Fruiting character variability in wild individuals of Malania oleifera, a highly valued endemic species

Abstract

Malania oleifera (Olacaceae), a tree species endemic to Southwest China, has seed oils enriched with nervonic acid and is therefore good source of this chemical. Because of this, there are promising industrial perspective in the artificial cultivation and use of this species. Understanding the variability in the fruit characters among individuals forms the basis or resource prospection. In the current investigation, fifty-three mature fruiting trees were sampled from two locations with divergent climates (Guangnan and Funing). Morphological characterization of fruits (fruit and stone weight, fruit transverse and longitudinal diameter, stone transverse and longitudinal diameter) was conducted, and the concentration of seed oil and its fatty acid composition were also analyzed in all individuals. Differences in all the morphological characters studied were more significant among individual trees than between different geographic localities, even though these had different climates. Eleven fatty acids were identified contributing between 91.39 and 96.34% of the lipids, and the major components were nervonic acid (38.93-47.24%), octadecenoic acid (26.79-32.08%), docosenoic acid (10.94-17.24%). The seed oil content (proportion of oil in seed kernel) and the proportion of nervonic acid were both higher in Funing, which has a higher average climatic temperature than Guangnan. The concentrations of nervonic acid and octadecenoic acid with the low coefficients of variation in the seed oil of M. oleifera were relatively stable in contrast to the other fatty acids. There were significant positive correlations between fruit morphological characters, but the amount of seed oil and the concentrations of its components were not correlated with any morphological character. This study provides an understanding of morphological variation in wild M. oleifera individuals. Wild individuals with excellent fruit traits could be selected and would make promising candidates for commercial cultivation.

Figure 1

Fruit morphology of Malania oleifera. (A) Structure of fruit. (B) Stone size comparison of samples from Guangnan. (C) Stone size comparison of samples from Funing. (a) and (d): individuals with the largest average STD. (b) and (e): individuals with the medium average STD. (c) and (f): individuals with the smallest average STD. FTD fruit transverse diameter, FLD fruit longitudinal diameter, STD stone transverse diameter, SLD stone longitudinal diameter.

Figure 2

Correlations between fruit traits of individuals in Guangnan and Funing. FW fruit weight, SW stone weight, FTD mean fruit transverse diameter, FLD mean fruit longitudinal diameter, STD mean stone transverse diameter, SLD mean stone longitudinal diameter, OPT the outer pericarp thickness, SOC seed oil content. *p < 0.05; **p < 0.01.

Figure 3

Correlations between fatty acid components in the seed oil from individuals in Guangnan and Funing. HEA hexadecenoic acid, HAA hexadecanoic acid, ODA octadecadienoic acid, OEA octadecenoic acid, OAA octadecanoic acid, DEA dodecenoic acid, ACC arachidic acid, DSA docosenoic acid, DAA docosanoic acid, NVA nervonic acid, TAA tetracosanoic acid. *p < 0.05; **p < 0.01.