Background: Pre-harvest infection of peanuts byAspergillus flavusand subsequent aflatoxin contamination is one of the food safety factors that most severely impair peanut productivity and human and animal health, especially in arid and semi-arid tropical areas. Some peanut cultivars with natural pre-harvest resistance to aflatoxin contamination have been identified through field screening. However, little is known about the resistance mechanism, which has slowed the incorporation of resistance into cultivars with commercially acceptable genetic background. Therefore, it is necessary to identify resistance-associated proteins, and then to recognize candidate resistance genes potentially underlying the resistance mechanism.Results: The objective of this study was to identify resistance-associated proteins in response toA. flavusinfection under drought stress using two-dimensional electrophoresis with mass spectrometry. To identify proteins involved in the resistance to pre-harvest aflatoxin contamination, we compared the differential expression profiles of seed proteins between a resistant cultivar (YJ-1) and a susceptible cultivar (Yueyou 7) under well-watered condition, drought stress, andA. flavusinfection with drought stress. A total of 29 spots showed differential expression between resistant and susceptible cultivars in response toA. flavusattack under drought stress. Among these spots, 12 protein spots that consistently exhibited an altered expression were screened by Image Master 5.0 software and successfully identified by MALDI-TOF MS. Five protein spots, including Oso7g0179400, PII protein, CDK1, Oxalate oxidase, SAP domain-containing protein, were uniquely expressed in the resistant cultivar. Six protein spots including low molecular weight heat shock protein precursor, RIO kinase, L-ascorbate peroxidase, iso-Ara h3, 50 S ribosomal protein L22 and putative 30 S ribosomal S9 were significantly up-regulated in the resistant cultivar challenged byA. flavusunder drought stress. A significant decrease or down regulation of trypsin inhibitor caused byA. flavusin the resistant cultivar was also observed. In addition, variations in protein expression patterns for resistant and susceptible cultivars were further validated by real time RT-PCR analysis.Conclusion: In summary, this study provides new insights into understanding of the molecular mechanism of resistance to pre-harvest aflatoxin contamination in peanut, and will help to develop peanut varieties with resistance to pre-harvested aflatoxin contamination.

Asian soybean rust (ASR), caused by Phakopsora pachyrhizi (Syd.), poses a serious threat to global soybean production. The main approach to managing this disease has been through repeated fungicide applications which have reduced efficacy due to fungicide resistance. Recently, spray-induced gene silencing (SIGS) through exogenous application of double-stranded RNA (dsRNA) has emerged as a promising approach for plant disease management. In the present study, twelve different dsRNAs targeting genes important for P. pachyrhizi urediniospore germination, infection of the host plant or resistant to commonly used fungicides were produced in Escherichia coli on a large scale. Nine of these dsRNAs significantly reduced ASR severity (by 24.0% to 81.1%) and fungal biomass (50.5% to 83.1%) compared to the control when applied as a foliar spray in our growth chamber studies. Three of the most effective dsRNAs targeting an acyltransferase (ACE), cytochrome B (CYTB1) and a reductase (S12) also significantly reduced disease severity (78.2 to 82.3%) and fungal growth (79.8 to 85.4%) compared to the control in the greenhouse studies. Further investigation of the P. pachryrhizi urediniospore germination and hyphal growth in the presence of these dsRNAs in vitro revealed these dsRNAs reduced the spore germination rate from 72.1% to 0.0–26.6% at 4.5 h and hyphal growth from 254.0 µm to 2.7–40.5 µm at 9 h, with dsRNA targeting the S12 gene being the most effective. These results highlight the potential of SIGS using selected dsRNAs as a sustainable strategy for managing ASR through suppressing urediniospore germination and hyphal growth.