Author
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Bell, Richard |
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Submitted to: HortScience
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/13/2014 Publication Date: 5/28/2015 Citation: Bell, R.L. 2015. Effect of resistant and susceptible East European pears on development and mortality of the pear psylla, Cacopsylla pyricola (Forster). HortScience. 50(5):661-665. Interpretive Summary: The pear psylla is a major pest of European pear in North America and Europe. In breeding resistant cultivars, a thorough understanding of the nature of host resistance and susceptibility is essential for designing efficient and accurate methods to identify resistant host genotypes. A developmental assay in which plants were infested with young larvae was performed on six pear varieties previously identified as highly resistant, moderately resistant or susceptible to larval feeding. One day after infestation, differences among the varieties were observed in the number of larvae feeding. Over time, more larvae died on the moderately resistant and highly resistant varieties, fewer adults developed on the moderately resistant varieties, and no adults developed on the highly resistant varieties. It was concluded that inhibition of feeding was associated with mortality, either through a lack of feeding stimulation, feeding inhibition, or due to a direct toxic effect of the resistant genotypes. ‘Bartlett’ and the wild seedling Y-167 were confirmed as susceptible, ‘Karamanlika’ and NY10352 were confirmed as moderately resistant, and Bacui-1 and Bacui-2 were confirmed as highly resistant. It was concluded that the short-term feeding antixenosis assay is predictive of long-term antibiosis and can be used as a preliminary test of resistant to aid the breeding of new pear varieties with resistant to pear psylla. Technical Abstract: The pear psylla (Cacopsylla spp.) is a major pest of European pear (Pyrus communis L.) in North America and Europe. In breeding resistant cultivars, a thorough understanding of the nature of host resistance and susceptibility is essential for designing efficient and accurate methods to identify resistant host genotypes. The study was undertaken to test the hypothesis that resistance to pear psylla consisted of the combined effects of nymphal feeding antixenosis and antibiosis, evidenced as increased mortality and delayed development, and that nymphal feeding can be used as an index for overall resistance. A developmental assay in which plants were infested with 1st instar nymphs was performed on six genotypes previously identified as highly resistant, moderately resistant or susceptible to nymphal feeding. Significant differences among the host genotypes in feeding antixenosis were exhibited at one day after infestation. Differences in antibiosis were also evident, as mortality of nymphs was greater on the resistant genotypes. There were also differences in the total number of surviving psylla and total number of adults which developed. All of these parameters were directly related to the data on feeding antixenosis. There were no significant differences among the feeding-susceptible and moderately resistant genotypes in population age structure index at day 22, reflecting the advanced stage of the few nymphs which did survive. Feeding antixenosis was associated with mortality, either through a lack of feeding stimulation, feeding inhibition, or due to a direct toxic effect of the resistant genotypes. The short-term feeding antixenosis assay is predictive of long-term antibiosis. ‘Bartlett’ and the wild seedling Y-167 were confirmed as susceptible, ‘Karamanlika’ and NY10352 were confirmed as moderately resistant, and Bacui-1 and Bacui-2 were confirmed as highly resistant. |
