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Facelli E.,University of Adelaide | Taylor C.,Australian Department of Primary Industries and Fisheries | Williams N.M.,University of Adelaide | Williams N.M.,Murdoch University | And 5 more authors.
Australasian Plant Pathology | Year: 2014

Xanthomonas translucens has been identified as the causal agent of pistachio dieback in Australia. Symptoms include decline, xylem staining, trunk and limb lesions, and excessive exudation of resin. Bacteria were previously isolated from stained wood in 2-year-old twigs but little was known about their presence in other parts of the tree. The pattern of staining and location of X. translucens were studied following felling and dissection of asymptomatic and diseased trees. Chestnut-coloured smears and specks occurred in the sapwood of diseased trees and were continuous from the trunk to 1-2-year-old twigs. X. translucens was isolated mainly from young sapwood (stained and unstained) of the main trunk, primary and younger branches and current season growth, less frequently from leaves and bunches, rarely from old, stained heartwood and not from roots and associated soil samples. Bacteria and pathogenic fungi were not found in the inner bark and cortex associated with lesions whereas the stained sapwood underlying the lesions yielded X. translucens. Scanning electron microscopy revealed bacteria in the main vessels of the xylem of stained tissue and tyloses in the proximity of colonised tissue. Information on the pattern of staining and location of the bacteria will facilitate pathogen detection, thereby improving the accuracy of disease diagnosis. © Australasian Plant Pathology Society 2009.

Zhang J.,Pistachio Growers Association Incorporated | Ranford T.,Pistachio Growers Association Incorporated
Scientia Horticulturae | Year: 2015

To determine the heat accumulation required for bloom and harvest of 'Sirora' pistachio (Pistacia vera) trees, 6510 and 25,609 combinations of base temperature (Tb), optimum temperature (Tu) and critical temperature (Tc) were tested. Using eight seasons' data, we attempted to find the smallest variation for heat accumulation for bloom and harvest. The combination of Tb=-1, Tu=26 and Tc=26 for bloom and Tb=14 and Tc=32 for harvest resulted in the lowest value for the coefficient of variation. Validation was performed using actual harvest data from 2 further years from the orchard used for the initial modelling and 10 years from other orchards in different regions. Reasonable results were obtained for the major Australian pistachio production areas. The data from the cooler Nhill area did not fit this model. The reason for this has been explored. © 2015 Elsevier B.V.

Zhang J.,Pistachio Growers Association Incorporated | Taylor C.,Australian Department of Primary Industries and Fisheries
HortScience | Year: 2011

Determining the chilling requirement for 'Sirora' pistachio (Pistacia vera L.) production in Australia and monitoring winter chill accumulation is desirable to allow growers to take timely mitigating action in years of insufficient chill. Based on greenhouse work, historical data analysis, and field validation, the Chilling Hour, Utah, and Dynamic Models were compared. The Dynamic Model produced the best determination for fulfillment of chilling requirement with 59 chill portions. The required number of growing degree-hours above 4.4 °C from chill fulfillment to 50% bloom was 9633. Relations among the level of fulfillment of chilling requirement, bloom delay, and yield are discussed.

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