Alpha-amylase activities and activity gel profiles were measured in ki
wifruit Actinidia deliciosa var. deliciosa ([A. Chev.], C. F. Liang an
d Ferguson cv. Hayward) during fruit development and postharvest ripen
ing. As fruit developed, alpha-amylase activity increased on a per fru
it basis, mirroring the increase in starch content in the fruit. Alpha
-amylase activity increased approximately 2-fold between 134 days afte
r anthesis (DAA), (when fruit starch content is at its maximum before
beginning to decline) and harvest. During postharvest ripening with an
d without ethylene treatment at 20 degrees C, or during postharvest st
orage at 0 degrees C, enzyme activity remained similar to harvest valu
es until fruit were ripe and most of the starch converted to sugars. A
t this point activity decreased 4-5-fold. Several amylolytic bands as
well as starch phosphorylase and debranching enzyme were visible in st
arch activity gels. Starch phosphorylase was lower in ripe fruit, as w
as the intensity of two amylolytic bands. None of the other amylolytic
bands or the debranching enzyme changed in response to fruit developm
ent or ripening. The same results occurred if gels were incubated at p
H 6.1 or pH 8.0. These results are discussed in relation to the initia
tion of net starch degradation at the commencement of fruit ripening.