Date of Award
Master of Science
Plant and Soil Science
Macrophomina phaseolina (Tassi) Goid., is a soilborne fungus that causes charcoal rot in over 500 plant species including Zea mays L. and Glycine max (L.) Merr. The pathogen is present in most soybean growing regions of the United States. Infection in soybean can occur after emergence and throughout the vegetative growth stages in a range of environmental conditions. The syndrome is manifest during periods of hot and dry conditions during the reproductive states of the crop. Management options are lacking and consist of avoidance and irrigating crops to lessen the damage caused by the pathogen. Fluopyram is a succinate dehydrogenase inhibitor (SDHI) fungicide with a spectrum of activity against a unique and very diverse group of plant pathogens including species of Venturia, Botrytis, Alternaria, Sclerotina, Monilia and multiple species that cause powdery mildew. This fungicide also has activity against Fusarium virguliforme O’Donnell & T. Aoki, Heterodera glycines Ichinohe (soybean cyst nematode), Meloidogyne incognita acrita (root knot nematode) and other important nematode species. The objective of this research was to determine the impact of fluopyram on colonization by M. phaseolina and symptoms of charcoal rot and on plant emergence, plant height and soybean yield. A field study was initiated at the SIU Agronomy Research Station in Carbondale in 2015 and 2016. A factorial treatment structure was used with variety and fungicide treatment as the two factors. Four soybean varieties of varying maturity and three different seed treatment options. The first treatment contained a base fungicide, insecticide and a nematode biocontrol agent. The second treatment contained the base fungicide, insecticide, nematode biocontrol agent and fluopyram. The third treatment was a non-treated control. The four varieties and 3 seed treatment options were used in all possible combinations with five replications in a randomized complete block design. Each four-row plot was 3.04 m wide by 6.1 m in length with 0.76 m row spacing. The plots were infested at planting with M. phaseolina infested sorghum seed at the rate at 4.0 g of inoculum per 30.5 cm of row. Data collected included stand, plant height, seed quality and soybean yield. Soybean cyst nematode (SCN) samples were collected 2 weeks after planting. Root samples and root ratings were collected at 1 month after emergence and prior to harvest to determine colony forming units and for DNA extraction to quantify M. phaseolina in the roots using qPCR. For both growing seasons, 2015 and 2016 there was more rainfall than the 29 year average. The average air temperature was consistent with the 26 year average. There was varietal differences in qPCR for both 30 days after planting (DAP) and 120 DAP. For seed treatment options, there was not any differences between the treatments for the 30 DAP but 120 DAP showed differences. For CFU there was varietal differences but no differences between seed treatments. There was no differences between seed treatments for plant height. Seed quality was assessed in 2015. There were differences across varieties but not across seed treatment. Soybean yield differed among varieties but not seed treatment.
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