Current Methods of the National Cottonseed Treatment Program and Proposed Changes in Protocol

There are several pathogen isolation and/or quantification methods included in the protocol of the National Cottonseed Treatment program. Currently cooperators use a randomized experimental design block to evaluate the fungicide treatments that have been nominated for the designated growing season. Roughly 30 days after planting, cooperators collect 50 random seedlings from each location’s non-treated check plots and send them to the West Tennessee Research and Education Center for processing and evaluation. Those seedlings are split into 2 separate groups which undergo disease rating, node counts, and separate sterilization/pathogen isolation methods. According to which group they are in, seedling roots are plated on a series of selective media in an effort to quantify the pathogen populations of Thielaviopsis basicola and Pythium spp.  In addition to the plating of roots on selective media; toothpick baiting, PDA, and soil dilution plating using selective media are also utilized to further assess the pathogen populations of Rhizoctonia solani, Fusarium sp., Thielaviopsis basicola, and Pythium spp., respectively. Although the current protocol has yielded extremely useful data over the years, there are more current and updated methods for isolation and quantification of pathogens that would enhance the National Cottonseed Treatment program.  In an effort to make the sampling process more efficient, modern, and reliable, the removal of some current methods, the use of genetic confirmation, and the use of new selective media will be discussed.