Phenotypic classification study of 68 macadamia germplasm resources

【Objective】The purpose of the study was to conduct aphenotypic classification study on 68 macadamia germplasm resources with planting value, and to provide a scientific basis for systematic classification and evaluation of macadamia germplasm resources.【Method】The 64 phenotypic traits(39 descriptive traits and 25 numerical traits) of 68macadamia germplasm resources originating from domestic and foreign countries were observed and described according to the identification and evaluation methods in Description Specification and Data Standard for Macadamia Germplasm Resources and Technical Specification of Identification for Macadamia Germplasm Resources, and cluster analysis and principal component analysis were performed based on them.【Result】Based on cluster analysis of flower phenotypic traits, 68 germplasms were divided into 3 groups:type with long inflorescence and multiple flowers, hybrid type with medium length inflorescence and multiple flowers, and type with short inflorescence and few flowers. Based on cluster analysis of leaf phenotypic traits, 68 germplasms were divided into 4 groups:Macadamia integrifolia with big leaf, M. integrifolia with medium leaf, M. integrifolia with small leaf, and M. integrifolia/M. tetraphylla hybrid with big leaf. Based on cluster analysis of fruit phenotypic traits, 68 germplasms were divided into 4 groups:M. integrifolia with big fruit, M. integrifolia with medium size of fruit, M. integrifolia with small fruit, and M. integrifolia/M. tetraphylla hybrid with big fruit. Based on cluster analysis of other phenotypic traits, 68 germplasm were divided into 3 groups:type of high yield and mid-late ripening, type of medium yield and early to medium ripening, and type of low yield and early to medium ripening. Based on comprehensive cluster analysis, 68 germplasm were divided into 4 groups:type with big leaf, big fruit and multiple flowers, type with medium size leaf, small fruit and few flowers, type with small leaf, medium size fruit and few flowers, and hybrid with big leaf, big fruit and multiple flowers. Based on principal component analysis and two-dimension scatter plot analysis of 64 phenotypic traits, 15 main influencing factors that could systematically evaluate classification of 68 germplasm phenotypic traits were selected. The 15 main influencing factors included fresh weight of single fruit with pericarp, fresh weight/dry weight of single shellfruit, leaf shape/leaf shape index, fruiting ability, flowering ability, flower quantity, flower color, maturity characteristics, leaf edge thorn density, surface texture of shellfruit, young leaf color, weight of single kernel, leaf area, leaf petiole length, and leaf inflorescence.【Conclusion】The clustering analysis based on phenotypic traits such as flowers, leaves, and fruits supports the existing classification system of macadamia. The representative main influencing factors can scientifically and systematically evaluate the phenotypic classification of macadamia germplasm resources.