Classification of 98 Different Citrus Species and Cultivars by Fruit Quality and Their Disorders as Related to Delayed Harvest

Fruits of 98 different citrus species and cultivars grown on a hillside orchard of the Experimental Farm of Kinki University at Arita, Wakayama, were left on the trees from November, 1990 to June, 1991, as part of a delayed harvest project. The effects of delayed harvest on the appearance of fruit disorders and changes in sugar and total titratable acid contents were investigated.1. Disorders that occurred among the citrus species and cultivars (except for 'Fukuhara orange' and 'Shunkokan') were classified as : 1) physiolgical, e. g. granulation followed by fruit dropping or pell puffing ; 2) external, e. g. frost injury, abscission and decay ; and 3) complex, e. g. frost injury, granulation and subsequent abscission. The disorders also seemed to occur earlier in the season in early maturing species and cultivars than in later maturing ones.2. The species and cultivars were divided on the basis of sugar accumulation patterns into four groups : group A consisted of species and cultivars which accumulated more than 11% total sugars (TS) before spoiling ; members of group B accumulated a maximum of 10% TS and then it leveled off ; those in group C accumulated a maximum of only 8% before abscising ; and species and cultivars in group D had TS content of less than 5%. 'Miyagawa Wase', Kishu mikan and Ponkan (kosho) in group A accumulated more than 15% TS.3. Fruit disorders were accompanied with a reduction in juice content and a concurrent depletion and/or changes in the relative levels of sucrose, glucose and fructose.We found that the quality of early satsuma mandarin, 'Miyauchi iyokan' and 'Kiyomi' improved significantly and that they did not develop any physiological disorders attributable to delayed havest.