MOLECULAR AND PHYSIOCHEMICAL STUDIES OF FIFTEEN ORANGE (CITRUS SINENSIS L.) CULTIVARS

Abstract

Molecular fingerprints, phylogenetic relationships and physicochemical
characteristics of 15 orange (Citrus sinensis L.) cultivars were studied. The inter
simple sequence repeats (ISSR) technique with seven primers was used. The
dendrogram constructed based on 66 amplification products generated by the ISSR
classified the cultivars into two major clusters. The first cluster included the Blood
orange cultivar only, whereas the second comprised the rest of the cultivars with
different degrees of genetic similarities. The highest phylogenetic relationship was
noted between the two citrus accessions, Mouzambique and Roja, with 96%
similarity. On the other hand, a genetic similarity of 53% was noted between the
Balady orange and the Blood orange. Based on these findings, it could be concluded
that the seven ISSR primers were effective to differentiate the orange cultivars under
investigation. The physicochemical parameters of fruit juice included vitamin C
concentration, pH, percentages of total soluble solids, and titratable acidity. The
Hamlin, Centrial and Roja orange cultivars had the highest concentration of vitamin
C (60.67, 58.33 and 57.14 mg/100 ml-1, respectively). On the contrary, Tanneriffe
cultivar showed the lowest vitamin C concentration (26.55 mg/100 ml-1). The Tunisi
cultivar had the highest pH of 6.443 in contrast to Mafred, Roja and Valencia
accessions with pH vales of 3.317, 3.32 and 3.29. Tunisi and Balady orange cultivars
exhibited the highest percentage of total soluble solids (T.S.S) of 12.3 and 12.07%,
respectively. Whereas Valencia and Mafred showed the least T.S.S expressed by
8.83 and 8.27%, respectively. Roja cultivar recorded the highest (1.397%) titratable
acidity. In contrast, the Succari, Tunisi and Khalili red accessions demonstrated the
least titratable acidity of 0.05, 0.09 and 0.093 %, respectively.