Reproduction of Soybean Cyst Nematode on Dry Bean Cultivars Over Multiple Generations.

Phaseolus vulgaris is a host of soybean cyst nematode (SCN; Heterodera glycines), a pathogen recently introduced into the major dry bean production area of North Dakota and northern Minnesota. The nematode reproduces less on most bean classes compared with soybean but can reduce plant growth and seed yield. An important question is the following: will SCN adapt to dry bean and, over time, increase in ability to reproduce on roots? To answer this question, the following experiments were conducted with cultivars from three bean classes. The cultivars 'Premiere' and 'Cirrus' (navy), 'Buster' and 'Othello' (pinto), and 'Eclipse' and 'Jaguar' (black) were grown in "Cone-tainers" in sand in plastic pots immersed in a water bath at 27°C in the greenhouse. Seedlings were inoculated with 2,000 eggs per plant of SCN HG 0 and cysts were harvested and counted after 40 days. The eggs were immediately extracted from those cysts and seedlings were inoculated again and grown for 40 days using the same methods. Soybean 'Lee 74' was used as a control. A female index (number of cysts produced on the test plant divided by the number of cysts produced on Lee 74) was calculated for each bean cultivar after each period of 40 days. This procedure was repeated until eight generations of eggs were completed and then the experiment was repeated. There was no significant (P ≤ 0.05) change over time in the female index on the six bean cultivars. Therefore, there was no evidence that SCN HG 0 was increasing reproduction on dry bean cultivars during two 11-month periods of continual reproduction of HG 0 on roots.