Developing Methods for Determining Survival of Phytophthora capsici in Soil for Establishing Effective Cropping Rotations for Sustainable Vegetable Production
This study was conducted to develop a reliable procedure by combining a sieving-centrifugation method and real-time quantitative polymerase chain reaction (QPCR) to quantify Phytophthora capsici oospores in soil. The relationship between number of oospores recovered from soil and number of oospores incorporated into the soil was Ŷ = -0.95 + 1.31X – 0.03X2 (R2 = 0.98), where Ŷ = log10 of number of oospores recovered from soil and X = log10 of number of oospores incorporated into soil. The relationship between the DNA quantities and number of oospores of P. capsici was Ŷ = -3.57 -0.54X +0.30X2 (R2 = 0.93), where Ŷ = log10 (ng of P. capsici DNA) and X = log10 (number of oospores).
Short-term outcomes of this research were to develop of reliable method for detection and quantification of Phytophthora capsici in soil. Intermediate- and long-term outcomes of this study were to determining survival of P. capsici in soil, establishing effective cropping rotations, reducing use of pesticides, establishing effective strategies for management of one of the most destructive diseases of vegetables, and increasing profitability of vegetable production; thus, establishing sustainable vegetable production in the North Central region.
In this study a reliable method for extraction and enumeration of oospores of P. capsici in soil was developed. Also, a molecular method was developed to identify oospores of P. capsici from oospores of other Phytophthora and oomycete species.
Impacts and Contributions/Outcomes
Illinois grows about 20,000 acres of pumpkin and 10,000 acres of cucumbers, eggplants, cantaloupe, peppers, squash, tomatoes, and watermelons. More than 90% of commercial processing pumpkins are produced and processed in Illinois. Also, the North Central region produces more than 130,000 acres of these crops. Phytophthora blight, caused by P. capsici, is a serious threat to production of these crops in the regions as well as nationwide. At present, there is no long-term sustainable solution for management of this disease. A combination of cultural practices, including seed-treatment, field scouting, fungicide application, and irrigation management, are used to minimize the damages caused by P. capsici to vegetable crops. Effective cropping rotations are the most sustainable approach to manage P. capsici in soil. In this research, a reliable method was developed to quantify oospores (surviving bodies) of P. capsici in soil. A 5-year experiment is being conducted to determine survival of P. capsici oospores. Survival of the oospores is tested every six months. Host range of P. capsici has already been determined. Consequently, effective cropping rotations for sustainable management of Phytophthora blight of vegetables will be available in the near future (after determining maximum survival of oospores in soil. Effective cropping rotation is the cheapest and safest method for managing P. capsici.