Project Number: 2090-21000-032-03-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jun 26, 2016
End Date: Mar 21, 2018
(1 Assess Downy mildew (Phytophthora phaseoli) of lima bean. (2) Assess Pod rot (Phytophthora capsici) of lima bean.
Hypocotyl screens for P. phaseoli resistance testing will be conducted on each accession of the diversity panel using each of races E and F. Field inoculations using P. phaseoli will be conducted on each accession of the diversity panel. Each accession will be grown in replicates in late spring and inoculated and rated for disease in late summer (inoculations and ratings usually conducted in late August). There will be two separate field trials, one for race E (Newark, DE) and one for race F (Georgetown, DE), following our standard methods. 1- Pod Assay: Screening for P. capsici resistance will be conducted on each accession of the diversity panel using three different field-sourced isolates from the MAR. Performing pod assays allows us to test isolates with differing characteristics, already in-hand, such as mefanoxam sensitivity, mating type, and virulence on a panel of eight widely used lima bean cultivars. While all are virulent, we will select differing levels of mefanoxam resistance, from different grower fields in the MAR. a. Rejuvenation and multiplication of isolates onto sterile media. (April-May) b. Each accession of the diversity panel will be grown in the greenhouse and allowed to form pods. (This stage of the experiment will need to be conducted in two stages due to space limitation and also the need for different photoperiods to allow for flowering of some of the temperate accessions). (May-June/June-July) c. Inoculation will be conducted on harvested surface sterilized lima bean pods using an agar plug containing the growing P. capsici organism. Disease rating will be conducted and data collected. (June-July) Disease ratings will be +/- with a detailed description of symptoms and disease progress. Whole plant assay: Lima bean diversity panel accessions will be screened for resistance/susceptibility to P. capsici. Inoculations will be conducted at the University of Delaware’s Fischer greenhouse in our mist growth chambers using only one isolate due to space limitations of using whole plants. This isolate will be selected based on the most yield reducing and mefanoxam insensitive isolate, as this bears the highest risk to the region.