Vol. 72 No: 2

Title:
Evaluating Winter Chilling of Kiwifruit Using Excised Canes

Authors:
W.P. SNELGAR, P.J. MANSON and H.G. MCPHERSON

pp: 305-316

Abstract:
Kiwifruit require a certain amount of winter chilling to flower adequately and produce a commercially acceptable yield, but precise temperature requirements have not been defined. Development of a reliable chilling model has been hindered by the difficulty of obtaining data sets which relate bud break and flowering to temperature at specific times during winter. Preliminary work suggested that whole detached canes (15–20 buds) may be effective as experimental units. We used this technique to investigate the temperature responses of kiwifruit during winter. Canes collected from cool, moderate, and warm regions of New Zealand were exposed to cool, ambient, or warm conditions for 27 d periods. The date of bud break was usually advanced by low temperatures during May, June and July and the proportion of bud break was increased. The exception, in both cases, was canes from Riwaka, which became unresponsive to temperature by July. This is consistent with chilling being more advanced in the canes from this coolest site. Flowering was most affected by low temperatures during late winter. The number of inflorescences per winter bud was not affected by May temperatures but low temperatures during June and July increased flowering. Comparison of the temperature responses of canes from the three regions suggests that autumn temperatures have an important effect on vine development during the following spring. Thus the effects of autumn temperatures need to be included in "winter chilling" models. These data will be used together with the responses of entire vines to facilitate the development of chilling models.

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