|GRANKE, LEAH - Dow Agro Sciences|
|FRY, JESSICA - Michigan State University|
|HILL, THERESA - University Of California|
|ASHRATI, HAMID - North Carolina State University|
|VAN DEYNZE, ALLEN - University Of California|
|HAUSBECK, MARY - Michigan State University|
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2017
Publication Date: 12/20/2017
Citation: Naegele, R.P., Granke, L.L., Fry, J., Hill, T., Ashrati, H., Van Deynze, A., Hausbeck, M.K. 2017. Disease resistance to multiple fungal and oomycete pathogens evaluated using a recombinant inbred line population in pepper. Phytopathology. 107(12):1522-1531. https://doi.org/10.1094/PHYTO-02-17-0040-R.
Interpretive Summary: Modern pepper cultivars have good fruit quality, but are often highly susceptible to infection by viruses, bacteria, and fungi. Resistance is bred into these good quality cultivars from wild or weedy relatives that have poor fruit quality, but are resistant to pathogens. In some species of plants, "islands" of resistance genes or sites of multiple disease resistance (MDR) have been identified. These sites can allow breeders to quickly incorporate resistance to multiple pathogens into a commercially acceptable crop. We evaluated a segregating pepper population for resistance to ten different fungal pathogens, and looked for clusters of resistance genes. Genetic markers associated with resistance were detected for three of the pathogens evaluated, however none of these markers were located on the same chromosome. Based on our results, no sites of MDR were identified. However, correlations in disease incidence suggest that for at least some pathogens resistance genes are closely located or shared.
Technical Abstract: Incorporating disease resistance into cultivars is a primary focus of modern breeding programs. Resistance to pathogens is often introgressed from landrace or wild individuals with poor fruit quality into commercial-quality cultivars. Sites of multiple disease resistance (MDR) are regions or “hotspots” of the genome with closely linked genes for resistance to different pathogens, and could enable rapid incorporation of resistance. An F2-derived F6 recombinant inbred line population from a cross between Criollo de Morelos and ‘Early Jalapeno’ was evaluated in inoculated fruit studies for susceptibility to oomycete and fungal pathogens: Phytophthora capsici, P. nicotianae, Botrytis cinerea, Fusarium oxysporum, F. solani, Sclerotinia sclerotiorum, Alternaria sp., Rhizopus oryzae, R. stolonifer, and Colletotrichum acutatum. All pathogens were virulent on pepper. Significant differences in disease susceptibility were identified among lines for each of the pathogens evaluated. P. capsici was the most virulent pathogen, while Rs. oryzae and a single Sclerotinia isolate were the least virulent. Quantitative trait loci associated with resistance were identified for Alternaria, S. sclerotiorum and P. capsici. Positive correlations in disease incidence were detected between Alternaria and F. oxysporum, F. solani, and C. acutatum, as well as between C. acutatum and Botrytis, F. oxysporum, F. solani, and P. capsici. No sites of MDR were identified for the pathogens tested, however positive correlations in disease incidence were detected among pathogens suggesting there may be genetic linkage among resistance genes in CM334 and ‘Early Jalapeno’.