Feixue Cheng

Development and Evaluation of Loop-Mediated Isothermal Amplification Assay for Rapid Detection of Tylenchulus semipenetrans Using DNA Extracted from Soil

Tylenchulus semipenetrans is an important and widespread plant-parasitic nematode of citrus worldwide and can cause citrus slow decline disease leading to significant reduction in tree growth and yield. Rapid and accurate detection of T. semipenetrans in soil is important for the disease forecasting and management. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed to detect T. semipenetrans using DNA extracted from soil. A set of five primers was designed from the internal transcribed spacer region (ITS1) of rDNA, and was highly specific to T. semipenetrans. The LAMP reaction was performed at 63°C for 60 min. The LAMP product was visualized directly in one reaction tube by adding SYBR Green I. The detection limit of the LAMP assay was 10−2 J2/0.5 g of soil, which was 10 times more sensitive than conventional PCR (10−1 J2/0.5 g of soil). Examination of 24 field soil samples revealed that the LAMP assay was applicable to a range of soils infested naturally with T. semipenetrans, and the total assay time was less than 2.5 h. These results indicated that the developed LAMP assay is a simple, rapid, sensitive, specific and accurate technique for detection of T. semipenetrans in field soil, and contributes to the effective management of citrus slow decline disease.

Biodegradation of fenpropathrin by a novel Rhodopseudomonas sp. strain PSB07-8

The aim of our study was to isolate a fenpropathrin-degrading bacterial strain and to determine its effectiveness in bioremediating fenpropathrin-contaminated soil in the laboratory. We isolated a bacterial strain from soils and named it as PSB07-8, and showed that this organism was able to degrade pyrethroid pesticide fenpropathrin. The organism was identified as a strain of Rhodopseudomonassp.The strain PSB07-8 degraded fenpropathrin in a co-metabolic way, and the optimal condition of degradation was at temperature of 30°C and pH value of 7. Moreover, the strain PSB07-8 could effectively degrade cypermethrin and bipthenthrin, but only slightly for deltemethrin, cyfluthrin and esfenralerate. We found that the degradation rate was negatively correlated with the fenpropathrin concentration in a certain range. In addition, our soil degradation test showed that in sterilised soils with 20 mg/l or 40 mg/l fenpropathrin, the strain PSB07-8 could complete 100% or achieve 44.7% of fenpropathrin degradation in 15 days. To our best knowledge, this is the first report of a strain of genus Rhodopseudomonas with an ability of degrading fenpropathrin in soil.

First Report of Meloidogyne graminicola on Rice (Oryza sativa) in Hunan Province, China

Meloidogyne graminicola is an important pathogen of rice (Oryza sativa L.), and can cause yield losses of 11 to 80% (Mantelin et al. 2017). In June 2016, rice (cv. Fengyuanyou 2297) growing in direct seeding rice field in Hetang District, Zhuzhou City, Hunan Province, China, were observed with symptoms of leaf yellowing, stunting and many hook-shaped galls on the roots. Females, males and egg masses of Meloidogyne spp. were found within the galls after dissection. The morphological characteristics of females, males and second-stage juveniles (J2s) were observed and measured under an optical microscope at 100× and 400× magnification. The perineal patterns of females were dorsoventrally oval with low to moderately high and round dorsal arches and lacking obvious lateral lines; striae were usually smooth and fine, and broken by short and irregular striae in the dorsal part of the pattern; phasmids were small, distinct, and close together. Morphological measurements of females (n = 20) included body length (L...

Complete genome sequence of Bacillus thuringiensis YC-10, a novel active strain against plant-parasitic nematodes

Bacillus thuringiensis is an important microbial biopesticide for controlling agricultural pests by the production of toxic parasporal crystals proteins.Here,we report the finished annotated genome sequence of B. thuringiensis YC-10,which is highly toxic to nematodes.The complete genome sequence consists of a circular chromosome and nine circular plasmids,which the biggest plasmid harbors six parasporal crystals proteins genes consisting of cry1Aa, cry1Ac, cry1Ia, cry2Aa, cry2Ab and cryB1. The crystals proteins of Cry1Ia and Cry1Aa have high nematicidal activity against Meloidogyne incognita.