ACTINIDIN LEVELS IN FRUIT OF ACTINIDIA SPECIES AND SOME ACTINIDIA-ARGUTA ROOTSTOCK SCION COMBINATIONS

Actinidin, the kiwifruit protease, was measured in the fruit of a numb er of Actinidia species during their growth, at harvest and during sub sequent storage Actinidia deliciosa cv. Hayward (kiwifruit) fruit acti nidin levels were compared to fruit levels measured in cutting-grown p lants of species to be used as rootstocks, A. arguta selections and so me rootstock-scion combinations. The fruit showed a wide range of acti nidin activities, which were influenced by the scion and rootstock gen otype. Some trends were seen in rootstock-scion combinations; rootstoc ks whose fruit had low actinidin levels conferred low levels in the fr uit of grafted scion species. Similarly high levels were seen in scion fruit whose rootstock had high levels. There was a significant scion influence in some combinations. The correlation between actinidin and protein levels suggested control at transcription. An SDS-PAGE gel sho wed that the density of the actinidin band correlated with the measure d actinidin levels. The data suggested that variation in actinidin act ivity was not due to endogenous inhibitor control or the presence of a n inactive zymogen.