Palmerston North Research Center

Palmerston North, New Zealand

Palmerston North Research Center

Palmerston North, New Zealand
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Kumar S.,The New Zealand Institute for Plant and Food Research Ltd | Kirk C.,Palmerston North Research Center | Deng C.,Mount Albert Research Center | Wiedow C.,Palmerston North Research Center | And 2 more authors.
Horticulture Research | Year: 2017

Understanding of genetic diversity and marker-trait relationships in pears (Pyrus spp.) forms an important part of gene conservation and cultivar breeding. Accessions of Asian and European pear species, and interspecific hybrids were planted in a common garden experiment. Genotyping-by-sequencing (GBS) was used to genotype 214 accessions, which were also phenotyped for fruit quality traits. A combination of selection scans and association analyses were used to identify signatures of selection. Patterns of genetic diversity, population structure and introgression were also investigated. About 15 000 high-quality SNP markers were identified from the GBS data, of which 25% and 11% harboured private alleles for European and Asian species, respectively. Bayesian clustering analysis suggested negligible gene flow, resulting in highly significant population differentiation (F st =0.45) between Asian and European pears. Interspecific hybrids displayed an average of 55% and 45% introgression from their Asian and European ancestors, respectively. Phenotypic (firmness, acidity, shape and so on) variation between accessions was significantly associated with genetic differentiation. Allele frequencies at large-effect SNP loci were significantly different between genetic groups, suggesting footprints of directional selection. Selection scan analyses identified over 20 outlier SNP loci with substantial statistical support, likely to be subject to directional selection or closely linked to loci under selection.

Volz R.K.,Hawkes Bay Research Center | Kumar S.,Hawkes Bay Research Center | Chagne D.,Palmerston North Research Center | Espley R.,Mt Albert Research Center | And 2 more authors.
Acta Horticulturae | Year: 2013

The genetic relationships between 'Type 1' red flesh and several fruit quality traits in apple were assessed in breeding populations that segregated in the field for white and red flesh. Transgenic plants grown in the glasshouse and genetically modified with the MdMYB10 gene, responsible for the 'Type 1' red flesh phenotype, were also examined. Moderate positive genetic correlations were found in each of two seedling populations between the amount of red colour estimated in the cortical flesh of fruit (WCI) and astringent taste and an internal flesh browning disorder (IFBD) observed in fruit after medium-term cold storage. In one family, a quantitative trait locus for astringent taste and IFBD was mapped to the same position at the bottom of linkage group (LG) 9 as that for WCI and MdMYB10. Fruit from 'Royal Gala' trees that had been transformed with 35S-MdMYB10 had high flesh anthocyanin concentrations but also showed considerable IFBD after cold storage. In contrast, white flesh 'Royal Gala' control fruit did not show any cortical MdMYB10 expression or IFBD symptoms and had minimal flesh anthocyanin concentrations. These results are discussed with regards to future breeding strategies that aim to optimize fruit quality in 'Type 1' red flesh breeding lines.

Palmer J.,The New Zealand Institute for Plant and Food Research Ltd | Lozano L.,IRTA - Institute of Agricultural-Alimentary Research and Technology | Chagne D.,Palmerston North Research Center | Volz R.,Hawkes Bay Research Center | And 8 more authors.
Acta Horticulturae | Year: 2012

The biosynthesis of anthocyanins in many plant species is affected by environmental conditions. In apple fruit, skin anthocyanin contents are lower under hot climate conditions. We have examined anthocyanin accumulation in maturing 'Royal Gala' apples grown under temperate and hot conditions. Orchard-based apple heating to temperatures comparable to hot climates was performed and found to cause fast fruit colour loss and a reduction in anthocyanin content. Lower rates of biosynthesis are suggested, as a coordinative down-regulation of gene expression of the genes encoding the anthocyanin biosynthetic pathway occurs in hot conditions. In addition, the expression of the genes encoding the transcriptional activation complex is also reduced. Heating fruit rapidly reduced expression of apple anthocyanin-related genes, which correlated with a reduction in expression of the R2R3 MYB transcription factor (MYB10/MYB1) responsible for elevating apple colour. A genetic mapping strategy was used to identify loci associated with the expression of red skin colour under high temperatures. A population of apple seedlings was phenotyped for skin colour and anthocyanin content and then genotyped using a panel of SNP markers spanning the entire apple genome. Two markers were associated with red skin colour on linkage groups 9 and 17, including a marker located close to MYB10 (LG 9). We propose that temperature-induced down-regulation of fruit anthocyanin biosynthesis is primarily due to down-regulation of the anthocyanin regulatory complex, and that the genes encoding the complex have become useful loci for the development of marker assisted breeding of new apple cultivars tolerant of warm conditions.

