Changing sink strengths influence translocation of phosphonate in avocado (Persea americana Mill.) trees

Whiley, A. W.; Hargreaves, PA; Pegg, K. G.; Doogan, VJ; Ruddle, LJ; Saranah, J. B.; Langdon, P. W.

doi:10.1071/ar9951079

Cited by 37 publications

(15 citation statements)

References 20 publications

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“…Flowering occurs between early September to mid-October, followed by two fruit drop events usually between late October to January [39]. Harvesting of avocado fruits normally occurs over a split harvest where the larger fruits are removed first, allowing more time for the smaller fruit to grow [40]. In Childers, harvest commences in April depending on fruit maturity, which is determined by ripening and dry matter testing, and continues until late July.…”

Section: Introductionmentioning

confidence: 99%

Using Worldview Satellite Imagery to Map Yield in Avocado (Persea americana): A Case Study in Bundaberg, Australia

2017

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Accurate pre-harvest estimation of avocado (Persea americana cv. Haas) yield offers a range of benefits to industry and growers. Currently there is no commercial yield monitor available for avocado tree crops and the manual count method used for yield forecasting can be highly inaccurate. Remote sensing using satellite imagery offers a potential means to achieve accurate pre-harvest yield forecasting. This study evaluated the accuracies of high resolution WorldView (WV) 2 and 3 satellite imagery and targeted field sampling for the pre-harvest prediction of total fruit weight (kg·tree −1 ) and average fruit size (g) and for mapping the spatial distribution of these yield parameters across the orchard block. WV 2 satellite imagery was acquired over two avocado orchards during 2014, and WV3 imagery was acquired in 2016 and 2017 over these same two orchards plus an additional three orchards. Sample trees representing high, medium and low vigour zones were selected from normalised difference vegetation index (NDVI) derived from the WV images and sampled for total fruit weight (kg·tree −1 ) and average fruit size (g) per tree. For each sample tree, spectral reflectance data was extracted from the eight band multispectral WV imagery and 18 vegetation indices (VIs) derived. Principal component analysis (PCA) and non-linear regression analysis was applied to each of the derived VIs to determine the index with the strongest relationship to the measured total fruit weight and average fruit size. For all trees measured over the three year period (2014, 2016, and 2017) a consistent positive relationship was identified between the VI using near infrared band one and the red edge band (RENDVI1) to both total fruit weight (kg·tree −1 ) (R 2 = 0.45, 0.28, and 0.29 respectively) and average fruit size (g) (R 2 = 0.56, 0.37, and 0.29 respectively) across all orchard blocks. Separate analysis of each orchard block produced higher R 2 values as well as identifying different optimal VIs for each orchard block and year. This suggests orchard location and growing season are influencing the relationship of spectral reflectance to total fruit weight and average fruit size. Classified maps of avocado yield (kg·tree −1 ) and average fruit size per tree (g) were produced using the relationships developed for each orchard block. Using the relationships derived between the measured yield parameters and the optimal VIs, total fruit yield (kg) was calculated for each of the five sampled blocks for the 2016 and 2017 seasons and compared to actual yield at time of harvest and pre-season grower estimates. Prediction accuracies achieved for each block far exceeded those provided by the grower estimates.

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Section: Introductionmentioning

confidence: 99%

Using Worldview Satellite Imagery to Map Yield in Avocado (Persea americana): A Case Study in Bundaberg, Australia

2017

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“…In-planta phosphite concentrations in leaves of injected avocado were maximal and greater than in roots 1 week after injection, but were less in leaves than roots 5 to 10 weeks after application (Whiley et al 1995). The relative distribution of phosphite between plant parts will be a dynamic situation depending on time after application and source-sink relationships affected by environment, growth fluxes of different plant parts and losses through exudation and leaf and root shedding (Whiley et al 1995). Further study of phosphite source-sink relationships in native plant species of Western Australia is needed in order to better understand the persistence of effective in-planta phosphite levels in roots.…”

Section: Discussionmentioning

confidence: 88%

“…However in-planta phosphite concentrations were greatest in leaves, intermediate in stems and least in roots, 2-wk-after low volume spray of B. grandis in a forest environment (Aukland 2002) and similar for roots and stems of glasshouse-grown B. grandis ) and C. calophylla (Fairbanks et al 2000). In-planta phosphite concentrations in leaves of injected avocado were maximal and greater than in roots 1 week after injection, but were less in leaves than roots 5 to 10 weeks after application (Whiley et al 1995). The relative distribution of phosphite between plant parts will be a dynamic situation depending on time after application and source-sink relationships affected by environment, growth fluxes of different plant parts and losses through exudation and leaf and root shedding (Whiley et al 1995).…”

Section: Discussionmentioning

confidence: 98%

Variation within the genus Lambertia in efficacy of low-volume aerial phosphite spray for control of Phytophthora cinnamomi

Shearer¹,

Crane²

2011

Australasian Plant Pathol.

