Thursday, November 16, 2006 - 8:45 AM
320-4

Arbuscular Mycorrhizal Fungi Response to Flooding in Snap Bean Cultivation in South Florida.

Seema Sah, Florida International University, 11315 NW 7th St #6, Miami, FL 33172, Stewart Reed, USDA / Agricultural Research Service, 13601 Old Cutler Road, Miami, FL 33189-3388, Krishnaswamy Jayachandran, 11200 SW 8th St., Florida International University, Florida International University, Dep. of Environmental Studies, Miami, FL 33199, and Anne Hartley, Dep. of Environ. Studies, Miami, FL 33199.

Florida ranks first in the United States in snap bean production with close to 50% of the total. Flooding is a 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, nutrient uptake, and increased susceptibility to pathogens and predators. Arbuscular mycorrhizal fungi are well known to increase nutrient uptake in wet and dry conditions, and enhance secretion of growth hormones to increase plant biomass and yield. Two greenhouse experiments were conducted to determine the tolerance of snap bean to flooding at two 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 (LAI), 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. There were no significant differences in plant biomass, shoot and root carbon, and root nitrogen and phosphorus between flooded and non-flooded mycorrhizal inoculated plants. Flooding and mycorrhizal inoculations, however, significantly influenced shoot nitrogen and phosphorus. Short-term, periodic flooding initiated after colony establishment enhanced phosphorus uptake in inoculated plants. Further studies are needed to evaluate the effect of long-term flooding on snap beans.

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