ABSTRACT
The brown planthopper (BPH), Nilaparvata lugens, is one of the most destructive pests of rice. Given the threats posed by insecticide resistance to its control, eco-friendly strategies based on microbial pathogens emerged as a promising biocontrol alternative. In the present study, we isolated a native fungal pathogen against BPH from infected BPH cadavers and preliminarily identified as a strain of Aspergillus fumigatus based on morphological and molecular methods. Laboratory bioassay revealed that this fungal strain was highly virulent to BPH both at nymphal and adult stages, with the median lethal times (LT50) of 7.5 and 5.8 days under high conidial concentration of 1 × 109 conidia mL-1. A genome-wide view of gene expressions in BPH against fungal attack was analyzed by transcriptomic sequencing and consequently a large number of differentially expressed genes that mainly involved in host immune defense and cell detoxification were found. RNAi-mediated knockdown of an upregulated gene encoding a serine protease (NlSPN) could cause a significant decrease in BPH survival. Combination of dsRNA injection and fungal infection showed an additive effect on BPH mortality, which provided clues to develop new pest management strategies against BPH.
ABSTRACT
An experiment with four treatments of control (CK), N addition (100 kg N·hm-2·a-1), P addition (50 kg P·hm-2·a-1) and N + P (100 kg N·hm-2·a-1 + 50 kg P·hm-2·a-1) were conducted to examine the responses of plant height, ground diameter, crown width, specific leaf area, and mortality of seedlings to N and P addition. Under P addition, growth rates of plant height and ground diameter of seedlings decreased significantly by 45.1% and 30.3%, respectively. Fertilization affected the mortality of main constructive tree species. N addition significantly increased seedling mortality of Castanopsis carlesii to 25.1%. Fertilization treatment significantly increased mortality of Castanopsis fargesii to 25.1%-31.3%, while N addition and P addition signi-ficantly reduced mortality of Schima superba and Machilus nanmu. Fertilization significantly decreased the importance value of S. superba and C. fargesii in the seedling community. N addition and P addition significantly increased the importance value of M. nanmu seedling. The combined N and P addition significantly decreased Shannon index and Simpson index of the seedling community. Seedling growth was mainly affected by soil ammonium, available phosphorus, total nitrogen, canopy openness, and specific leaf area. Seedling mortality was mainly affected by soil ammonium, available phosphorus and canopy openness. Synthetically, N and P addition affected seedling growth mainly by regulating soil nitrogen and phosphorus availability and changing leaf functional trait. It accelerated the death of ectomycorrhizal tree species (C. carlesii and C. fargesii), changed the importance value of constructive species in seedling community, reduced species diversity, and ultimately changed community structure of adult trees in subtropical secondary broad-leaved forest.
Subject(s)
Nitrogen , Phosphorus , China , Forests , Nitrogen/analysis , Phosphorus/analysis , Seedlings , Soil , TreesABSTRACT
Five new flavonoids, cryptoconones A-E (1-5), along with six known compounds (6-11), were isolated from the stems of Cryptocarya concinna. The structures of these compounds were elucidated on the basis of spectroscopic data interpretation, and the absolute configurations were determined via circular dichroism spectra and X-ray crystal analysis. The cytotoxic and antimicrobial activities of these compounds were also evaluated. Compounds 9 and 10 exhibited moderate cytotoxic activities against HCT116, HT-29, SW480, and MDA-MB-231 cell lines with IC50 values ranging from 6.25 to 9.35 µM. Compounds 8 and 11 exhibited antimicrobial activity against Fusarium moniliforme and Botrytis cinerea, respectively, with the same minimum inhibitory concentration of 5 µg/mL.
