Flowering development of pome fruit trees is dependent on local environmental conditions. The main driver in the timing of pome fruit flowering is temperature. However, understanding of the effect of temperature at an individual bud scale, is limited. The main purpose of this research was to investigate the differences in green tip timing, one of the earliest stages of flowering development, between bud types and potential temperature drivers. Changes in climate conditions may influence flowering timing potentially leading to a rise in the variability of fruit maturation, increasing harvesting costs as more picks are required. In addition, greater variability can potentially affect cross-pollination as varieties that pollinate each other may have different flowering at different times, limiting pollination potential. Furthermore, a better understanding of the relationships between temperature and individual bud behaviour will assist in assessments of future impacts of climate change on timing of flowering.
Data from three different types of buds from 'Cripps Pink' apple were collected for 2012 and 2013. The study sites, which represent different climatic conditions, were Applethorpe (QLD), Shepparton (VIC) and Manjimup (WA). Statistical tests were applied to the data sets to evaluate possible differences in green tip emergence between bud types, sites and years. The results showed that on average spur buds were the first to burst at all sites. These were closely followed by terminal buds and then axially buds. Comparing across locations buds in Shepparton and Applethorpe were first to burst in both years, and some days later those located in Manjimup. There were significant differences in the day-of-year when individual buds reached green tip between bud types, within and across sites. The length of the green tip phase also varied between buds, sites and years.
There was a consistent relationship between date of green tip and winter temperature. Cooler sites, Shepparton and Applethorpe, had the earliest dates of green tip while Manjimup experienced warmer winter seasons and the latest dates of green tip. Likewise, the warmer winter season, 2013, experienced a delay in the day-of-year when buds reached the green tip phase in all locations compared with 2012. Similarly, the length of the green tip phases was longer for 2013 than 2012.
The results from this study help to further elucidate the relationships between winter temperatures and green tip in 'Cripps Pink' apple. Understanding these relationships is essential for the identification of potential impacts that future climate change may have on apple production in Australia
