Survival and seed transmission of Fusarium moniliforme, Fusarium proliferatum, and Fusarium subglutinans in maize
Date
1996
Authors
Cotten, Teresa Kay
Major Professor
Advisor
Munkvold, Gary P.
Committee Member
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Abstract
The roles of residue size and burial depth were assessed in the survival of Fusarium moniliforme, F. proliferatum, and F. subglutinans in inoculated maize stalk residue. Stalk pieces (small or large sizes) were soaked in a spore suspension of F. moniliforme, F. proliferatum, or F. subglutinans and placed on the field soil surface or buried at 15 or 30 cm. Residue pieces were recovered periodically, cultured on a selective medium, and microscopically examined for the presence of the inoculant Fusarium species. After 21 months, Fusarium species were recovered from 0-50% of inoculated stalk pieces in a long-term, continuous maize field, from 0-28% of inoculated stalk pieces placed in a maize/soybean/oat rotation field, and from 0-25% of noninoculated stalk pieces at both locations. Residue size and residue depth were significant, and the strain x time and depth x time interactions were significant. However, there were also significant interactions among time, strain and depth at one location. After 12 months, Fusarium recovery was generally higher from buried residues, but after 21 months, recovery was generally higher from surface residues. Linear regression slopes for fungus survival in the surface residues over time were less steep than those for survival in buried residues. Coefficients of determination ranged from 0.35 to 0.82 for the surface residues, and 0.81 to 0.98 for the buried residues. Decline in survival over time followed a linear pattern in buried residues, but not in surface residues. Vegetative compatibility tests confirmed that F. moniliforme, F. proliferatum, F. subglutinans strains can survive at least 21 months in surface or buried maize residue. Results showed that maize residue can act as a long-term source of inoculum for Fusarium infection of maize plants.
Seeds of inbred maize line LH82, infested with one of six (1995) or nine (1996) Gibberel/a fujikuroi anamorph strains (Fusarium moniliforme [mating population A], F. proliferatum [mating pop. D], or F. subglutinans [mating pop. El), were planted in field plots near Ames, Iowa. Plant samples were taken at V3, V10, R3 and harvest maturity. Recovered Fusarium strains were paired with the respective inoculants in vegetative compatibility tests. The inoculated Fusarium strains were isolated from the crowns, mesocotyls, third nodes, sixth nodes, ear shoots, ear shanks and kernels. lnoculant strains were recovered from 45-90% of plants at growth stage V3, 0-40% of V1 0 plants, 30-44% of plants sampled at stage R3, and 10-30% of maize ears sampled at maturity. lnoculant strains infected 0.5-3.3% of the kernels at maturity. Seed transmission and systemic infection by the F. subglutinans strains was less frequent than with the F. moniliforme or F. proliferatum strains. Vegetatively compatible isolates were not recovered from the noninoculated controls until after pollination. Results showed that strains of F. moniliforme, F. proliferatum, and F. subglutinans can grow systemically in maize plants and can be transmitted through asymptomatic seed.
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