Elite Maize Germplasm: Reactions to Maize Dwarf Mosaic and Maize Chlorotic Dwarf Viruses
- R. Louie ,
- J. K. Knoke and
- W. R. Findley
Information developed on the reactions of elite maize germplasm to maize dwarf mosaic (MDMV) and maize chlorotic dwarf (MCDV) viruses should aid breeding for resistance to these pathogens. The reactions of 23 dent maize (Zea mays L.) inbreds (plus one synthetic) and 46 hybrids were evaluated in the field and greenhouse following artificial inoculation with MCDV and two strains (A and B) of MDMV. Infection, as determined by diagnostic symptoms, was higher in greenhouse than in field tests. Furthermore, most of the apparent resistance to MDMV-A in the field was not confirmed when inoculations were made on younger, more succulent plants in the greenhouse. Inbreds B68, OhlEP, Pall, Pa405, and the synthetic, OhS2, were immune or highly resistant to MDMVA and -B. Inbred B64 was only resistant to MDMV-B. No inbred was immune to MCDV, but Ga209, Oh7B, Pall, Tx601, and Oh1EP had the lowest disease incidence in the field, whereas Pall and B68 were the most resistant in the greenhouse. Most of the 32 field-planted hybrids that were resistant to MDMV-A had A632, A634, B64 or B68 as one parent; for MDMV-B, only B64 or B68 germplasm conveyed effective resistance. Hybrids B64✕B68 and B68✕B64 were immune to MDMV-A and -B in both field and greenhouse tests. The best and poorest hybrid reactions to MCDV in the field were B68✕Mol7 and A632✕B73, respectively. The most resistant hybrid (Mol7✕B64) in the greenhouse had =50% infected plants. Plant height and yield losses in inbreds and hybrids to MDMV were minimal, whereas MCDV usually caused significant height (34% average) and yield reductions (72% average). The reactions of these elite sources of germplasm to MDMV and MCDV suggest that evaluations for virus resistance in maize should include both field and greenhouse test environments.
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