Molecular and pathological identification of maize genotypes having Wsm gene governing resistance against MDMV and MCDV

Maize is seriously affected by different viruses like Maize Dwarf Mosaic Virus (MDMV) and Maize Chlorotic Dwarf Virus (MCDV) throughout the world. In Bangladesh, no genotype has been identified yet as a source of resistant gene against MDMV and MCDV. The study was carried out with the objective to screen nine maize genotypes carrying Wsm gene using three sets of Single Sequence Repeat (SSR) marker. Maize plants were inoculated with viruses. Symptoms were scored at 7, 10 and 14 dpi (days post inoculation) to calculate infection percentage and Area Under Disease Progress Curve (AUDPC). The molecular result indicated that BHM-7, BHM-5, V-92, Uttaran and Duranta carried Wsm gene, but according to pathological test, functional resistance was observed for only BHM-7, V-92 and Uttaran on the basis of infection percentage and AUDPC score. BHM-7 (BARI Hybrid Maize 7) was noticed as the best one for showing resistance against MDMV and carrying Wsm gene. No genotype was found to govern resistance against MCDV.J. Bangladesh Agril. Univ. 16(2): 208-214, August 2018

Co-infection and Disease Severity of Ohio Maize dwarf mosaic virus and Maize chlorotic dwarf virus Strains

Two major maize viruses have been reported in the United States: Maize dwarf mosaic virus (MDMV) and Maize chlorotic dwarf virus (MCDV). These viruses co-occur in regions where maize is grown, such that co-infections are likely. Co-infection of different strains of MCDV is also observed, and a synergistic enhancement of symptoms in co-infected plants was previously reported. Here, we examined the impact of co-infections of two strains of MCDV (MCDV-S and MCDV-M1, severe and mild, respectively), and co-infections of MCDV and MDMV in the sweet corn hybrid ‘Spirit’ in greenhouse experiments. Quantitative plant growth and development parameters were measured and virus accumulation was measured by reverse-transcriptase quantitative polymerase chain reaction. Virus symptoms were enhanced and plants showed no recovery over time in co-infections of MDMV-OH and MCDV-S but virus titers and quantitative growth parameters did not indicate synergy in co-infected plants. MCDV-M1 co-infections with either MDMV-OH or MCDV-S did not show symptom enhancement or evidence of synergism.

Viruses in Maize and Johnsongrass in Southern Ohio

The two major U.S. maize viruses, Maize dwarf mosaic virus (MDMV) and Maize chlorotic dwarf virus (MCDV), emerged in southern Ohio and surrounding regions in the 1960s and caused significant losses. Planting resistant varieties and changing cultural practices has dramatically reduced virus impact in subsequent decades. Current information on the distribution, diversity, and impact of known and potential U.S. maize disease-causing viruses is lacking. To assess the current reservoir of viruses present at the sites of past disease emergence, we used a combination of serological testing and next-generation RNA sequencing approaches. Here, we report enzyme-linked immunosorbent assay and RNA-Seq data from samples collected over 2 years to assess the presence of viruses in cultivated maize and an important weedy reservoir, Johnsongrass (Sorghum halepense). Results revealed a persistent reservoir of MDMV and two strains of MCDV in Ohio Johnsongrass. We identified sequences of several other grass-infecting viruses and confirmed the presence of Wheat mosaic virus in Ohio maize. Together, these results provide important data for managing virus disease in field corn and sweet corn maize crops, and identifying potential future virus threats.

Genomic of the severe isolate of Maize chlorotic dwarf virus

The complete sequences of the severe isolates of Maize chlorotic dwarf virus (MCDV-S) were obtained from cDNA clones of the viral RNA. The genome is 11 785 nucleotides (nt) in length and contains one large open reading frame between nt 455 and 10 825 that encodes a polyprotein of 3458 amino acids. Computer analysis revealed several conserved protein motifs similar to other plant picorna-like viruses. Comparison of the genome sequence of MCDV-S with that of the type strain of MCDV showed high similarities despite the difference in symptoms.