RAPID MESOCARP CELL ELONGATION ENHANCES GUMMING SYNDROME IN JAPANESE APRICOT (PRUNUS MUME SIEB. ET ZUCC.) FRUIT

Abstract

Japanese apricot (Prunus mume Sieb. et Zucc.) 'Benisashi' fruit tends to show the physiological disorder of a gumming syndrome, while the fruit known as 'Nanko' rarely show this. The accumulated gum becomes a solid gel during the processing period and the commercial value of the mume pickle is consequently decreased. In the present experiment, gum accumulation in the mesocarp tissue and the cell size of the tissue during fruit growth were observed in the two cultivars. In mid-May, the initiation of the gum duct was observed in vascular bundles in the mesocarp tissue of the two cultivars and plant gum was then observed to accumulate in the duct. No difference in these phenomena was observed between the cultivars until late May. Thereafter, 'Benisashi' developed a gum lump visible to the naked eye during Stage III, while the gum lump of 'Nanko' did not develop to the visible size as shown in 'Benisashi'; the lumps could not be confirmed with the naked eye until the mature stage. 'Benisashi' showed more rapid fruit growth compared with 'Nanko' during Stage III due to explosive mesocarp cell elongation close to the endocarp. Moreover, the rate of gumming fruit of 'Benisashi' was higher in bigger fruits than smaller ones. These results indicate that the peculiar cell growth of 'Benisashi' fruit may accelerate gum lump formation.3 Corresponding

Gum Accumulation of Japanese Apricot Fruit (Prunus mume Sieb. et Zucc.) was Expedited by Jasmonate

“…In a previous study, we reported that 'Benisashi' fruit grew more rapidly than 'Nanko' fruit during the rapid mesocarp development stage, just before the fruit ripened (stage III), due to explosive mesocarp cell elongation close to the endocarp. The uncoordinated cell growth between the inner and outer mesocarp of 'Benisashi' fruit may cause cracks at junction areas of inner and outer mesocarp cells, leading to the accumulation of gum in the cracks; however, this phenomenon does not occur in 'Nanko' fruit (Matsumoto et al, 2008). The rapid mesocarp development stage usually starts in the first ten days of May.…”

“…On the other hand, 'Nanko' fruit does not develop gumming syndrome until fruit maturation (Yamaguchi et al, 2004). A previous report (Matsumoto et al, 2008) indicated that, in mid-May, gum duct initiation and plant gum accumulation could be observed in vascular bundles in the mesocarp tissue of both 'Benisashi' and 'Nanko' Japanese apricot fruit; however, although 'Nanko' fruit does not develop a gum lump that is visible to the naked eye until the mature stage, 'Benisashi' fruit develops clearly visible gum lumps. Morrison and Polito (1985) reported that a gum duct forms naturally in many kinds of cultivated Prunus species; however, gum production is intensified after mechanical or insect damage, pathogenic infection, or 274 exposure to ethylene-producing chemicals (Bukovac, 1979;Martin and Nelson, 1969;Morrison et al, 1987;Olien and Bukovac, 1982;Saniewski et al, 2006).…”

“…Hence, before this stage, ibuprofen treatment can effectively reduce JA-Me-induced gum formation (Table 3). Furthermore, uncoordinated cell growth between the inner and outer mesocarp generally starts by the end of May (Matsumoto et al, 2008), although by this time the endogenous jasmonate content might have already increased. Thus, ibuprofen treatment did not suppress gum formation of either wounded (Table 2) or intact (Table 3) Japanese apricot fruit.…”

“…Thus, Saniewski et al (2006) suggested that gum formation might be co-regulated by the ratio of the relative concentration of ethylene and jasmonates. Gum formation of Japanese apricot fruit is reportedly induced by explosive mesocarp cell elongation close to the endocarp during the rapid mesocarp development stage just before fruit ripening (Matsumoto et al, 2008;Yamaguchi et al, 2004); however, the influence of plant hormones on the gum formation of Japanese apricot fruit has not been studied.…”

“…Despite these intrinsic features, 'Benisashi' is prone to develop a physiological disorder of fruit flesh known as gumming syndrome. This syndrome affects the quality of the mume pickle because the accumulated gum becomes a solid gel during the processing period, and the commercial value of the mume pickle is consequently decreased (Matsumoto et al, 2008). Tamura et al (2002) reported that among mume cultivars classified as mume-type (Yoshida and Yamanishi, 1988), the 'Benisashi' fruit has a high incidence of gumming syndrome during the exponential stage of fruit growth.…”