ABSTRACT
Erionota torus (Evans, 1941) is a banana pest and is mainly distributed in Southeast Asia and the Pacific regions. The complete mitogenome of E. torus (GenBank accession number MW586888) is 15,987 bp in size, including 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs genes, and a noncoding A + T-rich region. The A + T-rich region is located between 12S rRNA and tRNAMet . The base composition of the whole E. torus mitogenome is 39.68% for A, 7.30% for G, 41.55% for T, and 11.47% for C, with a high AT content of 81.23%. The phylogeny analysis indicated that E. torus had a close relationship with Notocrypta curvifascia. The present data could contribute to the further detailed phylogeographic analysis and provide a comprehensive control strategy for this banana pest.
ABSTRACT
Fusarium wilt of banana, caused by Fusarium oxysporum f. sp. cubense (Foc), especially Tropical Race 4 (TR4), seriously threatens banana production worldwide. There is no single effective control measure, although certain Bacillus strains secrete antibiotics as promising disease-biocontrol agents. This study identified five Bacillus strains displaying strong antibiotic activity against TR4, using a systemic assessment for presence/absence of genetic markers at genome level, and expression profiles at transcriptome level. A conventional PCR with 13 specific primer pairs detected biocontrol-related genes. An accurate, quantitative real-time PCR protocol with novel designed specific primers was developed to characterise strain-specific gene expression, that optimises strain-culturing and RNA-isolation methodologies. Six genes responsible for synthesising non-ribosomal peptide synthetase biocontrol metabolites were detected in all five strains. Three genes were involved in synthesising three Polyketide synthetase metabolites in all five strains, but the macrolactin synthase gene mln was only detected in WBN06 and YN1282-2. All five Bacillus strains have the genes dhb and bioA, essential for synthesising bacillibactin and biotin. However, the gene sboA, involved in subtilisin synthesis, is absent in all five strains. These genes' expression patterns were significantly different among these strains, suggesting different mechanisms involved in TR4 biocontrol. Results will help elucidate functional genes' biocontrol mechanisms.
ABSTRACT
BACKGROUND AND OBJECTIVES: The biocontrol agent Aphidius gifuensis has widely been released and applied since 1997 to control Myzus persicae in tobacco fields of Yunnan Province, southwestern China, but its ecological effects on the local insect community and diversity have not been described. Biological control agents may effect a diversity of organisms as well as the target for control but such trophic cascades have seldom been studied. This study aimed to explore the effects of A. gifuensis on the insect community and diversity in tobacco fields after long-term release and expansion of the biocontrol agent in Yunnan Province. MATERIALS AND METHODS: The effects of A. gifuensis on species composition, importance value, species richness, diversity indices and evenness index were studied for insect community samples obtained via field surveys and malaise trap collection in Yunnan Province. RESULTS: A total of 39 insect species and 1 spider, principally belonging to 40 families and 13 orders in tobacco fields of Yunnan Province were identified. Among these, there were 20 pests, 14 natural enemies and 6 others, constituting 50, 35 and 15% of total species sampled, respectively. Within insect communities, M. persicae, Empoasca flavescens and Drosophila melanogaster were the dominant species and Spodoptera litura, one unidentified species (Ichneumonidae), Sphex haemorrhoidalis, Vespa veutinaauraris, Aedes albopictus, A. gifuensis and Liriomyza huidobrensis were the subdominant species. From June to August, the relative density of A. gifuensis gradually increased and concomitantly the total relative density of other natural enemies exhibited a slight decline in July and marked increase in August. The relative density of M. persicae significantly increased in July and then declined precipitously in August. Moreover, the values of Simpson index, Shannon-Wiener index and Pielou index were greater than 0.50, 1.50 and 0.50, respectively, indicating high insect diversity. CONCLUSION: Beneficial insects, in addition to the biocontrol agent are relatively abundant in tobacco fields of Yunnan Province, marking improvement in the local insect community diversity after a long-term release of the biocontrol agent A. gifuensis, which, by land area, constitutes one of the largest natural enemy control programs in the world.
Subject(s)
Aphids/physiology , Insecta/physiology , Animals , Biodiversity , Biological Control Agents/metabolism , China , Ecosystem , NicotianaABSTRACT
Banana is the most popular and most exported fruit and also a major food crop for millions of people around the world. Despite its importance and the presence of serious disease threats, research into this crop is limited. One of those is Panama disease or Fusarium wilt. In the previous century Fusarium wilt wiped out the "Gros Michel" based banana industry in Central America. The epidemic was eventually quenched by planting "Cavendish" bananas. However, 50 years ago the disease recurred, but now on "Cavendish" bananas. Since then the disease has spread across South-East Asia, to the Middle-East and the Indian subcontinent and leaped into Africa. Here, we report the presence of Fusarium oxysporum f.sp. cubense Tropical Race 4 (Foc TR4) in "Cavendish" plantations in Laos, Myanmar, and Vietnam. A combination of classical morphology, DNA sequencing, and phenotyping assays revealed a very close relationship between the Foc TR4 strains in the entire Greater Mekong Subregion (GMS), which is increasingly prone to intensive banana production. Analyses of single-nucleotide polymorphisms enabled us to initiate a phylogeography of Foc TR4 across three geographical areas-GMS, Indian subcontinent, and the Middle East revealing three distinct Foc TR4 sub-lineages. Collectively, our data place these new incursions in a broader agroecological context and underscore the need for awareness campaigns and the implementation of validated quarantine measures to prevent further international dissemination of Foc TR4.