Ampomah-Dwamena C.,The New Zealand Institute for Plant and Food Research Ltd | Dejnoprat S.,The New Zealand Institute for Plant and Food Research Ltd | Lewis D.,Palmerston North Research Center | Sutherland P.,The New Zealand Institute for Plant and Food Research Ltd | And 3 more authors.
Journal of Experimental Botany | Year: 2012

Carotenoid accumulation confers distinct colouration to plant tissues, with effects on plant response to light and as well as health benefits for consumers of plant products. The carotenoid pathway is controlled by flux of metabolites, rate-limiting enzyme steps, feed-back inhibition, and the strength of sink organelles, the plastids, in the cell. In apple (Malus × domestica Borkh), fruit carotenoid concentrations are low in comparison with those in other fruit species. The apple fruit flesh, in particular, begins development with high amounts of chlorophylls and carotenoids, but in all commercial cultivars a large proportion of this is lost by fruit maturity. To understand the control of carotenoid concentrations in apple fruit, metabolic and gene expression analysis of the carotenoid pathway were measured in genotypes with varying flesh and skin colour. Considerable variation in both carotenoid concentrations and compound profile was observed between tissues and genotypes, with carotenes and xanthophylls being found only in fruit accumulating high carotenoid concentrations. The study identified potential rate-limiting steps in carotenogenesis, which suggested that the expression of ZISO, CRTISO, and LCY-ε, in particular, were significant in predicting final carotenoid accumulation in mature apple fruit. © 2012 The Authors.

Henry-Kirk R.A.,The New Zealand Institute for Plant and Food Research Ltd | McGhie T.K.,Palmerston North Research Center | Andre C.M.,The New Zealand Institute for Plant and Food Research Ltd | Hellens R.P.,The New Zealand Institute for Plant and Food Research Ltd | And 2 more authors.
Journal of Experimental Botany | Year: 2012

Proanthocyanidins (PAs) are products of the flavonoid pathway, which also leads to the production of anthocyanins and flavonols. Many flavonoids have antioxidant properties and may have beneficial effects for human health. PAs are found in the seeds and fruits of many plants. In apple fruit (Malus × domestica Borkh.), the flavonoid biosynthetic pathway is most active in the skin, with the flavan-3-ols, catechin, and epicatechin acting as the initiating units for the synthesis of PA polymers. This study examined the genes involved in the production of PAs in three apple cultivars: two heritage apple cultivars, Hetlina and Devonshire Quarrenden, and a commercial cultivar, Royal Gala. HPLC analysis shows that tree-ripe fruit from Hetlina and Devonshire Quarrenden had a higher phenolic content than Royal Gala. Epicatechin and catechin biosynthesis is under the control of the biosynthetic enzymes anthocyanidin reductase (ANR) and leucoanthocyanidin reductase (LAR1), respectively. Counter-intuitively, real-time quantitative PCR analysis showed that the expression levels of Royal Gala LAR1 and ANR were significantly higher than those of both Devonshire Quarrenden and Hetlina. This suggests that a compensatory feedback mechanism may be active, whereby low concentrations of PAs may induce higher expression of gene transcripts. Further investigation is required into the regulation of these key enzymes in apple. © 2012 The Author.

Kumar S.,The New Zealand Institute for Plant and Food Research Ltd | Rowan D.,Palmerston North Research Center | Hunt M.,Palmerston North Research Center | Chagne D.,Palmerston North Research Center | And 2 more authors.
Molecular Breeding | Year: 2015

Flavour is an important food trait, yet little is known about the genetic architecture and mode of inheritance of apple flavour compounds. The objectives of this study were to: understand the inheritance of flavour volatiles in a clonally replicated germplasm population; unravel correlation networks of volatiles; and to use genome-wide single nucleotide polymorphism (SNP) markers to identify genomic regions that play a role in the expression of flavour volatiles. This analysis revealed that more than half of the 37 volatiles (measured by gas chromatography–mass spectrometry) showed high heritability (h2 > 0.4), with only a small number (3 of the 37) displaying low heritability (h2 < 0.2). Majority (~85 %) of the significant SNP loci displayed the additive mode of inheritance. Our results supported the roles of MdAAT, MdCXE and MdLOX genes in the expression of apple flavour volatiles. Effect sizes of SNP loci, some of which are associated with multiple compounds, were small (<10 %), which is consistent with a polygenic quantitative inheritance model. New genomic locations associated with multiple flavour compounds were found, and some SNPs were associated with both sensory flavour and some flavour volatiles. Simultaneous genome-wide association study for sensory flavour and flavour compounds is recommended for unravelling genetic mechanisms to facilitate marker-assisted breeding for targeted flavours. © 2015, Springer Science+Business Media Dordrecht.

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