Host-Parasite Interactions of the Soybean Cyst Nematode and Snap Beans Compared to Soybeans (Phaseolus Vulgaris, Heterodera Glycines, Max, Resistance, Temperature)
Soybean cyst nematode (SCN), (Heterodera glycines), a devastating parasite of soybean (Glycine max), was recently reported as damaging snap bean (Phaseolus vulgaris) in an Illinois commercial snap bean field. Because little information concerning the host-parasite relations of snap bean and SCN exists, studies were conducted to: (1) discover sources of resistance in snap bean to SCN, (2) determine effects of temperature on SCN in resistant and susceptible snap beans and soybeans, and (3) to determine pathogenicity of the SCN on snap bean. This study was divided into 3 sections. The first series of experiments was designed as a randomized complete block in the greenhouse to screen snap bean lines for host suitability and resistance against two populations of SCN. The second section was designed as a 5 x 4 x 10 factorial representing 5 temperatures, 4 host genotypes (resistant and susceptible snap beans and resistant and susceptible soybeans), and 10 sampling times to investigate these effects on the nematode development and plant response. Thirdly, one experiment was designed as a randomized complete block in the greenhouse with 5 inoculation treatments on 2 snap bean genotypes to compare the pathogenicity of SCN on snap bean to that on soybean. Several snap bean cultivars were demonstrated to be equally suitable hosts as the susceptible soybean control, whereas WIS (RRR) 36 breeding line was resistant to both populations. Temperature and host genotype had a profound effect on the nematode developmental rate. At 28 C development was most rapid, closely followed by 20 and 24 C. At 20, 24 and 28 C the most nematodes reached maturity. An equation was generated from the data to predict the developmental stage based on time and temperature variables. Male:female ratios were higher for snap beans than soybeans and higher for Eagle snap bean than any other genotype. Although necrotic responses (hypersensitive reactions) to SCN were observed in all four genotypes, the resistant soybean produced more necrotic responses than the resistant snap bean, which produced more than the susceptible soybean and snap bean. Temperature had no effect on the response. Pathogenicity of SCN was not proved on snap bean cvs. Eagle and Goldenrod.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign