Submitted to: HortScience
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/28/2006
Publication Date: 6/30/2006
Citation: Sah, S., Reed, S.T., Jayachandran, K., Dunn, C.B. 2006. The effect of repeated short-term flooding on mycorrhizal survival in snap bean (phaseolus vulgaris l.) roots. HortScience. 41(3):598-602. Interpretive Summary: Arbuscular-mycorrhizal (AM) fungi are beneficial fungi that live in the roots of most vascular plants. The plant supplies carbon for the fungal growth and in turn the AM enhances the uptake of relatively immobile nutrients such as phosphorus, sulfur, copper, zinc, and boron. . Because they are aerobic mycorrhizal plant root symbiosis was not considered significant under flooded conditions. However, AM colonization of wetland plants is now believed more common than previously thought. In the humid tropics of North and Central America, vegetable crops can be planted in September to take advantage of the Fall rainy season. Heavy thunderstorms that saturate the soil and result in standing water for 24 hours or less are common. Short-term floods, especially on sandy soils, may leach banded fertilizer reducing plant fertilizer uptake efficiency. Because mycorrhizae were not thought of as effective under waterlogged conditions, seeds planted in flood prone areas are not enhanced with mycorrhizal mixes. However, mycorrhizal associations tolerant to wet conditions might help improve nutrient uptake after a flood.
Technical Abstract: Since arbuscular-mycorrhizal (AM) fungi are aerobic, symbiosis was not considered significant under flooded conditions. However, AM colonization of wetland plants is now believed more common than previously thought. In the humid tropics, storms that result in standing water for 24 h or less are common. Short-term floods, especially on sandy soils, may leach banded fertilizer, reducing uptake efficiency. Crops planted in flood prone areas are not normally enhanced with mycorrhizal mixes. However, mycorrhizal associations tolerant to wet conditions may improve nutrient uptake as plants recover from short-term flooding. Greenhouse studies were initiated to determine the effects of frequent short-term floods on mycorrhizal colonization and subsequent development in snap bean (Phaseolus vulgaris L.) plants. Flooding reduced soil O2 content and leaf photosynthesis for 24 h, however, flooding produced no obvious long-term physical effects on plant shoots. After the initial infection, flooding did not affect survival of existent colonies. Percent root colonization in flooded vs. non-flooded treatments was not significantly different at either 31 or 50 DAP. As root length increased there was a concomitant increase in colonization so that percent colonization remained approximately the same in both flooded and non-flooded treatments. In the second study, three weekly floods beginning 13 DAP (7 days after plant emergence) did not inhibit initial mycorrhizal colonization. Mycorrhizal associations should form with snap bean under conditions subject to short-term flooding. Additional research is needed to determine the efficacy of different mycorrhizal mixes under short-term flooded conditions in the field.