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|Title:||Yield Loss Studies With Anthracnose Stalk Rot of Corn|
|Author(s):||Natti, Thomas Alexander|
|Department / Program:||Plant Pathology|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Agriculture, Plant Pathology|
|Abstract:||Twenty-four dent corn hybrids were inoculated in the first elongated stalk internode by injecting a spore suspension of Colletotrichum graminicola or Diplodia maydis to estimate potential yield loss. Experiments were done from 1978-1980 with a second location and D. maydis inoculations added in 1979 and 1980. Treatments were compared to a water injected control, as an inoculation wound effect occurred. Losses from C. graminicola ranged from 0.12.3% averaged over all hybrids and from 0-52.4% for specific hybrids. Diplodia maydis inoculations did not reduce yields. Lodging contributed more to yield loss than kernel weight reductions.
The percent of dead plants four weeks after inoculation had correlation coefficients of 0.79, 0.79 and 0.53 with yield loss from 1978, 1979 and 1980 respectively. Lodging percentage had correlation coefficients of 0.85, 0.75 and 0.53 for the same experiments. Disease severity and incidence, based on internal and external stalk discoloration respectively, had lower correlations with yield loss and in 1980 no significant correlation occurred.
Determined from weekly counts of dead plants, three disease progress variables: infection rate, area under the disease progress curve (AUDPC) and AUDPC increase of C. graminicola over the water control, had similar correlations with yield loss. Coefficients ranged from 0.82-0.72, 0.78-0.77 and 0.51-0.47 for these experiments. Yield loss prediction by linear and multiple regression showed that the percent lodging and percent dead plants three-four weeks after inoculation allowed for the highest R('2).
In 1978, natural infection by C. graminicola reduced yields 2.4% as determined by paired plant comparisons. These comparisons underestimated plot studies.
Paired plant studies showed that plants with anthracnose stalk rot (ASR) had more kernels and greater interplant stress than healthy plants. A positive correlation occurred between grain sink size and internal stalk discoloration in 1980.
In other experiments, population density affected disease assessment variables but not yield components. Lodging percentage, the percent of dead plants five-six weeks following inoculation and the incidence of ASR was affected the most by low, medium and high population densities respectively.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.
|Date Available in IDEALS:||2014-12-15|