Effect of Soybean Cyst Nematode on Growth of Dry Bean
March 07, 2008
Berlin D. Nelson and Susilo Poromarto, Dept. Plant Pathology, NDSU
Objective: Determine the effect of soybean cyst nematode on growth of four classes of dry bean
In 2007 we established two research plots in Richland Co., North Dakota, to test the effect of soybean cyst nematode (SCN) on growth of dry bean. These experiments were established by growing dry beans in SCN infested soil in large plastic pots that were placed in the field so plants could grow under natural conditions. Soil was collected from an infested site, pasteurized to kill the SCN eggs and then placed in the plastic pots. Eggs were obtained from infested soil and were added to the soil in pots at three rates: 0 (control), 5,000 and 10,000 eggs/100 cm3 of soil. Seed was then planted and pots were buried in the soil on an infested SCN field site. There were six replications of the treatments. In one experiment we tested the pinto bean variety GTS 900 and in the other the kidney bean variety Chinook. These two dry bean types were placed in different fields. Plants were grown to maturity and plant height, pod number and weight, number of seeds in a pod, total number of seeds, weight of seeds, and total dry weight of plant was recorded. Also, the total number of cysts and eggs produced in the soil of each pot was determined.
We also established greenhouse experiments to determine the effect of SCN on dry bean growth using the same bean varieties as in the field experiments. Plants were grown in a sandy soil in 10 liter pots at five levels of SCN infestation: 0, 1,000, 5,000, 10,000 and 20,000 eggs/100 cm3 of soil. The eggs were collected in August from an infested field. There were six replications. Plants were grown to maturity and the plant growth was recorded as in the field experiments.
The field experiment with the pinto bean GTS 900 showed a significant effect of SCN on growth of the plants. All measurements of plant growth were significantly less in the SCN infested soil treatments compared to the non-infested soil. There were no significant differences between the 5,000 and 10,000 eggs/100 cm3 of soil treatments. Also, the number of cysts and eggs produced was significantly higher in the SCN infested soils compared to the control. There was some SCN reproduction on our controls due to possible contamination from the adjacent infested soil. This is the first field evidence that soybean cyst nematode can reduce the growth of dry bean and reproduce on dry bean in the field. Some of the field data is shown in Figures 1-3.
All the kidney beans at the other research site grew poorly and never developed normally. Plants were stunted and malformed. There were no significant differences in measurements of growth between treatments. We suspect based on our observations of SCN reproduction on the plant that the controls were contaminated by SCN and the nematode reproduced on the control plants. Cysts and eggs were produced on the controls, but significantly greater numbers of cysts and eggs were produced in the 5,000 and 10,000 egg treatments compared to the control. There were significantly greater cysts and eggs produced at the 10,000 egg compared to the 5,000 egg density.
The first greenhouse experiments were inconclusive since there was poor infection of the roots. We discovered that our hatching rate for the eggs was poor, apparently due to the population reverting to diapause (dormant state) during August when the eggs were collected from infested soil. We created a new population of SCN in the greenhouse and all the greenhouse experiments were repeated using eggs from this new population. The experiments are currently in progress and will run until plant maturity.
Future work will continue to refine our greenhouse testing so we know which egg densities are appropriate for testing the effects of SCN on the other 6 bean varieties that we proposed to use (Pinto bean Rally, Navy bean Vista and Navigator, Black Bean T-33 and Condor and Kidney Bean Red Hawk. Furthermore, in 2008 we will expand our field testing using methods similar to those employed in 2007.
This is the first report showing SCN can adversely effect the growth of dry bean plants and can reproduce on roots of dry bean in the field. This indicates SCN is a potential threat to dry bean production. Continued research is needed to determine the egg densities associated with yield loss.
Figure 1. Effect of soybean cyst nematode on the pinto bean variety GTS900 in a field experiment in 2007.
Figure 4. Pinto bean GTS900 growing in soil infested with soybean cyst nematode (SCN). Plant in middle is the control growing in soil without SCN. The plants on the right and left are growing in soil with 10,000 and 5,000 eggs/100 cm3 of soil, respectively. Notice the more robust plant growth of the control.