ABSTRACT
Elimination of chemically synthesized pesticides, such as fungicides and nematicides, in agricultural products is a key to successful practice of the Vietnamese agriculture. We describe here the route for developing successful biostimulants based on members of the Bacillus subtilis species complex. A number of endospore-forming Gram-positive bacterial strains with antagonistic action against plant pathogens were isolated from Vietnamese crop plants. Based on their draft genome sequence, thirty of them were assigned to the Bacillus subtilis species complex. Most of them were assigned to the species Bacillus velezensis. Whole genome sequencing of strains BT2.4 and BP1.2A corroborated their close relatedness to B. velezensis FZB42, the model strain for Gram-positive plant growth-promoting bacteria. Genome mining revealed that at least 15 natural product biosynthesis gene clusters (BGCs) are well conserved in all B. velezensis strains. In total, 36 different BGCs were identified in the genomes of the strains representing B. velezensis, B. subtilis, Bacillus tequilensis, and Bacillus. altitudinis. In vitro and in vivo assays demonstrated the potential of the B. velezensis strains to enhance plant growth and to suppress phytopathogenic fungi and nematodes. Due to their promising potential to stimulate plant growth and to support plant health, the B. velezensis strains TL7 and S1 were selected as starting material for the development of novel biostimulants, and biocontrol agents efficient in protecting the important Vietnamese crop plants black pepper and coffee against phytopathogens. The results of the large-scale field trials performed in the Central Highlands in Vietnam corroborated that TL7 and S1 are efficient in stimulating plant growth and protecting plant health in large-scale applications. It was shown that treatment with both bioformulations resulted in prevention of the pathogenic pressure exerted by nematodes, fungi, and oomycetes, and increased harvest yield in coffee, and pepper.
ABSTRACT
Objetivou-se estudar a dispersão espacial da mancha manteigosa em cafeeiro, por meio de arranjos espaciais e da análise da dinâmica e estruturas de focos da doença durante três anos consecutivos. Nesse período, não houve progresso da doença no campo. Sob plantas doentes, surgiam mudas com sintomas da doença, um indício da transmissibilidade via semente. Constatou-se um total de 10 focos, com média de 2,5 plantas/focos e com tendência desses focos (maior número de plantas sintomáticas) na direção das linhas de plantios, tendo disposição de forma elíptica. Observou-se número elevado de focos unitários, correspondendo a 52 por cento das plantas doentes. Pelas análises de seqüências ordinárias runs e doublet verificou-se padrão espacial aleatório. Tal fato indica que a mancha manteigosa ocorre a partir de plantas isoladas (focos unitários) e que a principal via de transmissão é a semente (semente/planta/semente).
The aim of this study was to analyze the spatial dispersion pattern of the blister spot on coffee trees, through spatial arrangements and the analysis of the dynamics and foci structure of the disease during three consecutive years. No disease progress was observed in this area during the period of study. Seedlings showing disease symptoms were found under the canopy of diseased trees, strongly indicating that the disease may be transmitted through the seeds. Ten foci with 2.5 trees per focus were observed in the studied area. The foci were distributed following the plant rows with elliptical shape. Unitary foci predominated in the area in 52 percent of the diseased trees. Analyses of runs and doublets showed a random spatial pattern of the disease. These results evidenced that the blister spot occurs from isolated plants (unitary foci) and this characteristic may possibly be explained if the seeds are the main disease transmission agent (seed-plant-seed).
