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Pericarps retained in the tree canopy and stomatal abundance are components of resistance to husk spot caused by Pseudocercospora macadamiae in macadamia

Akinsanmi, O. A. and Topp, B. and Drenth, A. (2012) Pericarps retained in the tree canopy and stomatal abundance are components of resistance to husk spot caused by Pseudocercospora macadamiae in macadamia. Euphytica, 185 (2). pp. 313-323. ISSN 0014-2336

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Article Link(s): http://dx.doi.org/10.1007/s10681-012-0645-9

Abstract

Pseudocercospora macadamiae Beilharz, Mayers and Pascoe infects macadamia fruit via stomata causing husk spot disease. Information on the variability of fruit stomatal abundance, its association with diseased fruit pericarps (sticktights) that are retained in the tree canopy, and its influence on the husk spot intensity (incidence, severity and lesion number) among macadamia genotypes is lacking. We examined a total of 230 macadamia trees comprising 19 cultivars, 56 wild germplasm accessions and 40 breeding progeny, for the prevalence of sticktights and husk spot intensity over three production seasons. We observed a strong association between the prevalence of sticktights and disease intensity indicating its usefulness as a predictor of husk spot and as a useful phenotypic trait for husk spot resistance selection in breeding programmes. Similarly, stomatal abundance varied among macadamia genotypes, and a significant linear relationship (P < 0.001; 93%) was observed between fruit stomatal abundance and husk spot for all the macadamia genotypes analysed, confirming the utility of that trait for disease resistance screening. The genotypes were grouped into disease resistance groups. Correlations between fruit stomatal abundance, disease intensity and prevalence of sticktights revealed that the numbers of sticktights, and relative stomatal abundance were the main factors influencing the intensity of husk spot among macadamia genotypes. This is the first comprehensive study of natural variation of stomatal abundance in Macadamia species that reveals genetic variation, and provides relevant relationships with disease intensity and the prevalence of sticktights. The phenotypic plant traits indentified in this study may serve as selection tools for disease resistance screening in macadamia breeding programmes.

Item Type:Article
Business groups:Horticulture and Forestry Science
Additional Information:Akinsanmi, Olufemi A. Topp, Bruce Drenth, Andre Australian Government This project is facilitated by Horticulture Australia Limited. The Australian Macadamia Society, CSIRO, DEEDI and QAAFI are all acknowledged for their contributions. The Australian Government provides matched funding for all HAL's R&D activities. Springer Dordrecht
Keywords:Disease resistance Macadamia spp Phenotypic traits Pseudocercospora macadamiae Stomatal abundance Tree nut fruit infection cultivation abscission disease
Subjects:Plant culture > Fruit and fruit culture > Nuts
Plant pests and diseases
Deposited On:18 Mar 2014 03:20
Last Modified:18 Mar 2014 05:05

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