Efficacy of Saccharothrix algeriensis NRRL B-24137 to suppress Fusarium oxysporum f.sp. vasinfectum induced wilt disease in cotton.

Fusarium cotton wilt is a devastating disease of the cotton crop throughout the world, caused by Fusarium oxysporum f.sp. vasinfectum (FOV). Chemical control has many side effects, so, biological controls have been widely used for the management of Fusarium wilt. This study aimed to investigate the possible use of an actinomycetes Saccharothrix algeriensis (SA) NRRL B-24137 to control FOV. To access in-vitro anti-Fusarium ability of SA NRRL B-24137, dual culture assay, spore germination and seed germination tests were carried out. Following in-vitro investigations, several pot tests in a greenhouse environment were used to evaluate the biological control potential of SA NRRL B-24137 against FOV. Dual culture assay and spore germination revealed that SA NRRL B-24137 showed significant anti-Fusarium activity.During spore germination 87.77% inhibition of spore germination were observed. In pot experiments, SA NRRL B-24137 primed cotton seeds resulted in a 74.0% reduction in disease incidence. In soil there was a significant reduction in FOV spores in the presence of SA NRRL B-24137. Positive correlation was also observed on different concentrations of SA NRRL B-24137 towards FOV reduction. The results of this study showed that SA NRRL B-24137 has the potential to be employed as a biocontrol agent against Fusarium cotton wilt, improving cotton growth characteristics and yield.

Saccharothrix Algeriensis NRRL B-24137 Potentiates Chemical Fungicide Carbendazim in Treating Fusarium Oxysporum f.sp. Vasinfectum-Induced Cotton Wilt Disease.

Cotton (Gossypium hirsutum) wilt is one of the destructive disease caused by Fusarium oxysporum f. sp. vasinfectum and lead to 100% yield loss under favorable conditions. This study aims to estimate the potential of biological control agents Saccharothrix algeriensis NRRL B-24137 (SA) and chemical fungicides against cotton wilt pathogen under in-vitro and in-vivo conditions. The in-vitro study revealed that carbendazim showed maximum mycelia growth inhibition with a mean of 91% over control, which was further validated in glasshouse assay. In-vitro dual culture test of biocontrol agents with F. oxysporum determined that SA had a potential to inhibit mycelia growth by 68% compared to control. Further in glasshouse assay, the combination of the SA and carbendazim (10 µg/mL) showed a significant (p < 0.05) disease control. Moreover, results demonstrated that carbendazim and SA remarkably decreased the disease development up to 83% and subsequently, significant improvement was observed in the plant growth parameters (plant length, root length, and plant weight) compared to untreated plants. Conclusively, exploration and utilization of bioagent for fungal diseases in cotton may provide a better line with maximum efficacy and with lesser adverse effects, which will pave a way toward better consequences in fungal treatments.

[Application of host induced gene silencing in crop protection against fungal diseases].

Fungal diseases are the main threat to crop yield and quality, often leading to huge economic losses. Chemical fungicides are almost useless to soil-borne and vascular fungal pathogens. The most effective way is crop resistance breeding by using resistance genes. Yet, for plants lacking resistance resources, new approaches are urgently needed for crop protection. Recently, host-induced gene silencing (HIGS) is developed based on the well-known RNA interference, and already effective against viruses and pests. However, it is challenging to validate HIGS in soil-borne fungal pathogens due to uncharacterized and complicated infection processes. Recently, we have made great progresses in revealing the infection structure of Verticillium dahliae, a soil-borne and vascular fungal pathogen that leads to verticillium wilt disease to many crops, including cotton plants. Moreover, we demonstrate that cotton exports endogenous microRNAs to inhibit virulence gene expression in V. dahliae. The most exciting achievement is the successful application of HIGS in cotton plants that confer resistance to V. dahliae. All these results reveal a promising potential for applying HIGS against a wide range of soil-borne fungi.

Tobacco Rattle Virus-Based Silencing of Enoyl-CoA Reductase Gene and Its Role in Resistance Against Cotton Wilt Disease.

A Tobacco rattle virus (TRV)-based virus-induced gene silencing assay was employed as a reverse genetic approach to study gene function in cotton (Gossypium hirsutum). This approach was used to investigate the function of the Enoyl-CoA reductase (GhECR) gene in pathogen defense. Amino acid sequence alignment of Arabidopsis ECR with homologous sequence from G. hirsutum, G. arboreum, G. herbaceum and G. barbadense showed that ECRs are highly conserved among these species. TRV-based silencing of GhECR gene in G. hirsutum induced a cell death/necrotic lesion-like phenotype. Reverse transcription polymerase chain reaction (RT-PCR) and real-time quantitative PCR showed reduced GhECR mRNA levels in TRV inoculated plants. Three isolates of Verticillium dahliae (V. dahliae) and Fusarium oxysporum f. sp. vasinfectum (FOV) were used to infect GhECR-silenced plants. Out of 6 races of 2 pathogens, down regulation of GhECR gene resulted in reduced resistance. This is the first report showing that cotton GhECR gene is involved in resistance to different strains of V. dahliae and FOV.