Submitted to: New Jersey Annual Vegetable Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 7, 2005
Publication Date: January 17, 2006
Citation: Polashock, J.J., Vorsa, N. 2006. Segregating blueberry populations for mummy berry fruit rot resistance. New Jersey Annual Vegetable Meeting Proceedings. Page 199.
Mummy berry (causal agent, Monilinia vaccinii-corymbosi) is an economically important fungal disease of blueberry. There are two distinct phases of the disease. The blighting phase is initiated by ascospores produced in the ‘mummy cups’ that are deposited on and infect young leaves and flowers. A different type of spore (conidia) is then produced on the blighted tissues and is bee transferred to open flowers, initiating the start of the second phase. Spores germinate along with the pollen on the flower stigma and grow down into the ovary, thus infecting the developing fruit resulting in ‘mummies’. The second phase is often referred to as the fruit rot stage of the disease. It is this phase that we have targeted for development of resistant cultivars. Previous work demonstrated that Vaccinium darrowi, an evergreen southern blueberry species, is generally resistant to the fruit rot stage of the disease. This species was crossed with cultivated highbush blueberry (V. corymbosum) to generate populations segregating for resistance to this disease.
Blueberry flowers can be hand pollinated and infected with mummy berry conidiaspores. However, this procedure is time consuming and inefficient. As an alternative, mummy cups were produced in small pots and the ascospores produced were allowed to infect and blight susceptible blueberry varieties. The blighted plants were interspersed with flowering plants from several blueberry populations to be screened for fruit rot susceptibility in a greenhouse. Bee hives were placed in the greenhouse to facilitate pollination and transfer of fungal spores to the flowers. Mummified fruit was allowed to develop and the percent infected fruit for each plant was calculated.
Results and Conclusions
All populations tested segregated for mummy berry fruit rot resistance. Most populations showed a continuum from a low of 0% infection to over 80% infection on a given plant. There were no distinct classes in any population tested suggesting that more than one gene is involved in resistance. The most resistant clones from several populations will be genetically tested through bulk segregant analysis in an effort to isolate DNA markers for resistance. Marker assisted selection will then be used in screening breeding populations for resistant cultivar development.