Role of naphthalene acetic acid and phenothiol treatments on increasing fruit size and advancing fruit maturity in loquat

Loquat trees (Eriobotrya japonica Lindl cv. Algerie) were treated with naphthalene acetic acid at 25, 50 and 100 mg l(-1) (NAA-25, NAA-50 and NAA-100) and phenothiol at 50 mg l(-1) when fruit were at 50 and 30% of their final size in the experiments carried out in 2001 and 2002, respectively. The effect of these synthetic auxin treatments on yield, fruit size, precocity and some variables related to fruit quality was analysed. Total production was significantly increased by phenothiol, NAA-25 and NAA-50 treatments with respect to control trees, due to an increase in fruit size, whereas total yield per tree decreased in NAA-100 treated trees. A significant delay in maturity of loquat fruit from phenothiol and NAA treated trees was observed when treatments were applied at 50% of final fruit size (2001 season). However, when the auxin treatments were applied at 30% of final fruit size (2002 season) loquat fruit precocity increased. Physico-chemical variables related to fruit quality, such as colour, firmness, ripening index, and sugar and organic acid content were similar in loquat fruit picked at commercial maturity from control and treated trees. Thus, these treatments accelerated fruit growth and maturation, without any undesirable effect on nutritive and organoleptic properties of loquat fruit, and also increased both fruit size and total yield per tree, allowing for an increase in its economic value. (C) 2004 Elsevier B.V. All rights reserved.