Effects of GA3, NAA and Brassin-like Substance (BS) on Size and Weight of Rambutan Fruit (<I>Nephelium lappaceum</I> L. cv. Rongrian)

Abstract

Plant Growth Regulators (PGRs) have been widely used for increasing the quantity and quality of fruit, but have rarely been examined in rambutan. This study was separated into 3 experiment with the aim to examine the effect of (1) GA₃ (0, 25, 50 and 75 mg/L) (2) NAA (0, 25, 50 and 75 mg/L) and (3) Brassin-like substance (BS)  (0, 0.5, 1.0 and 1.5 mg/L) on size and weight of rambutan fruit. The PGRs were sprayed on rambutan inflorescences at 7-9 weeks after flowering. The fruit were classified for quality level based on Thai Agricultural Commodity and Food Standard (TACFS) by calculation from fruit weight. The result showed that application of 75 mg/L GA₃ gave higher fruit weight and flesh weight than lower rates (25 and 50 mg/L). Application of GA₃ at all rates increased fruit width, flesh thickness, seed length and seed weight over the control but there was no difference among the three GA₃ rates. Application of 25 mg/L of NAA gave a higher flesh thickness than the higher rates (50 and 75 mg/L). Neither GA₃ nor NAA were able to shift fruit quality into level 1 of TACFS. Application of BS increased fruit width, seed length, flesh thickness, peel thickness, fruit weight, flesh weight, and peel weight over the control but there was no difference among the BS rates. However, BS at all rates shifted the rambutan quality to level 1 while the control treatment was classified as level 2 of TACFS. The BS gave a higher capability for increasing fruit length, fruit weight and flesh weight of rambutan over the control treatment than GA₃ and NAA.