Development of inflorescence primordia in Vitis vinifera L. cv. Chardonnay from hot and cool climates

Background and Aims: The purpose of this study was to gain a quantitative understanding of environmental effects on the formation of yield potential; it is critical that the timing of anlagen initiation and differentiation in latent buds is defined for economically important Vitis vinifera L. cultivars in a range of environments. Methods and Results: This study combined scanning electron microscopy with light microscopy to compare the timing and extent of inflorescence primordia (IP) initiation and differentiation (branching) in primary latent buds of Chardonnay vines grown in a hot (mean January temperature (MJT) 22.3°C) and a cool (MJT 18.1°C) climate. Initiation of anlagen (uncommitted primordia) in dormant buds at node 4 commenced 4 weeks after budburst (BB) in the hot climate and 6 weeks after BB in the cool climate. Subsequent differentiation of anlagen was first observed 6 and 9 weeks after BB in the hot and cool climate, respectively. Conclusions: The extent of IP differentiation varied with climate, with hot climate buds at modified Eichorn and Lorenz scale (E-L) (Coombe 1995) stage 33 being more advanced, larger and exhibiting more widespread secondary branching than cool climate buds. Significance of the Study: This research provides new insights into the timing and extent of reproductive development in Australia's most important white grape cultivar, Chardonnay, thereby having implications for strategic management and forecasting potential yield.