Two plant-associated Bacillus velezensis strains selected after genome analysis, metabolite profiling, and with proved biocontrol potential, were enhancing harvest yield of coffee and black pepper in large field trials.

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.

Population genetics unveils large-scale migration dynamics and population turnover of Spodoptera exigua.

BACKGROUND: Migration is a widespread phenomenon among many insect species, including herbivorous crop pests. At present, scant information exists on the long-range migration of the polyphagous armyworm, Spodoptera exigua and its underlying climatic determinants (i.e. East Asian or South Asian monsoon circulation). In this study, we employed a population genetics approach to delineate S. exigua migration patterns across multiple Asian countries. RESULTS: Using mitochondrial cytochrome I (COI) and microsatellite markers, low-to-moderate levels of genetic diversity were detected among 101 S. exigua populations collected across China, Pakistan and Vietnam. Haplotype diversity and nucleotide diversity did not differ between years. Two spatially explicit genetic clusters were detected, an eastern and a western clade, with the former comprising populations in the East Asia monsoon area. No genetic differentiation was recorded among armyworm populations in the year-round breeding area, nor among those of the overwintering and nonoverwintering areas. Five of the most widespread mitochondrial haplotypes reflected the extensive gene flow across at a large spatial scale. CONCLUSION: Low-to-moderate levels of genetic diversity were observed, and evidence was found for genetic clustering in certain geographical areas. Accordingly, our unique insights into S. exigua population genetics and spatiotemporal migration dynamics help to guide applied ecological studies, ecological intensification schemes or (area-wide) pest management campaigns in China and abroad. © 2021 Society of Chemical Industry.

First record of fall armyworm Spodoptera frugiperda (J.E. Smith (Lepidoptera: Noctuidae) on maize in Viet Nam.

The neotropical fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) is an important lepidopteran pest with a broad geographical distribution (Goergen et al. 2015, Early et al. 2018, Sharanabasappa et al. 2018). Larvae of S. frugiperda feed on more than 350 plant species, including several economically-important crops such as maize, sugarcane or rice (Montezano et al. 2018). Following its invasion of the African continent and of South Asia in 2016 and 2018 respectively, FAW has caused important crop losses and associated livelihood impacts (Baudron et al., 2019). During 2019, FAW rapidly spread across Southeast Asia and FAW-attributed feeding damage was recorded on maize in Viet Nam. In Viet Nam, maize is the second most important staple food crop after rice, is extensively used for livestock production and poultry feed, and thus plays a central role in sustaining rural livelihoods (Dang et al. 2004). Hence, the recent FAW invasion and the anticipated pest-induced yield losses will carry important repercussions for local maize value chains and are likely to degrade farmers' revenue base. In this study, we conducted a morphological and molecular identification of locally-collected FAW individuals to better characterize the species' invasion history in Viet Nam.