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|Title:||Epidemiology of Phomopsis Seed Decay of Soybeans: Infection Progress and the Effects of Weather and Host Resistance|
|Author(s):||Shortt, Barry James|
|Department / Program:||Plant Pathology|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Agriculture, Plant Pathology|
|Abstract:||Phomopsis seed decay of soybeans (Glycine max L.), caused by the fungi Diaporthe phaseolorum (Cke. & Ell.) Sacc. var. sojae Wehm. and an unidentified Phomopsis sp., reduces the germination, vigor, and quality of seeds grown in seasons with warm, wet weather near harvest. The establishment of Phomopsis sp. in six soybean cultivars was measured in natural field epidemics in east-central Illinois in 1980 and 1981. Infection incidences in surface disinfested plant parts were estimated by recovery of the pathogen on potato-dextrose agar. Infection progress curves for the period between emergence and harvest were analyzed using the Weibull cumulative distribution function, and were related to weather using multiple linear regression.
Plant infection increased faster, and seed decay was greater in 1981 than in 1980, primarily because of wetter weather. Shapes of the infection progress curves differed between years, and to a lesser extent, between plant parts. The incidences of infected stem pieces, pod halves, and seeds were not closely related, although all were greater in 1981. Seed decay was low in 1980, but in 1981 ranged from 0.5% in Elf to 26% in Wells. Resistance to seed decay, also expressed as low seed infection, apparently did not involve resistance to stem or pod infection. Stem and pod infection were affected by rainfall, dew, and humidity. Seed infection was affected by host resistance, stage of development, and humidity and temperature. Seed decay was greatest in the maturity group II cultivars, but an infection assay of pods and seeds in vitro detected little difference between maturity groups.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.
|Date Available in IDEALS:||2014-12-15|