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Kerikeri, New Zealand

Nardozza S.,The New Zealand Institute for Plant and Food Research Ltd | Boldingh H.,Ruakura Research Center | Richardson A.,Kerikeri Research Center | Walter M.,Motueka Resarch Center | And 4 more authors.
Acta Horticulturae | Year: 2015

Pseudomonas syringae pv. Actinidiae (Psa) biovar 3 (also known as Psa-V) is a devastating bacterial pathogen of kiwifruit vines, and the causal agent of bacterial canker. The disease causes symptoms ranging from leaf spotting to woody cankers that produce exudate. Several Pseudomonas syringae pathovars are able to colonise distant plant tissues by systemic movement within the host. Published studies of kiwifruit Psa suggest bacteria may spread systemically through xylem vessels. The aim of this work is to understand how xylem sap composition, and therefore nutrient availability, can affect the ability of Psa biovar 3 to proliferate in xylem. We have examined the composition of the xylem saps of different kiwifruit cultivars throughout the season at three sites in New Zealand and using in vitro growth studies, tested the ability of a virulent Psa biovar 3 strain to proliferate on these xylem sap samples. Our results show that xylem sap metabolite profiles change both during the season and between cultivars. In vitro Psa growth in xylem sap was dependent on the plant phenological stage and cultivar. This information will be used to develop management practices to manipulate Psa-host interactions and to select more tolerant cultivars. Source


Nardozza S.,The New Zealand Institute for Plant and Food Research Ltd | Boldingh H.L..,Ruakura Research Center | Osorio S.,Max Planck Institute of Molecular Plant Physiology | Hohne M.,Max Planck Institute of Molecular Plant Physiology | And 8 more authors.
Journal of Experimental Botany | Year: 2013

Tomato, melon, grape, peach, and strawberry primarily accumulate soluble sugars during fruit development. In contrast, kiwifruit (Actinidia Lindl. spp.) and banana store a large amount of starch that is released as soluble sugars only after the fruit has reached maturity. By integrating metabolites measured by gas chromatography-mass spectrometry, enzyme activities measured by a robot-based platform, and transcript data sets during fruit development of Actinidia deliciosa genotypes contrasting in starch concentration and size, this study identified the metabolic changes occurring during kiwifruit development, including the metabolic hallmarks of starch accumulation and turnover. At cell division, a rise in glucose (Glc) concentration was associated with neutral invertase (NI) activity, and the decline of both Glc and NI activity defined the transition to the cell expansion and starch accumulation phase. The high transcript levels of β-amylase 9 (BAM9) during cell division, prior to net starch accumulation, and the correlation between sucrose phosphate synthase (SPS) activity and sucrose suggest the occurrence of sucrose cycling and starch turnover. ADP-Glc pyrophosphorylase (AGPase) is identified as a key enzyme for starch accumulation in kiwifruit berries, as high-starch genotypes had 2- to 5-fold higher AGPase activity, which was maintained over a longer period of time and was also associated with enhanced and extended transcription of the AGPase large subunit 4 (APL4). The data also revealed that SPS and galactinol might affect kiwifruit starch accumulation, and suggest that phloem unloading into kiwifruit is symplastic. These results are relevant to the genetic improvement of quality traits such as sweetness and sugar/acid balance in a range of fruit species. © The Author 2013. Source


Nardozza S.,The New Zealand Institute for Plant and Food Research Ltd | Kashuba P.,Kerikeri Research Center | McCaughan L.,Kerikeri Research Center | Philippe M.,The New Zealand Institute for Plant and Food Research Ltd | And 4 more authors.
Scientia Horticulturae | Year: 2015

Red-fleshed Actinidia chinensis fruit are new to the market and consumers' acceptance of these kiwifruit is subject to the development of a consistent red flesh pigmentation. We hypothesised that differences in the availability of source carbohydrate have an effect on the variation in fruit red colour within an orchard. In a block-red-fleshed (red colour in the inner and outer pericarp) genotype, effects of shoot types, parent cane types, vine rootstock, fruit position on the shoot, flowering time and light exposure on fruit flesh colour were evaluated. Vine vigour had a consistent effect on the outer pericarp colour of fruit. Fruit from the vines on the more vigorous rootstock (A. deliciosa 'Bruno' seedling) had the most intense and least variable outer pericarp red colour. In addition, fruit from long shoots on small diameter canes (10-15. mm) were also the most intensely pigmented, whilst fruit position on the shoot, flowering time and fruit light exposure did not affect fruit flesh red colour. The vigour of vines due to rootstock, cane and shoot size also affected fruit growth and dry matter accumulation. These results suggest that, similarly to fruit growth (i.e. fresh weight and dry matter), vine vigour, carbohydrate availability and competition for resources between fruit and vegetative shoot growth have a putative role in red colour development in kiwifruit flesh. These finding can be used to develop optimised growing systems for new red-fleshed kiwifruit cultivars that minimise excessive shoot vigour to enhance red pigmentation of fruit flesh. © 2015 Elsevier B.V.. Source

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