Karakterisasi dan evaluasi aksesi pamelo {citrus maxima (burm.) Merr.} berbiji dan tidak berbiji asli Indonesia

Abstract

Indonesia has many accessions of pummelo germplasms, but only a small number of the accessions are planted commercially. Genetic variation in the seed number per fruit in pummelo is high, ranging from seedless to very seedy. Thus pummelo is categorized as seeded, potentially seedless and seedless. The objectives of this research were: 1) to identify morphological, biochemical (isozyme) and molecular (ISSR) characters, and ploidy level of seeded and seedless pummelo accessions originated from Sumedang, Pati, Kudus and Magetan, 2) to identify fruit formation of seeded and seedless pummelo, 3) to evaluate fruit quality of seeded and seedless pummelo fruit quality during storage. The characterization research showed that morphological characters contributed in grouping pummelo accessions were epicarp thickness, leaf lamina margin, vesicle length, epicarp color, petiole wing width and fruit shape, while based on isozyme characters were MDH (Rf 0.11 and 0.14) and ACP (Rf 0.24 and 0.33). ACP band at Rf 0.24 could be used as marker to differentiate seeded and seedless pummelo accessions. Molecular characters supported in classification of pummelo accessions were PKBT8 500 bp, PKBT8 375 bp, PKBT7 750 bp, PKBT3 750 bp, PKBT8 625 bp and PKBT12 500 bp. Separation between seeded and seedless cultivars based on morphological characters occured at similarity coefficient of 0.63, while on isoenzyme characters occured at similarity coefficient of 0.49. Both seeded and seedless pummelo accessions were diploid (2n = 2x = 18). Observation on fruit formation between selected seeded and seedless pummelo demonstrated that those pummelo accessions were able to produce parthenocarpic fruits, but bored seeded fruits when self pollination was induced, thus indicated self-compatibility. Natural self-pollination on ‘Bali Merah 1’, ‘Bali Merah 2, ‘Nambangan’ and ‘Bageng’ yielded seedless fruits, but most of ‘Jawa 3’ was seeded. Artificial self-pollination on those accessions produced seeded fruits, thus showed ovule fertility. ‘Bali Merah 2’ was shown to have high parthenocarpic degree as indicated by less seed number (<10 seed per fruit) in all pollination treatments. Therefore seedlessness in those pummelo accessions was caused by parthenocarpy, was not by pollen and ovule sterility, selfincompatibility, or poliploidy. Evaluation of pummelo fruit quality showed seedless pummelos have higher vitamin C, naringin content and acidity than seeded accessions. Vitamin C and titratable acidity (TA) content decreased, but total soluble solids (TSS) and TSS/AT ratio increased during storage period. During storage, percentage of edible portion increased, mainly due to the decrease of peel weight. Percentage of fruit axis of seedless accessions was smaller than those of seeded accessions. Sensory analysis indicated ‘Jawa 1’ seedless accessions have superior quality based on hedonic and scale quality test.