Various mycoviruses have been isolated from Sclerotinia sclerotiorum. Here, we identified a viral RNA sequence contig, representing a novel virus, Sclerotinia sclerotiorum deltaflexivirus 2 (SsDFV2), from an RNA_Seq database. We found that SsDFV2 was harbored in the hypovirulent strain, 228, which grew slowly on potato dextrose agar, produced a few sclerotia, and could not induce typical lesions on detached rapeseed (Brassica napus) leaves. Strain 228 was also infected by Botrytis porri RNA Virus 1 (BpRV1), a virus originally isolated from Botrytis porri. The genome of SsDFV2 comprised 6711 nucleotides, excluding the poly (A) tail, and contained a single large predicted open reading frame encoding a putative viral RNA replicase. Phylogenetic analysis demonstrated that SsDFV2 is closely related to viruses in the family Deltaflexiviridae; however, it also differs significantly from members of this family, suggesting that it may represent a new species. Further we determined that SsDFV2 could be efficiently transmitted to host vegetative incompatible individuals by dual culture. To our best knowledge, this is the first report that a (+) ssRNA mycovirus can overcome the transmission limitations of the vegetative incompatibility system, a phenomenon that may facilitate the potential use of mycoviruses for the control of crop fungal diseases.

As a most significant cereal crop, maize provides vital nutritional components to humans and livestock. Drought stress curtails maize growth and yield by impairing several morphological, physiological, and biochemical functions. The rising threats of drought stress significantly affect global food security and increase the ratio of hunger and starvation. The use of molecular breeding techniques has enabled maize researchers to deeply examine the genetic control of drought tolerance and the genetic differences between genotypes to drought stress. Despite the significant progress in molecular genetics, the drought tolerance mechanism is still not fully understood. With the advancements in molecular research, researchers have identified several molecular factors associated with maize tolerance to drought stress. Quantitative trait loci (QTL) mapping and genome-wide association study (GWAS) analysis have led to identifying QTL, and genes linked to drought tolerance in maize that can be further exploited for their possible breeding applications. Transcriptome and transcription factors (TFs) analysis has revealed the documentation of potential genes and protein groups that might be linked to drought tolerance and accelerate the drought breeding program. Genetic engineering has been used to develop transgenic maize cultivars that are resistant to drought stress. Clustered regularly interspaced short palindromic repeats (CRISPR/Cas9) is a new ray of hope to edit the gene of interest to enhance drought tolerance in maize and save both time and cost in cultivar development. In the current review article, we have tried to present an updated picture of the advancements of drought tolerance in maize and its future prospects. These organized pieces of information can assist future researchers in understanding the basis of drought tolerance to adopt a potential breeding tool for breeding drought-tolerant maize cultivars.

Infection by diverse mycoviruses is a common phenomenon in Sclerotinia sclerotiorum. In this study, the full genome of a single-stranded RNA mycovirus, tentatively named Hubei sclerotinia RNA virus 1 (HuSRV1), was determined in the hypovirulent strain 277 of S. sclerotiorum. The HuSRV1 genome is 4492 nucleotides (nt) long and lacks a poly (A) tail at the 3ˊ- terminus. Sequence analyses showed that the HuSRV1 genome contains four putative open reading frames (ORFs). ORF1a was presumed to encode a protein with a conserved protease domain and a transmembrane domain. This protein is 27% identical to the P2a protein encoded by the subterranean clover mottle virus. ORF1b encodes a protein containing a conserved RNA-dependent RNA polymerase (RdRp) domain, which may be translated into a fusion protein by a -1 ribosome frameshift. This protein is 45.9% identical to P2b encoded by the sowbane mosaic virus. ORF2 was found to encode a putative coat protein, which shares 23% identical to the coat protein encoded by the olive mild mosaic virus. ORF3 was presumed to encode a putative protein with an unknown function. Evolutionary relation analyses indicated that HuSRV1 is related to members within Sobemovirus, but forms a unique phylogenetic branch, suggesting that HuSRV1 represents a new member within Solemoviridae. HuSRV1 virions, approximately 30 nm in diameter, were purified from strain 277. The purified virions were successfully introduced into virulent strain Ep-1PNA367, resulting in a new hypovirulent strain, which confirmed that HuSRV1 confers hypovirulence on S. sclerotiorum.