4.3. Conditions favoring high bud fertility also promote a large number of flowers per inflorescence
Given the existence of a link between bud fertility and flower number per inflorescence through the branching process, it could be hypothesized that conditions promoting high bud fertility also promote high berry number per bunch. The hypothetical boundary line drawn in Fig. 5 tends to confirm this hypothesis: bud fertility and berry number per bunch increase together until reaching a plateau. Therefore, conditions that are very detrimental to bud fertility are also detrimental to berry number per bunch, most probably because of the importance of the branching process for both yield components. Similar results were obtained by Dunn and Martin (2007), in contrast with numerous other studies showing that a small number of inflorescences leads to an increased bunch size through higher number of berries or higher berry weight, in accordance with the well-known trade-off between size and number of organs (Lescourret and Génard, 2003; Sadras, 2007). But as stressed by Dunn and Martin (2007), this is true when manipulating inflorescence number during the current cropping season (seasonFig2) whereas we are also considering here the effects of the previous year (season 1).However, berry number per bunch could be notably reduced(Fig. 5). A poor fruit set or some flower abortion in season 2 may explain this reduction and lead to a small number of berries per bunch and a high bud fertility. This will have to be taken into account in a future framework to analyze the yield formation of grapevine.