Metagenomics approaches in unveiling the dynamics of Plant Growth-Promoting Microorganisms (PGPM) vis-à-vis Phytophthora sp. suppression in various crop ecological systems.

Phytophthora species are destructive pathogens causing yield losses in different ecological systems, such as potato, black pepper, pepper, avocado, citrus, and tobacco. The diversity of plant growth-promoting microorganisms (PGPM) plays a crucial role in disease suppression. Knowledge of metagenomics approaches is essential for assessing the dynamics of PGPM and Phytophthora species across various ecosystems, facilitating effective management strategies for better crop protection. This review discusses the dynamic interplay between PGPM and Phytophthora sp. using metagenomics approaches that sheds light on the potential of PGPM strains tailored to specific crop ecosystems to bolster pathogen suppressiveness.

Diversity and functional characteristics of culturable bacterial endosymbionts from cassava whitefly biotype Asia II-5, Bemisia tabaci.

Whitefly Bemisia tabaci, a carrier of cassava mosaic disease (CMD), poses a significant threat to cassava crops. Investigating culturable bacteria and their impact on whiteflies is crucial due to their vital role in whitefly fitness and survival. The whitefly biotype associated with cassava and transmitting CMD in India has been identified as Asia II 5 through partial mitochondrial cytochrome oxidase I gene sequencing. In this study, bacteria associated with adult B. tabaci feeding on cassava were extracted using seven different media. Nutrient Agar (NA), Soyabean Casein Digest Medium (SCDM), Luria Bertani agar (LBA), and Reasoner's 2A agar (R2A) media resulted in 19, 6, 4, and 4 isolates, respectively, producing a total of 33 distinct bacterial isolates. Species identification through 16SrRNA gene sequencing revealed that all isolates belonged to the Bacillota and Pseudomonadota phyla, encompassing 11 genera: Bacillus, Cytobacillus, Exiguobacterium, Terribacillus, Brevibacillus, Enterococcus, Staphylococcus, Brucella, Novosphingobium, Lysobacter, and Pseudomonas. All bacterial isolates were tested for chitinase, protease, siderophore activity, and antibiotic sensitivity. Nine isolates exhibited chitinase activity, 28 showed protease activity, and 23 displayed siderophore activity. Most isolates were sensitive to antibiotics such as Vancomycin, Streptomycin, Erythromycin, Kanamycin, Doxycycline, Tetracycline, and Ciprofloxacin, while they demonstrated resistance to Bacitracin and Colistin. Understanding the culturable bacteria associated with cassava whitefly and their functional significance could contribute to developing effective cassava whitefly and CMD control in agriculture. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-024-03949-0.

Invasive flower thrips, Thrips parvispinus (Karny) occurrence, host expansion and genetic diversification in a tropical poly-crop ecosystem.

BACKGROUND: Invasive black flower thrips Thrips parvispinus (Karny) has recently emerged as a significant threat to Indian chilli production. Identifying T. parvispinus became difficult due to the complex presence of thrips species in Indian chilli and allied ecosystems. Pest management success depends on assessing invasive pests genetic populations and their distribution in newly habituated areas. METHODS AND RESULTS: The current study investigated the genetic diversity and phylogeographic structure of T. parvispinus across major chilli-growing zones representing different agro-climatic conditions in Tamil Nadu. The species-specific chaetotaxy characteristics of T. parvispinus and molecular analysis of the mtCOI gene were used to confirm that the species T. parvispinus has expanded rapidly in three regions (North Western, Western and Cauvery delta), sparsely in one (Southern) and absent from two (hilly and high rainfall). Fifteen allied crops in chilli/capsicum growing tracts served as host plants for T. parvispinus. A shrub species, namely Littleleaf boxwood, Buxus microphylla Siebold & Zucc., is described as a host plant for the first time. On capsicum and chilli, T. parvispinus and Scirtothrips dorsalis coexisted. Thrips palmi, T. tabaci, Frankliniella schultzei, and Microcephalothrips abdominalis co-occurring alongside T. parvispinus on allied crops. CONCLUSION: Molecular characterization and haplotype identification help define the genetic composition of T. parvispinus and serve as a foundation for efficient monitoring and creation of Integrated Pest Management (IPM) strategies. As a result, the genetic data presented in this work strongly argues that T. parvispinus as a population is resolving itself towards a fixed state through natural selection that spans its native range globally along with low genetic diversity [Hd: 0.771].

Complete Genome Sequence Analysis of Bacillus subtilis Bbv57, a Promising Biocontrol Agent against Phytopathogens.

Plant growth-promoting rhizobacteria (PGPR) are a group of root-associated beneficial bacteria emerging as one of the powerful agents in sustainable plant disease management. Among the PGPR, Bacillus sp. has become a popular biocontrol agent for controlling pests and the diseases of several crops of agricultural and horticultural importance. Understanding the molecular basis of the plant growth-promoting and biocontrol abilities of Bacillus spp. will allow us to develop multifunctional microbial consortia for sustainable agriculture. In our study, we attempted to unravel the genome complexity of the potential biocontrol agent Bacillus subtilis Bbv57 (isolated from the betelvine's rhizosphere), available at TNAU, Coimbatore. A WGS analysis generated 26 million reads, and a de novo assembly resulted in the generation of 4,302,465 bp genome of Bacillus subtilis Bbv57 containing 4363 coding sequences (CDS), of which 4281 were functionally annotated. An analysis of 16S rRNA revealed its 100% identity to Bacillus subtilis IAM 12118. A detailed data analysis identified the presence of >100 CAZymes and nine gene clusters involved in the production of secondary metabolites that exhibited antimicrobial properties. Further, Bbv57 was found to harbor 282 unique genes in comparison with 19 other Bacillus strains, requiring further exploration.

Novel and stable QTL regions conferring resistance to MYMV disease and its inheritance in blackgram (Vigna mungo (L.) Hepper).

Mungbean yellow mosaic virus (MYMV) disease is a significant constraint for blackgram production. The present study employed a mapping population derived from a cross between susceptible (MDU 1) and resistant (TU 68) genotypes to identify quantitative trait loci (QTL) associated with MYMV disease resistance in addition to bruchine resistance loci identified from the previous study. Phenotyping was carried out in F2 generation under the disease spreader row method at field condition. Disease score observations were carried out 60 days after sowing (DAS). The chi-square goodness of fit test revealed inhibitory gene action with two genes controlling the expression of resistance to MYMV disease. However, QTL analysis revealed one major QTL region, i.e. qMYMVD_60 at LG 10 responsible for MYMV disease score at 60 DAS, accounted for 21 per cent of variation. The identified QTL has the flanking markers as CEDG180 and CEDG116. Hence, the QTL, qMYMVD_60 may be utilized in the breeding of MYMV disease resistance. Further, the marker-assisted introgression of both the MYMV and bruchine resistance QTLs can be performed in the near future.