The effect of pre-budbreak cane girdling on the physical and phenological development of the inner and outer arm in <i>Vitis vinifera</i> L. 'Sauvignon blanc' inflorescence structures
Keywords:bunch architecture, inflorescence, inner and outer arm, grapevine phenology, 'Sauvignon blanc'
The development of inflorescence primordia (IP) into floral bearing structures is influenced by many environmental and genetic factors. We hypothesise that carbohydrate (CHO) availability at budbreak (BB) has a strong influence on IP development, especially during the initial stages of shoot growth when pre-formed IP emerge from dormant buds and may be dependent on reserve CHOs for further branching and development. Carbohydrate availability to developing grapevine buds (Vitis vinifera L. 'Sauvignon blanc') was manipulated by girdling canes two weeks before BB. Dates of flowering, flower number, berry number and grape berry soluble solids (SS) were measured for the inner and outer arm bunch components of basal and apical bunches separately. Restricting pre-BB CHOs resulted in the abortion of some pre-formed inflorescences and reduced branching of the inflorescences that did develop. In general, berry SS were greatest for the basal inner arm, followed by those of the apical bunch inner arm, then those of the basal bunch outer arm, then lastly by those of the apical bunch outer arm. However, this was influenced by the relative berry numbers between the inner and outer arm. Bunches with more similar berry numbers on the inner and outer arms had more synchronous flowering and uniform SS, where the differences in SS were largely a reflection of the timing of flowering of the various inflorescence components and may be an important source of variation in SS within a vine at harvest.
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