Ppm. Iannetta et al., The role of ethylene and cell wall modifying enzymes in raspberry (Rubus idaeus) fruit ripening, PHYSL PLANT, 105(2), 1999, pp. 338-347
This study focuses on four raspberry (Rubus idaeus) genotypes from tno diff
erent genetic backgrounds: cvs Glen Prosen and Glen Clova, bred at the Scot
tish Crop Research Institute (SCRI) and genotypes bred at Horticulture Rese
arch International (HRI), East Mailing (EM), EM 1997 and EM 5007. The ripe
fruit of each genotype pair were characterised subjectively by raspberry br
eeders as relatively firm or soft, respectively. Different stages of fruit
development from each genotype were used to quantify fruit firmness, rates
of ethylene evolution and ripening rate. Penetrometry data confirmed suspec
ted firmness differences, Firmness correlated,vith rates of ethylene evolut
ion. Rates of ethylene production also correlated with receptacle size. Sto
rage of green fruits in 20 mu l 1(-1) ethylene reduced fruit firmness, enha
nced respiration rate and colour (anthocyanin) development and stimulated t
he development of cell wall hydrolase activities. However, during natural r
ipening in the field, fruit respiration rate declined, which indicates a no
n-climacteric ripening pattern. In drupelets, the activities of polygalactu
ronase (PC;). pectin methylesterase (PME)I Cx-cellulase (Cx) and beta-galac
tosidase (beta-gal,) increased substantially as ripening progressed, More d
etailed studies with ripe fruit of cv. Glen Clova indicated major isoforms
of PC at pIs 3.3, 8.6 and 10.1; of PME at pIs 7.2, 8.5, 8.7, 8.8; of Cx at
pi 2.4 and of beta-gal. at pIs 6.3 and 6.7.