Environment – genotype interactions and the physiological processes determining fruitfulness and yield in grapevines

Yield instability is estimated to cost the Australian Wine Industry more than $200 million annually. Thus the prediction of yield potential and the management of yield are of utmost importance. This project aimed to explore how the environment and genotypes interact to determine fruitfulness and yield by investigating the stages of grapevine reproduction. Yield potential depends on the transition of apices to a floral state and their subsequent differentiation to an immature stage in developing grapevine buds. The early stages of reproduction are described as initiation and differentiation; they set the maximum fruitfulness and optimal yield potential and are the least understood in grapevine reproduction. For grapevine, inflorescence primordia initiation and partial development occurs in the latent bud in season 1 and largely determines yield potential as defined by inflorescence number per cane and inflorescence branch number. In season 2 the bud bursts and the inflorescence completes development and during this stage inflorescence branching and growth is completed and flower number determined. Final flower number per inflorescence contributes to yield potential but has a smaller effect compared to inflorescence primordia number. The research described in this report focused on genotypic-environmental interactions during the early stages of grapevine reproduction.