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Soil and stem wound inoculation was used to determine variation in phosphite efficacy for the control of Phytophthora cinnamomi within the genus Lambertia. Disease progress curves following soil inoculation with P. cinnamomi were analysed with the parameters of the logistic model. The asymptote and lag logistic model parameters of disease progress better differentiated between phosphite treatments than the rate parameter. Low-volume phosphite spray significantly reduced the asymptote K max of % mortality and significantly increased the delay t 1/2K for all Lambertia taxa soil inoculated. K max was significantly negatively correlated with delay t 1/2K and taxa sprayed with 48 kg phosphite/ha had a lower K max and longer delay t 1/2K than taxa not sprayed. Phosphite significantly reduced colonisation by P. cinnamomi in stems of 19% of Lambertia taxa tested. The differences in phosphite efficacy between soil and wound inoculation suggests that phosphite may inhibit the infection process more than post-infection stem colonisation. The lack of direct relationships between control of P. cinnamomi and tissue phosphite concentrations may be related to different effective phosphite thresholds between taxa. Time-course studies of in-planta phosphite concentrations in relation to effective control of P. cinnamomi are required in different plant species and environments.

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“…Although injections in spring resulted in a higher percentage of trees improving in health and in fewer dead trees in comparison with the control trees, the benefits were not significant for any category of tree decline. Trunk injection with phosphonates is partic- ularly effective for the control of Phytophthora diseases of tree crops (Diczbalis et al 2004;Guest et al 1995;Opoku et al 2007;Whiley et al 1995). However, the control of P. cinnamomi and the control of oak decline should clearly be differentiated.…”

Section: Discussionmentioning

confidence: 97%

“…Concentrations of phosphonate in roots of Persea americana and Durio sp. varied significantly depending on tree phenology and environmental conditions (Diczbalis et al 2004;Whiley et al 1995). Moreover, the efficacy of potassium phosphonate would depend on the amount applied and taken up in relation to plant size, and the tree species (Hardy et al 2001;Shearer et al 2006).…”

Section: Discussionmentioning

confidence: 98%

Evaluating potassium phosphonate injections for the control of Quercus ilex decline in SW Spain: implications of low soil contamination by Phytophthora cinnamomi and low soil water content on the effectiveness of treatments

et al. 2009

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The Iberian forests are suffering severe disease and mortality as a result of decline, with Quercus ilex the major species at risk. Trunk injections with potassium phosphonate, which have been used successfully to control Phytophthora cinnamomi, were tested against decline. In an area in which P. cinnamomi was isolated, Q. ilex trees showing different degrees of decline were trunkinjected. Soil properties, and measurements of soil water content (θ) and depth to soil water table were assessed at three sites with markedly different decline incidences. Over the 5 years following the initiation of the experiment, mean symptoms among springtreated trees and autumn-treated trees, or among trees injected twice a year (spring and autumn), once a year, and non-injected, were not significantly different. No effects of the treatments on shoot growth and acorn production were observed. However, θ values under trees which recovered from decline were higher than θ values under trees which did not recover from decline. At the site with the highest incidence of decline and tree mortality, P. cinnamomi was rarely isolated, and the presence of gravel, soil infiltration capacities and water table depth values were significantly higher than at the other sites, water stress being more likely to contribute to decline than P. cinnamomi. In areas in which θ is low, the distribution of phosphonate on the tree would be limited. Since the thresholds for phytotoxicity of potassium phosphonate in Q. ilex trees at the site studied would be higher than the amounts used, rates of the chemical slightly less than those that cause phytotoxicity should be tested.

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Changing sink strengths influence translocation of phosphonate in avocado (Persea americana Mill.) trees

Cited by 37 publications

References 20 publications

Using Worldview Satellite Imagery to Map Yield in Avocado (Persea americana): A Case Study in Bundaberg, Australia

Using Worldview Satellite Imagery to Map Yield in Avocado (Persea americana): A Case Study in Bundaberg, Australia

Variation within the genus Lambertia in efficacy of low-volume aerial phosphite spray for control of Phytophthora cinnamomi

Evaluating potassium phosphonate injections for the control of Quercus ilex decline in SW Spain: implications of low soil contamination by Phytophthora cinnamomi and low soil water content on the effectiveness of treatments

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