Soybean mosaic virus (SMV) is a devastating disease that threatens soybean plants worldwide. The different soybean genotypes displayed different responses to SMV strains. This study aimed to investigate the response of different selected soybean cultivars to SMV infection in Egypt based on their specific genetic makeup. The symptoms of SMV infection and the viral concentration were evaluated in eight soybean cultivars (Giza 21, Giza 22, Giza 35, Giza 82, Giza 111, Crawford, H4L4, and PI416937) using ELISA assay. The results indicated that Giza 21 and Giza 35 were moderately tolerant to SMV infection, while Giza 82 was the least tolerant cultivar. Giza 22, Giza 111, and PI416937 were less tolerant; however, H4L4 and Crawford were identified as the most tolerant cultivars against SMV infection. The chi-square analysis showed a significant association between the different selected cultivars and their response against SMV infection. The PCR test showed the presence of RSV1 (3gG2), RSV1 (5gG3), and RSV3 loci, and the absence of the RSV4 locus gene. The expression analysis of the selected defense genes (EDS1, PAD4, EDR1, ERF1, and JAR) showed variations in the fold changes between infected and non-infected soybean cultivars, suggesting that these genes might play a crucial role in this pathosystem. Additionally, there was a strong positive association between the expression levels of EDR1 and ERF1. The study found the presence of RSV1 (3gG2), RSV1 (5gG3), and RSV3 loci in selected soybean cultivars, but not RSV4. The analysis of gene expression indicated that certain defense genes may play a vital role in the pathosystem. This research is the first of its kind in Egypt to genotype soybean cultivars regarding different RSV loci. The findings could be beneficial for further research on understanding the molecular mechanisms involved in SMV infection and its management.

IN tropical and subtropical regions, contamination of crops by aflatoxin B1 (AFB1) is a growing challenge. To restrict fungal growth and allow aflatoxin detoxification, there is a need to control mycotoxin contamination. Streptomyces exfoliatus has shown promise against several phytopathogenic fungi. This study aimed to explore whether S. exfoliatus could be employed as a biocontrol agent against Aspergillus flavus and AFB1 contamination. In this study, the biological control of AFB1 production by A. flavus was examined using some actinobacteria isolates. The cytotoxic activity of AFB1 and its degradation products were also evaluated. Results revealed that the most effective actinobacterium against A. flavus was isolate number 1, which was identified as S. exfoliatus. The growth, sporulation, and AFB1 production of A. flavus decreased when it was treated with a cell-free culture filtrate produced by the identified isolate. Furthermore, 20% of the cell-free culture filtrate of S. exfoliatus completely inhibited AFB1 production. The AFB1 content was also reduced in wheat samples treated with day intervals. After 21 days, no AFB1 was detected compared with those of the controls. After 3 days, 95.47% of AFB1 was degraded by the cell-free culture filtrate. The degraded AFB1 products were less toxic than the parent aflatoxin. The optimum temperature of AFB1 degradation was 30??C, but AFB1 degradation decreased as the temperature further increased. The cell-free culture filtrate remained stable for 12 months at the time of freezing. In conclusion, S. exfoliatus cell-free culture filtrates can inhibit the growth and sporulation of A. flavus as well as reduce AFB1 generation and degrade it into less harmful compounds. This appears a promising option for minimizing contamination by A. flavus, preventing aflatoxin accumulation, and enabling aflatoxin breakdown in wheat grains; this approach may be used to reduce A. flavus and AFB1 contamination in future biological control programs.