Husk spot caused by the Pseudocercospora macadamiae fungus induces premature abscission of fruit in many industry standard macadamia cultivars. Fungicides and other management strategies add to farm costs, thus breeding for varietal resistance is important. Genetic parameters of husk spot symptom expression had not previously been estimated. To guide selection methods for field resistance, over 300 open-pollinated seedlings of 32 families and 24 parent genotypes were inoculated, and seven symptom expression traits were evaluated. Narrow-sense and broad-sense heritabilities were estimated, breeding values were predicted, and correlations between breeding values of trait pairs were tested for significance. The traits with the highest heritabilities were necrotic lesion number per fruit (H² = 0.41–0.59; h² = 0.21–0.30) and necrotic incidence (H² = 0.19–0.27; h² = 0.17–0.24). Breeding values of the two traits were highly correlated (r = 0.98; p < 0.001), suggesting that either trait could be used to indirectly select for the other. All genotypes expressed symptoms to some degree, however, breeding values for necrotic traits and symptom-induced premature abscission were low for clones and progeny of cultivar ‘HAES791’. Necrotic trait breeding values were also promising for progeny of cultivar ‘HAES246’ and clones of Australian Macadamia Breeding Program elite selection, ‘BAM263’. Having been identified as potentially partially resistant, these selections can now be further evaluated and used as parents of new progeny populations.

由Pseudocercospora macadamiae真菌引起的壳斑会导致许多符合行业标准的澳洲坚果品种果实过早脱落。杀菌剂和其他管理策略增加了农场成本，因此品种抗性育种很重要。以前没有估计壳斑症状表达的遗传参数。为了指导田间抗性的选择方法，接种了 32 个科和 24 个亲本基因型的 300 多株开放授粉的幼苗，并评估了 7 个症状表达性状。估计了狭义和广义遗传力，预测了育种值，并检验了性状对育种值之间的相关性是否显着。遗传力最高的性状为单果坏死病斑数（H²  = 0.41–0.59；h ²  = 0.21–0.30) 和坏死发生率 ( H ²  = 0.19–0.27; h ²  = 0.17–0.24)。这两个性状的育种值高度相关（r = 0.98；p < 0.001)，表明任一特征均可用于间接选择另一个特征。所有基因型都在一定程度上表现出症状，但是，栽培品种“HAES791”的克隆和后代的坏死性状和症状诱导的过早脱落的育种值较低。坏死性状育种价值也有望用于品种“HAES246”的后代和澳大利亚澳洲坚果育种计划精英选择“BAM263”的克隆。已被确定为潜在的部分抗性，这些选择现在可以进一步评估并用作新后代种群的亲本。