Effects of hydrogen cyanamide on budbreak and flowering in kiwifruit (Actinidia deliciosa’Hayward')

Abstract

Effects of hydrogen cyanamide (HC) application to kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A. R. Ferguson 'Hayward') vines were assessed over four seasons in three New Zealand kiwifruit-growing areas. HC advanced the date of budbreak to c. 40 days after application, despite the date of application varying from 33 to 92 days before natural budbreak. For every day that HC advanced budbreak, there was a 0.5-day advance in the date of flowering (r 2 = 0.92). The smaller advance in flowering resulted from the cooler temperatures experienced between budbreak and flowering in the treated vines. HC applications tended to reduce the spread of budbreak and flowering, with the greatest effect at the warmest sites. H01011 Received 19 March 2001; accepted 20 August 2001Application of HC usually increased budbreak and the total number of flowers at the warmest two sites, but only slightly reduced their seasonal variation as this was largely the result of the amount of winter chilling vines received. The number of flowers per winter bud produced by untreated vines was reduced by 0.44 per 1°C. The percentage of total flowers that were lateral or side flowers was reduced by HC application from 14 to 4% at the warmest site and 29 to 19% at the coolest site.

Flowering of kiwifruit (Actinidia deliciosa) is reduced by long photoperiods

“…this is similar to the 40-day average reported by McPherson et al (2001). The LD treatment did not affect the percentage budbreak, but it did significantly reduce both the percentage of shoots that produced flowers (% floral shoots), and the number of flowers on each floral shoot (Table 2).…”

“…Although the period when kiwifruit accumulate winter chilling is not well defined, McPherson et al (2001) found that flower production is negatively correlated with average temperatures during May, June, and July. In the current work, the leaves remained on the vine for over half of this "winter" period and LD treatments were applied until well after leaf fall.…”

“…In the current work, the leaves remained on the vine for over half of this "winter" period and LD treatments were applied until well after leaf fall. Although applying hydrogen cyanamide to kiwifruit vines increases budbreak and flowering, it does not fully compensate for insufficient winter chilling, so flower production still decreases as mean winter temperatures increase (McPherson et al 2001). Consequently, we would expect to see a reduction in both budbreak and flowering if the LD treatments delayed the onset of the accumulation of winter chilling (McPherson et al 1994).…”

“…It is clear that kiwifruit require a period of low temperatures during winter dormancy to achieve adequate flowering in the following spring (McPherson et al 2001). In warm climates, where winter chilling is poor, vine yields are limited by low flower numbers (Allan et al 1999).…”

Identification and sequence characterisation of molecular markers polymorphic between male kiwifruit (Actinidia chinensis var. deliciosa (A. Chev.) A. Chev.) accessions exhibiting different flowering time

“…Hydrogen cyanamide is a molecule used commercially to promote the advance of flowering in kiwifruit, which depends on the temperatures from budbreak to flowering (McPherson et al 2001). In addition, hydrogen cyanamide is able to increase the magnitude of budbreak and flowering, since it promotes flower production by reducing abortion of basal flower buds (Walton and Fowke 1993).…”