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Dissection of non-host resistance to European pear scab fungus, Venturia pirina using fluorescence phenotyping and transcriptomics

Kim Plummer: La Trobe University

<div><span>Pear scab, a major fungal disease of pears, is caused by two distinct species of host-specific <em>Venturia</em>: <em>V. nashicola</em> infects Asian pears (<em>Pyrus</em></span> x<em> bretschneideri</em><span>, <em>P. ussuriensis</em> and <em>P. pyrifolia</em></span> var. <em>culta</em><span>) and is restricted to Asia; while <em>V. pirina</em> infects European pear (<em>P. communis</em>). The incompatible interactions between European pear and <em>V. nashicola</em>, and Asian pears and <em>V. pirina</em>, are likely governed by non-host resistance. The durable nature of non-host resistance is desirable for pome fruit breeding; however, the multi-layered molecular mechanisms underlying this resistance remain poorly understood. Eurasian pears (hybrids of Asian pear</span>s crossed with European pears), with varying degrees of resistance to both pear scab fungi, provide a unique opportunity to dissect non-host resistance. Fluorescence microscopy was used to characterise compatible and incompatible phenotypes<span> of <em>V</em>. <em>pirina</em> on European, Asian, Eurasian pears and the distant non-host, apple (<em>Malus </em>x <em>domestica</em>). Comparative transcriptomics of interactions, from 3 </span>and 10 days post-inoculation (including mock inoculations), revealed the dynamic molecular mechanisms of multi-layered, non-host resistance. These data will be valuable for the development of genetic markers for scab resistance in pome fruit.</p> <p>The role of effector candidates in co-evolution of pear scab fungi with <em>Pyrus</em> spp. is also under investigation using comparative secretomics. Effector candidates may be useful in identifying durable resistance genes for molecular plant breeding, as well as biosecurity diagnostic targets for specific and sensitive detection of the Asian pear scab pathogen, <em>V. nashicola.</em></div>