Genetic diversity assessment among Darjeeling mandarin accessions through fruit quality traits grown in Eastern Himalaya regions of India

This study aims to assess the genetic diversity among mandarin accessions grown in the Darjeeling and Kalimpong regions through the analysis of key fruit quality traits. A comprehensive evaluation of 17 orchards over two seasons (2020-21 and 2020-22) measured 18 traits, including fruit weight, volume, pulp weight and total phenol content. The results revealed considerable variation in the studied traits, with high coefficients of variation observed for total phenol content (68.2 %) and number of seeds (33.4 %). Significant correlations were identified among fruit traits, highlighting genetic factors as primary drivers of diversity, with minimal environmental influence. Principal Component Analysis (PCA) and cluster analysis further classified the germplasm into six distinct clusters, emphasizing the genetic distinctiveness of accessions such as DL and KR. Correlation results depicts that fruit traits such as fruit weight is not associated with biochemical traits such as Total Soluble Solids (TSS), Total Phenol Content (TPC), Total Flavonoid Content (TFC) and antioxidants through 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) and by Ferric Reducing Antioxidant Power (FRAP) assay. In other words, bigger fruit size does not necessarily have high biochemical traits. Also, huge variability exists within the mandarin accessions. These high variability, diversity and structure could be utilized for citrus breeding programme, which may be helpful in breeding varieties with high yield and nutritional properties. Thus, genetic variability provides a valuable resource for breeding programs aimed at improving fruit quality and supporting agricultural sustainability in the region.