two Bacillus strains isolated from standard compost was assessed as a reliable alternative in the management of the anthracnose in chilli pepper. Out of twenty promising antagonistic bacterial isolates, two were genotypically characterized as Bacillus spp. based on 16 S rRNA analysis. Selected two antagonistic Bacillus strains significantly suppressed the mycelial growth and the spore germination of chilli pepper anthracnose causal agent Colletotrichum truncatum (p<0.05). Malformation of the fungal hyphae was dominant in the area subjected to antagonism. One of the major antagonistic mechanisms extended towards the anthracnose pathogen C. truncatum by these two Bacillus strains was detected as antibiosis in the cellophane overlay technique. They produced antifungal peptides, lipopeptides and also minute amount of organic solvent soluble molecules as antifungal compounds against C. truncatum. These antifungal compounds showed minimum inhibitory concentrations of 3200 ppm and 2460 ppm on C. truncatum. Also these metabolites are thermally stable up to 120 ºC while they could retain the antifungal properties more than 10 weeks under cold conditions and up to eight weeks at room temperature. One of the Bacillus strains produces a bacteriocin like small peptide inhibitory against C. truncatum. Induction of latent host defense mechanisms is another antagonistic mechanism employed by this Bacillus sp. upon C. truncatum infection in chilli pepper. The tested Bacillus sp. could enhance the expression of defense related PAL and PO enzymes in chilli pepper plants upon C. truncatum infection. Also these antagonistic Bacillus strains promote chilli pepper plants’ growth through the production of significant amounts of Indole Acetic Acid (IAA) which is a growth hormone as an indirect mechanism against C. truncatum. Also they showed a prominent swimming and swarming ability indicating their high potentiality in colonizing plant tissues paving the way for successful green house and field applications. These two strains effectively managed the seed borne infection of C. truncatum resulting healthy chilli pepper seedlings with good vigour. Also they effectively managed the fruit decay caused by C. truncatum at colour breaking stage and green stage suggesting the suitability of Bacillus spp. as a potential candidate to be used in the development of a biocontrol agent against chilli pepper anthracnose causal agent C. truncatum. \r\nKey words: Anthracnose, Antibiosis, Bacillus spp., Chilli pepper, C. truncatum, Defense induction, Growth promotion\r\n