Motueka, New Zealand
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Chagne D.,The New Zealand Institute for Plant and Food Research Ltd | Crowhurst R.N.,Mount Albert Research Center | Pindo M.,Instituto Agrario San Michele allAdige Research and Innovation Center | Thrimawithana A.,Mount Albert Research Center | And 39 more authors.
PLoS ONE | Year: 2014

We present a draft assembly of the genome of European pear (Pyrus communis) 'Bartlett'. Our assembly was developed employing second generation sequencing technology (Roche 454), from single-end, 2 kb, and 7 kb insert paired-end reads using Newbler (version 2.7). It contains 142,083 scaffolds greater than 499 bases (maximum scaffold length of 1.2 Mb) and covers a total of 577.3 Mb, representing most of the expected 600 Mb Pyrus genome. A total of 829,823 putative single nucleotide polymorphisms (SNPs) were detected using re-sequencing of 'Louise Bonne de Jersey' and 'Old Home'. A total of 2,279 genetically mapped SNP markers anchor 171 Mb of the assembled genome. Ab initio gene prediction combined with prediction based on homology searching detected 43,419 putative gene models. Of these, 1219 proteins (556 clusters) are unique to European pear compared to 12 other sequenced plant genomes. Analysis of the expansin gene family provided an example of the quality of the gene prediction and an insight into the relationships among one class of cell wall related genes that control fruit softening in both European pear and apple (Malusxdomestica). The 'Bartlett' genome assembly v1.0 ( pyrus-communis/genome-v1.0) is an invaluable tool for identifying the genetic control of key horticultural traits in pear and will enable the wide application of marker-assisted and genomic selection that will enhance the speed and efficiency of pear cultivar development. © 2014 Chagné et al.

Bus V.,Hawkes Bay Research Center | Brewer L.,Motueka Research Center | Morgan C.,Motueka Research Center
Acta Horticulturae | Year: 2013

Scab is a major disease of pear worldwide. The disease is caused by two species: Venturia pirina, which infects European pear, and V. nashicola, which infects Asian pear species. The host types are mutually exclusive to the Venturia species and this phenomenon is heavily exploited in the Plant & Food Research pear breeding programme for the breeding of scab-resistant pear cultivars. In 2008 and 2009, 18 seedling families with a range of 0 to 100% Asian pear pedigree were screened in the glasshouse following artificial inoculation with V. pirina, the scab species present in New Zealand. The progenies showed a range of resistance reactions, mostly in the classes 0 (no symptoms) and 2 (necrotic reaction without sporulation). Some seedlings showed a hypersensitive response (class 1) or chlorotic reactions with limited sporulation (class 3). As expected, the seedling progenies of low Asian pear descent showed high proportions (78-91%) of susceptible seedlings. Ten families showed 100% resistant seedlings, with a further two families showing 98 and 94% resistance. We show that the average proportion of Asian ancestry of a progeny estimated from their parents is not necessarily a good predictor for the expected resistance segregations of that progeny.

Knabel M.,The New Zealand Institute for Plant and Food Research Ltd | Knabel M.,University of Auckland | Friend A.P.,Motueka Research Center | Palmer J.W.,Motueka Research Center | And 10 more authors.
BMC Plant Biology | Year: 2015

Background: The vigour and precocity of trees highly influences their efficiency in commercial production. In apple, dwarfing rootstocks allow high-density plantings while their precocious flowering enables earlier fruit production. Currently, there is a lack of pear (Pyrus communis L.) rootstocks that are equivalent to the high yielding apple rootstock 'M9'. For the efficient breeding of new Pyrus rootstocks it is crucial to understand the genetic determinants of vigour control and precocity. In this study we used quantitative trait loci (QTLs) analysis to identify genetic loci associated with the desired traits, using a segregating population of 405 F1 P. communis seedlings from a cross between 'Old Home' and 'Louise Bonne de Jersey' (OHxLBJ). The seedlings were grafted as rootstocks with 'Doyenne du Comice' scions and comprehensively phenotyped over four growing seasons for traits related to tree architecture and flowering, in order to describe the growth of the scions. Results: A high density single nucleotide polymorphism (SNP)-based genetic map comprising 597 polymorphic pear and 113 apple markers enabled the detection of QTLs influencing expression of scion vigour and precocity located on linkage groups (LG)5 and LG6 of 'Old Home'. The LG5 QTL maps to a position that is syntenic to the apple 'Malling 9' ('M9') Dw1 locus at the upper end of LG5. An allele of a simple sequence repeat (SSR) associated with apple Dw1 segregated with dwarfing and precocity in pear and was identified in other pear germplasm accessions. The orthology of the vigour-controlling LG5 QTL between apple and pear raises the possibility that the dwarfing locus Dw1 arose before the divergence of apple and pear, and might therefore be present in other Rosaceae species. Conclusion: We report the first QTLs associated with vigour control and flowering traits in pear rootstocks. Orthologous loci were found to control scion growth and precocity in apple and pear rootstocks. The application of our results may assist in the breeding process of a pear rootstock that confers both vigour control and precocity to the grafted scion cultivar. © 2015 Knäbel et al.

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