Submitted to: American Society of Agronomy Meetings
Publication Type: Proceedings
Publication Acceptance Date: 11/12/2006
Publication Date: 11/12/2006
Citation: Sah, S.K., Reed, S.T., Jayachandran, K. 2006. Arbuscular mycorrhizal fungi response to flooding in snap bean cultivation in south Florida. American Society of Agronomy Meetings. Interpretive Summary: This research was conducted to determine the effect of flooding on arbuscular mycorrhizal (AM) fungal colonization and interactions with crop plants. Arbuscular mycorrhizae symbioses protect plants against environmental stress by enhancing nutrient uptake and growth performances, may also increase crop protection against flooding conditions. Snap bean, a major crop grown in Miami-Dade County of south Florida was used as a test plant. Any enhancement in growth of beans due to its interaction with AM fungi under flooding condition will be important to farm management system in south Florida. The main objective of this research was to determine flooding effects of AMF on snap bean and if plants benefit from the presence of AMF under short-term flooding events. A greenhouse experiment was conducted to determine the tolerance of snap beans to flooding at either an early or late vegetative growth stage. A randomized design with two different levels of flood timing and four mycorrhizal species was set up in the greenhouse. Plants were grown in steamed sand and compost in a 9:1 ratio. Flood treatments were imposed by submerging pots in tanks filled with water to 1 cm above the soil surface for eight hours every seventh day. Flood treatments began at either 13 or 20 DAP and were terminated at flowering. Plants were harvested at 30 DAP or 45 DAP for the early and late vegetative stage flood treatment, respectively. Plant height, biomass, leaf area index, mycorrhizal colonization, photosynthetic rate, transpiration rate, total carbon, total nitrogen and total phosphorus were measured. Flood timing, mycorrhizal species, and their interactions showed significant effects on root colonization. There were no significant differences in plant height, photosynthesis and transpiration rates between flooded and non-flooded plants. Flooding reduced P content in mycorrhizal plants compared to non-flooded mycorrhizal plants with the early vegetative stage flood but in the late vegetative stage flood treatment, flooding did not significantly reduced P uptake.
Technical Abstract: Florida ranks first in snap bean production in The United States with close to 50% of the total production. Flooding is one of the serious problems facing crop production in south Florida. In general, flooding creates anaerobic conditions, affects soil redox, pH and soil nutrient availability. Crop response to the flooding includes reduced stem growth, CO2 assimilation and nutrient uptake and increased susceptible to pathogens and predators. Arbuscular mycorrhizal fungi are well known to increase nutrient uptake in wet and dry conditions, and enhance secretion of growth hormone to increase plant biomass and yield. A greenhouse experiment was conducted to determine the tolerance of snap bean to flooding at different growth stages. A completely randomized design with two different levels of flooding and four levels of mycorrhizal inoculation was set up in a greenhouse. Plants were grown in a 9:1 ratio of steamed sand and compost. Flood treatments were imposed for eight hours every seventh day by emerging pots in water to 1 cm above the soil surface. Flood treatments began at either 13 or 20 days after planting (DAP) and plants were harvested 35 DAP or 45 DAP. Plant height, plant biomass, leaf area index, mycorrhizal colonization, total carbon, total nitrogen and total phosphorus were measured. Analysis of variance (ANOVA) was used to determine the differences between treatments. Experimental results revealed that short term flooding did not affect plant growth. Early flooding did not inhibit the mycorrhizal colonization. Mycorrhizal associations should form with snap bean under short-term flooding. Further studies are needed to evaluate the effect of long-term flooding on snap beans.