|Divilov, Konstantin - University Of Illinois|
Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2016
Publication Date: 5/9/2016
Citation: Divilov, K., Walker, D.R. 2016. Reaction of Diaporthe longicolla to a strain of Sarocladium kiliense. Biocontrol Science and Technology. 26(7):938-950.
Interpretive Summary: Phomopsis seed decay of soybean, caused by the fungus Diaporthe longicolla, decreases seed quality and yield. A strain of another fungus, Acremonium strictum, which had been obtained from a contaminated D. longicolla culture that lacked a type of reproductive structure, appeared to have a deleterious effect on D. longicolla in some experiments, but not in others. Inoculation of pieces of soybean leaves for one or three days before inoculation with D. longicolla was associated with the failure of the pathogen to develop pycnidia (a type of spore-bearing reproductive structure) and a diluted extract from A. strictum inhibited growth of the pathogen, but the strain of A. strictum was not effective in suppressing growth of the pathogen in other experiments. The value of this strain of A. strictum as a biological control agent is thus unconfirmed, but further investigation of its ability to suppress soybean fungal pathogens is warranted.
Technical Abstract: Phomopsis seed decay (PSD) of soybean [Glycine max (L.) Merr.] is a seedborne fungal disease caused by Diaporthe (syn. Phomopsis) longicolla that causes yield losses and reduced seed quality. Biocontrol of this pathogen by a strain of Acremonium strictum isolated from a culture of D. longicolla was investigated in vitro, in vivo, and in ex vivo experiments with mixed results. A zone of inhibition formed between the two fungi in vitro, but it was poorly sustained, and inhibition of conidia of D. longicolla by a culture filtrate of A. strictum was not significant, though mycelia of D. longicolla were inhibited by a 25% culture filtrate of A. strictum. Co-inoculation of both fungi failed to reduce seed rot or increase seed germination in greenhouse and growth chamber experiments, respectively. Co-inoculation of both fungi also failed to reduce pycnidial development in colonies of D. longicolla growing on leaf pieces, but soaking of the leaf pieces with A. strictum spores for one or three days prior to inoculation with D. longicolla eliminated pycnidial development completely. Although it was not possible to replicate the parasitism of A. strictum on D. longicolla, the use of A. strictum as a protectant biocontrol for PSD should be further studied to evaluate its potential.