Seasonal and regional variation in budbreak and flowering of kiwifruit vines in New Zealand

Abstract

Measurements of the timing and amount of budbreak and flowering in 'Hayward' kiwifruit were made over 4 years in six regions of New Zealand. There was a large variation in the vine attributes measured. The number of flowers produced/winter bud varied 5-fold between the worst site-year combination and the best. The time of 50% budbreak varied by 32 days and the time of 50% flowering by 25 days. The proportion of flowers on the distal (tip) two buds ranged in a single year from a low of 10% at one site to > 65% at another on canes which had an average of 21 buds. The number of flowers/winter bud is considered to be made up of four components: the proportion of budbreak, the proportion of floral buds, the number of inflorescences/floral bud, and the number of flowers/ inflorescence. The proportion of budbreak and the proportion of floral buds were found to be most important in determining the number of flowers produced/winter bud, and both of these components were significantly higher at the cooler, southern, sites. The vines measured in this survey were all H93053 chosen from a single block in a single orchard within each region, so between-vine variation was minimised. Despite this, total between-vine variation accounted for nearly 40% of the observed variance in the proportion of budbreak and about a quarter of the observed variance in the number of flowers/ winter bud and the proportion of floral buds. Differences between regions were significant for all vine attributes measured except the number of inflorescences/floral bud, with cooler sites generally breaking bud earlier and producing more flowers. When averaged over all 4 years, the number of flowers/winter bud was over twice as high at the coolest site than at the warmest, and budbreak occurred more than 3 weeks earlier. The proportion of flowers on the tip two buds varied from an average of < 17% at one site to > 50% at the warmest site. Year-to-year differences were generally not significant when averaged over all regions, except that flowering tended to be early or late at all sites in the same years. Year-to-year variation was however very important within each region. Over 50% of the variance in the number of inflorescences/ floral bud was the result of year-to-year variation, and over a third of the variance of the number of flowers/winter bud. At the warmest site, both the number of flowers/winter bud and the proportion of flowers borne by the tip two buds varied more than 2-fold in consecutive years. It is this betweenseason variation that is of major significance in orchard management. It is also important for the industry at large because of the need to organise transport, storage, and marketing on a region-byregion basis.

Climate and kiwifruit cv. Hayward 1. Influences on development and growth

“…These results are consistent with the controlled environment experiments in container grown vines (Warrington & Stanley 1986;McPherson et al 1988). The regression model derived from field data to predict the development rate from end of dormancy to budburst (Equation 5) gave delays in budbreak of 17 days for a reduction in temperature from 12 to 8°C and 16 days for a reduction in temperature from 19 to 10°C.…”

“…Our model gives phase durations of 47 and 81 days at the same temperatures. McPherson et al ( 1988) found a phase duration difference of 97 days between mean temperatures of 19 and 10°C, with our model giving 96 days. The controlled environment experiments show an increase of 8-10 days/°C reduction of temperature.…”

“…The indication from the data that there is a noteably delayed response of budburst to higher winter temperatures is consistent with previous research. Observations of McPherson et al (1988) in controlled environment experiments showed that cooler winter temperatures advance the time of budbreak.…”

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

“…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). Although the LD treatments resulted in a substantial reduction in flowering, the amount of budbreak was not affected and so the LD treatments do not appear to effect the accumulation of winter chilling in kiwifruit.…”

Variation in flowering withinActinidia chinensisvines

“…Chev.) C. F. Liang et A. R. Ferguson 'Hayward' kiwifruit, the timing and amount of flowering have been used to assess the effects of temperature (McPherson et al 1994), growth regulators (Henzell et al 1991), shading (Snelgar et al 1992), thinning (Burge et al 1987), defoliation (Buwalda & Smith 1990), and cane tipping (Manson et al 1991) on vines. However, there have been no studies of how flowering varies within a kiwifruit vine.…”