Effect of Resistant and Susceptible East European Pears on Development and Mortality of the Pear Psylla, Cacopsylla pyricola (Förster)

Abstract

<jats:p>Pear psyllids (<jats:italic>Cacopsylla</jats:italic> spp., Hemiptera: Psyllidae) are major pests of European pear (<jats:italic>Pyrus communis</jats:italic> 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. A developmental assay was performed on six genotypes previously identified as highly resistant, moderately resistant, or susceptible to nymphal feeding. Plants were infested with first instars of <jats:italic>Cacopsylla pyricola</jats:italic> (Förster), and feeding, mortality, and larval stage were observed for 34 days. Host genotypes significantly differed in feeding antixenosis at day 1 after infestation. Differences in antibiosis were also evident, as mortality of nymphs was greater on the feeding-resistant genotypes. There were also differences in the total numbers of surviving psylla and those developing to adults. Survival was directly related to the feeding antixenosis. There were no significant differences among the feeding-susceptible and moderately resistant genotypes in population age structure, except at day 19, reflecting the advanced stage of the few nymphs that did survive. Early feeding antixenosis was associated with mortality, either through a lack of feeding stimulation, feeding inhibition, or because of a direct toxic effect of the resistant plant genotypes. The short-term feeding antixenosis assay is predictive of long-term mortality and, to a lesser extent, with delayed development. ‘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.</jats:p>

Grafting on resistant interstocks reduces scion susceptibility to pear psylla, Cacopsylla bidens

“…This combination reduced survival of psylla nymphs to 10% of that of the control. This rate of resistance can be considered moderate resistance, similar to that of the pear genotypes ‘Karamanlika’ and ‘NY10352’ . The exact mechanism of the resistance and its transfer from the interstock is not yet clear.…”

“…This rate of resistance can be considered moderate resistance, similar to that of the pear genotypes 'Karamanlika' and 'NY10352'. 18 The exact mechanism of the resistance and its transfer from the interstock is not yet clear. The fact that reduction in foliage led to lower resistance suggests that foliage is probably the source of volatile compounds essential for psylla resistance or for induction of metabolites that protect the susceptible Spadona variety from psylla.…”

“…Efforts to identify the molecular basis for resistance in these species led to the identification of quantitative trait loci (QTLs) on LG8, LG15 and LG17 in the pear genome . However, no such work has been carried out on European pears, although resistant European pear genotypes have also been found …”

“…[13][14][15] However, no such work has been carried out on European pears, although resistant European pear genotypes have also been found. [16][17][18] .…”

Differences in Gene Expression of Pear Selections Showing Leaf Curling or Leaf Reddening Symptoms Due to Pear Decline Phytoplasma

“…PD-infection of some of the original seedling trees of selections 8824-1 and 9328-1 most likely occurred by natural spread vectored by pear psylla ( Cacopsylla pyri ) Selections 8824-1 and 9328-1, which share the common ancestors of Harrow Delight, Bartlett, Old Home and Purdue 80-51, but both selections have open pollinated backgrounds meaning that the pollen sources of those pear progenitors are unknown ( Figures S1 and S2 ). Although selection 9328-1 comes from a much more diverse background than selection 8824-1, these selections appear to have both PD-tolerant (Old Home) [ 3 ] and PD-susceptible (Max Red Bartlett) [ 22 ] progenitors. The appearance of non-symptomatic trees of selections 8824-1 and 9328-1 is relatively similar, except for the higher level of red color in mature fruit of selection 8824-1 than in selection 9328-1.…”