Junsheng Huang

Fusarium oxysporum f. sp. cubense (Foc) causes banana Fusarium wilt disease, which is a destructive soil-borne disease. Many plants can recruit rhizosphere microorganisms using their root exudates, thereby shaping the rhizosphere microbiome to resist pathogen infection. Therefore, this study was conducted to explore the role of root exudates in the process of biocontrol strain colonization and resistance to pathogens. In this study, the banana root exudates used as chemoattractants were obtained by hydroponics. Bacillus velezensis strain LG14-3 was isolated from the infected area of the root system of banana and showed significant chemotaxis to banana root exudates and strong inhibition of Fusarium oxysporum f. sp. cubense. Further analysis found that LG14-3 showed chemotaxis toward the components of banana root exudates, such as citric acid, succinic acid, glycine, D-galactose and D-maltose, and glycine and citric acid, which resulted in more significant chemotaxis of LG14-3. Moreover, banana root exudates enhanced the swarming motility and biofilm formation of LG14-3. Pot experiments showed that glycine and citric acid enhanced the colonization ability of Bacillus velezensis LG14-3 in the banana rhizosphere and reduced the disease severity index of banana fusarium wilt. Glycine and citric acid enhanced the growth-promoting ability of LG14-3 under pathogen stress. Our results showed that the addition of chemotactic substances enhanced the biocontrol potential of Bacillus velezensis LG14-3 to prevent banana Fusarium wilt.

Coriander ( Coriandrum sativum ) is a medicinal and aromatic plant. From November 2017 to March 2020, leaf blight disease on coriander plants was frequently observed in commercial coriander cultivated fields of Haikou, Sanya and Wanning City, Hainan Province, China. Leaves with symptoms showed irregular chlorotic to dark brown necrotic lesions at the edges of leaves, and the leaves were curled and covered with a layer of grey mould. Based on morphological characteristics, pathogenicity testing and concatenated sequences of the internal transcribed spacer region (ITS), actin ( ACT ) and translation elongation factor‐1α ( TEF ) genes, the pathogen was identified as Cladosporium tenuissimum . Untargeted metabolomes of the coriander leaves were analysed by gas chromatography‐mass spectrometry (GC‐MS). Score plots of principal component analysis (PCA) and partial least squares discriminant analysis (PLS‐DA) showed clear discrimination between infected and control treatments. The levels of l ‐threonic acid, hexadecanoic acid and myo ‐inositol in the control treatment were 3.45‐, 1.81‐ and 2.44‐fold, respectively, those in the infected treatment. To our knowledge, this is the first report of C . tenuissimum causing coriander leaf blight disease in China. Furthermore, this study indicates that C . tenuissimum infection of coriander causes a significant decrease in l ‐threonic acid, hexadecanoic acid and myo ‐inositol levels, indicating that these metabolites may be involved in the plant's response to coriander leaf blight disease.

(1) Background: Ralstonia solanacearum causes tomato bacterial wilt disease, one of the most serious tomato diseases. As the combination of Trichoderma virens (Tvien6) and Bacillus velezensis (X5) was more effective at controlling tomato bacterial wilt disease than a single agent, we investigated the synergistic effect of Tvien6 and X5 in controlling this disease; (2) Methods: The disease incidence, plant heights and weights, relative chlorophyll content (SPAD values), defensive enzymes (PPO, POD, and SOD) activities, and metabolome were estimated among four treatment groups (BR treatment, X5 + R. solanacearum (RS-15); TR treatment, Tvien6+ RS-15; TBR treatment, Tvien6 + X5 + RS-15; and R treatment, RS-15); (3) Results: The R treatment group had the highest disease incidence and lowest plant heights, plant weights, SPAD values, defensive enzyme activities, and D-fructose and D-glucose contents; the TBR treatment group had the lowest disease incidence and highest plant heights, plant weights, SPAD values, defensive enzyme activities, and D-fructose and D-glucose contents; (4) Conclusions: The results revealed that Tvien6 and X5 can both individually promote tomato plant growth, increase leaf chlorophyll content, enhance defensive enzyme activities, and induce the accumulation of D-fructose and D-glucose; however, they were more effective when combined.

Banana streak virus (BSV) is a significant constraint to banana production and genetic improvement. It is necessary to develop and use BSV detection strategies that are both reliable and sensitive for the management of the virus. A loop‐mediated isothermal amplification (LAMP) assay was developed and evaluated for the detection of BSV. Four primers matching a total of six sequences of the conserved ORF III polyprotein genes were synthesized for developing a specific and sensitive LAMP for DNA extracts from field‐infected banana plants. LAMP assay could detect as low as 1 pg/μl template DNA. Test results of all field samples collected from different regions of South China showed that LAMP is more sensitive than PCR. This relatively simple and sensitive technique showed excellent potential with field‐collected samples and for routine screening of tissue culture materials in South China.

Language learner strategies (LLS) have long been viewed as a variable of individual differences, or as cognitive skills. This study, focusing as it does on the data taken from a series of focus groups with 47 senior secondary students in mainland China, seeks a new interpretation of strategy development and use from a sociocultural perspective. Evidence provided from the focus-group discussions shows that in the mainstream exam-orientated culture in mainland China, the grade-getting goal was likely to determine the general orientation of strategies for a variety of classroom learning tasks and shape the changes in strategy use over time which emerge at different learning stages. The results also indicate that the processes of strategy development and use were mediated by learners' personal discourse patterns embedded in their situated learning experience; by cultural artifacts (tasks); and by interpersonal interactions with their teachers, peers and family members; and situated in their communities of language learning practices and social cultures. In addition, the study underlines the need to take into account learning goals and the nature of learning tasks in LLS research, and to create a situated strategy development community as part of strategy instruction or training programs.