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    Hypobaric treatment : an innovative approach to control postharvest diseases of strawberries : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 2014) Hashmi, Majid Suhail
    Fungal decay is one of the major causes of postharvest losses in strawberries. Conventionally fungicides have been used to control fungal decay. However, fungicides have been questioned as a sustainable and safe method. Pre-storage application of short-term hypobaric treatment is one of the potential non-chemical methods for reducing fungal decay. In this study efficacy of postharvest hypobaric treatments to control natural rot development in strawberries was evaluated and analysed for the possible induction of resistance. Treatment of strawberries with hypobaric pressure (50 kPaa for 4 h at 20 °C) consistently reduced rot development in subsequent storage at 20 or 5 °C. An in vitro study found that the rate of radial growth of colonies of Botrytis cinerea and Rhizopus stolonifer was unaffected by hypobaric treatment. Moreover, post-hypobaric treated strawberries inoculated immediately or 12 h after treatment with corresponding fungi led to significant (P< 0.05) rot reduction during storage at 20 °C. Bio-chemical analysis of strawberries suggested that hypobaric treatment upregulated the activities of defence-related enzymes with phenylalanine ammonia-lyase (PAL) and chitinase peaking 12 h after treatment, while peroxidase (POD) increased immediately after treatment. These results provide evidence that the mechanism of action of hypobaric treatment is induction of the defence system within the fruit rather than a direct effect on fungal viability. Furthermore, the 4 h delay in cooling required for hypobaric treatment did not cause greater rots compared to immediate cooling at-harvest. Therefore treatment is recommended to be applied at low temperature immediately after harvest. Despite these scientific results, a combination of hypobaric treatment and cold storage may not be sufficient for extending commercial storage life of strawberries. For more effective application, probably hypobaric treatment should be regarded as a hurdle technology to be used in conjunction with other physical treatments such as (UV-C, heat and ultrasound) and/or volatile chemical treatments.
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    Comparative genome mapping of the Rosaceae : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Plant Molecular Genetics and Genomics, Institute of Molecular BioSciences, Massey University, Palmerston North, New Zealand
    (Massey University, 2012) Bushakra, Jill M
    Comparative genome mapping uses genetic map and DNA sequence alignment to assess genome conservation between two or more organisms. This study makes use of the recent genome sequence availability of four Rosaceae genera, and the development of new, and the expansion of existing, linkage maps to: 1) explore overall genome synteny between apple and strawberry; 2) assess homology between, and the degree of ancestral genome rearrangement among, four genera; and 3) compare genome synteny with respect to the production of anthocyanins between raspberry and strawberry. The inter-tribal comparison of the genomes of apple and diploid strawberry, conducted by adding 56 newly developed orthologous markers to existing linkage maps, identified 21 regions of genomic synteny between the linkage groups of apple and strawberry. In addition, this work identified two each of potential translocations, inversions and insertions, and provided a set of orthologous markers that will be useful for orienting and anchoring other Rosaceae genome sequences. Orthologous- and other DNA sequence-based markers were used in the construction of new linkage maps for Rubus occidentalis 96395S1 and R. idaeus =Latham‘. The sequences from which the Rubus markers were designed were compared with the draft genome sequences of Malus × domestica =Golden Delicious‘, Fragaria vesca =Hawaii 4‘, and Prunus persica =Lovell‘ to identify regions of orthology. This first comparison of Rubus linkage maps with other members of the Rosaceae identified a nearly 1:1 homology between the linkage groups of Rubus and F. vesca, as well as family-wide conservation among some linkage groups. The F1 progeny of Rubus occidentalis 96395S1 × R. idaeus =Latham‘ was used to conduct a quantitative trait locus (QTL) analysis to explore the presence of associations between genotype and the variation in concentrations of anthocyanins in the fruit. Seven associations of traits with markers designed from the sequences of transcription factors and anthocyanin biosynthetic pathway genes were identified, providing opportunities for further fine-scale mapping, as well as cloning and expression analyses. The comparison of QTL maps of Rubus and Fragaria × ananassa suggests that homologous genomic regions may be important in the expression of various fruit quality traits.