Phenotypic Evaluation of Introduced Melaleuca alternifolia Resources in Northern Guangdong Province

In order to disclose the potential productivity of terpinen-4-olchemotype of Melaleuca alternifolia in northern Guangdong Province, a total of 211 individuals were selected from the 4-year-old stand of mixed progenies introduced from Australia, and subjected to an analysis on 9 economic traits concerning with biomass, essential oil productivity and quality-effecting ingredients. The correlation analysis, principal component analysis and weight estimation of traits were used to detect growth traits and chemical components, and screen out superior individuals. The findings indicated that 3 biomass traits, height (HT), diameter at breast height (DBH) and crown sectional area (CSA), had coefficients of variations (CVs) varying from 15.38% to 44.74%. The active-ingredient productivity traits, fresh-leaf terpinen-4-olchemotype concentration, had a CV of 20.66% suggesting a considerable potential in genetic improvement. The analysis on essential oil ingredients revealed that 94.58% of testing individuals were terpinen-4-olchemotype chemotype. The percentage of terpinen-4-olchemotype in essential oil only significantly had positive association with HT. Fresh-leaf terpinen-4-olchemotype concentration was positively and significantly related to both fresh-leaf oil concentration and percentage of terpinen-4-olchemotype, whereas it showed various degrees of negative relatedness to growth traits and other chemical ingredients in essential oil. The selection based on composite selection indices (I_C) and 15% of selection ratio screened out a total of 12 superior individuals with outstanding performance in growth, fresh-leaf oil concentration, percentage of terpinen-4-olchemotype and essential oil quality. These superior individuals had realistic gains ranging from 6.61% to 47.63% in terms of 5 key economic traits.