Introduction

A frequent response of fruit trees to deficit irrigation (DI) is the promotion of flowering. This flowering promotion is often explained in terms of a lesser resource competition with vegetative growth effectively restrained by water deficit in evergreen and deciduous fruit trees (Chaikiattiyos et al., 1994; Behboudian and Mills, 1997). This tree response to DI has been successfully exploited to induce out of season blooming and to increase the levels of flowering in many tropical and subtropical fruit crops (Barbera et al., 1985; Crane, 2004; Grierson et al., 1982; Whiley, 1993; Stern et al., 1998; Bally et al., 2000), among them loquat (Cuevas et al., 2007).

Loquat (Eriobotrya japonica Lindl.) is a subtropical evergreen fruit tree of the family Rosaceae, subfamily Maloideae that presents an annual cycle reverse to that of the well-known temperate fruit crops. Loquat rests during summer, blooms in autumn, develops its fruit through winter and ripens them in early spring. Its unusual phenology allows growers to obtain high prices for its fruits, especially for early-season harvests. In previous experiences, we have demonstrated that deficit irrigation is a useful strategy to advance harvest date making the crop more profitable (Hueso and Cuevas, 2007).

As occurred in other pomes, loquat blooms apical; in this species forming terminal panicles in current year wood. Apical flowering requires the end of shoot growth before panicle initiation can take place. This occurs in some moment after a period of summer dormancy poorly characterized. New shoot growth become then both support and competitor of flowering. Same flowering habit applies to others tropical and subtropical fruit crops where the management of shoot growth using different techniques has resulted in increasing levels of flowering (Davenport, 2003; Salazar-García and Vázquez-Valdivia, 1997; Stern and Gazit, 1993). Here, we report the effects of different levels of water deficits on shoot growth and flowering and discuss the possible mechanisms involved in the promotion of flowering in response to the imposed water deficit.

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