Variability of Mangosteen (Garcinia mangostana L.) in Kerala

Abstract

The study entitled ‘Variability of mangosteen (Garcinia mangostana L.) in Kerala’ was conducted under Department of Fruit Science, College of Agriculture, Vellayani during the period of October 2020 to December 2021 with an objective of assessing the variability and identification of elite clones in mangosteen grown in Kerala. Since Wayanad and Thrissur districts represent the major mangosteen growing areas of Kerala, assessment of the variability of the crop was done in different agro ecological units (AEUs) of Wayanad (AEU 15 and AEU 20) and Thrissur districts (AEU 10). A total of 153 trees were selected for the study. Morphological and biochemical characters, abiotic stress (sun burn) susceptibility and incidence of pests, diseases and physiological disorders were recorded from each tree (accession). Variability was observed in qualitative characters like flower and fruit clustering habit, flowering season, fruit size and fruit skin thickness. Dendrogram based on these qualitative characters by UPGMA method grouped 153 accessions into 6 different clusters at a Euclidean similarity distance measure of 1.5. Clusters I, III and IV together consisted of accessions of Wayanad district (AEU 15 and 20) had small and medium sized fruits with medium fruit skin. Cluster I had accessions possessing a combination of flower/fruit clusters which have 1, 2 and 3 flowers/ fruits per cluster. Accessions which flower either during February to April period or April to May period were seen in this cluster. Accessions in cluster III had a combination of flower/fruit clusters posessing either 1 or 2 flowers/fruits per cluster. Flowering was from April to May and May to June. Cluster IV consisted of accessions which had one flower and fruit per flower/fruit cluster. Flowering seasons were same as that of cluster III. Cluster II, V and VI consisted of accessions from Thrissur (AEU 10) only and these accessions had small sized fruits with thin fruit skin. Accessions of cluster II had a combination of flower/fruit cluster with 1 or 2 flowers/fruits per cluster. Flowering season of this cluster was from February to April. Accessions of cluster V had flower/fruit 177 clusters which were similar to that of cluster II. Flowering season of this cluster was from March to April. Cluster VI consisted of two types of accessions; those which produce flower/fruit clusters of single flower/fruit only and those which produce a combination of flower/ fruit clusters of either 1, 2 or 3 flowers/fruits. The flowering season was the same as that of cluster V. Dendrogram based on twenty six quantitative characters, formed using UPGMA method, grouped the accessions into 8 different clusters at a Euclidean similarity distance measure of 30. Principal component analysis (PCA) based on tree and leaf characters revealed that PC1, PC2 and PC3 together contributed 70.95% of variance and had correlation with traits such as age, tree height and leaf petiole width. The loading plot revealed that tree age and tree height; leaf blade length and leaf blade width were the variables having strong positive correlation. PCA bi-plot indicated that Acc.013 to Acc.020, and Acc.077 to Acc 082 were highly diverse from other accessions and the characters contributing to their variance were mainly age of the tree and tree height. PCA based on inflorescence and fruit characters revealed that first six principal components accounted for 67.99% of the total variance among the accessions. Characters contributed mainly to the variance were number of aborted seeds, TSS/acidity ratio, number of mature seeds and acidity. Loading plot showed a strong positive correlation between fruit length and fruit diameter. A strong negative correlation was observed between four pairs of characters. They are number of matured seeds and number of aborted seeds, TSS-acidity ratio and acidity, fruit length and edible portion and fruit diameter and edible portion. PCA bi-plot showed that 30 accessions of Thrissur district i.e., from Acc.124 to Acc.153 were diverse from other accessions and maximum contribution to their variance was from characters like number of aborted seeds or matured seeds and TSS/acidity ratio. The above results indicated that considerable variability exists in qualitative and quantitative characters of mangosteen. Clustering of 62 identified elite clones based on fruit characters like fruit size, edible portion, TSS and acidity using PCA score plot gave 12 different clusters. 9 superior clones (Acc.004, Acc.042, Acc.057, Acc.104, Acc.005, 178 Acc.017, Acc.048, Acc. 121 and Acc.037.) were identified based on economical characters like fruit weight and edible portion. Seven accessions among the identified superior clones were located at RARS Ambalavayal (AEU 20) and two accessions were located at the farmer’s field in Meppadi (AEU 15) of Wayanad district. In future, these nine superior clones could be used for the multiplication of elite clones as well as for creating a germplasm of superior clones. Also, the accessions identified with variations should be subjected for molecular characterization for checking whether variability exists in genetic level. Mangosteen accessions under this study were not susceptible to sun burn. Mild incidence of minor pests and diseases like thrips, mealy bugs, algal spot and anthracnose were observed and were managed at the field itself. Physiological disorders found in mangosteen accessions were gamboge and translucent flesh disorder (TFD).