Biology of Soybean Anthracnose Fungi and Their Interaction With Other Soybean Fungi (Colletotrichum, Synanamorph, Biocontrol)

122 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.Bright-field microscopy and scanning electron microscopy studies revealed that conidia of Colletotrichum truncatum and Glomerella glycines germinated terminally and subterminally with germ tubes that developed appressoria. Germ tubes were longer when on the midribs than in leaf laminae of soybean (Glycine max). Infection pegs were developed from appressoria that penetrated the epidemal cells. Discrete veinal necrosis of inoculated leaves was evident only with C. truncatum causing foliar anthracnose. Anthracnose severity was increased with increased incubation period in a mist chamber causing death of V-1 soybeans in 72 hr. Plants at V-2 to R-4 stages were all defoliated and showed stem-tip blights, but were not killed. Plants under shade showed more disease than under nonshade conditions. None of 413 soybean germplasm were immune to the disease when evaluated at V-1 stage in the mist chamber. Eighteen out of 182 field-inoculated soybean germplasm with C. truncatum gave 2% or more seeds with Colletotrichum.NaCl-yeast extract agar (SYA) was found to be selective medium for conidia, and potato-dextrose agar (PDA) for perithecia, and SYA with sucrose for both conidia and perithecia production of G. glycines. Glomerella glycines is the teleomorph of C. destructivum, not of C. truncatum. Ascospore projenies of G. cingulata isolated from soybean pod found to form loculate stromatic conidiomata on the surface of PDA and V-1 stage soybeans, and subepidermally in apple fruits upon inoculation. The loculi were without ostioles and broke open presumably from pressure exerted by developing conidia. Conidiogenesis and conidial morphology are similar to acervular synanamorph, C. gloesporioides of other ascospore projenies.Seven out of 11 saprophytes were found biologically active against soybean pathgens in dual-culture studies on PDA. Nine saprophytes were antagonistic producing zones of inhibition and inhibited growth rates of Phomopsis sojae. Soybean seeds inoculated with pathogens, C. truncatum, P. sojae, Pythium ultimum or Sclerotinia sclerotiorum, and then coated with saprophytes, Aspergillus terreus, Gliocladium roseum, Penicillium thomii or Trichoderma harzianum were increased in stand counts in both greenhouse and field experiments. The area of cotyledonary lesions caused by C. truncatum was reduced in seeds coated with G. roseum than other saprophytes.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD