EFFECTS OF BIOSTIMULANTS ON FRUITS OF PULASAN [NEPHELIUM RAMBOUTAN-AKE (LABILLARDIERE) LEENHOUTS]

Pulasan (Nephelium ramboutan-ake) is a tropical fruit crop in the Sapindaceae family. Native to Malaysia, pulasan is considered an exotic fruit with potential as a commercial crop in Puerto Rico. Large fruit size and enhanced quality may increase the market value of pulasan. In other fruit crops, biostimulants have been shown to increase yield and/or quality, but there are no reports of biostimulant effects on pulasan. A field experiment was conducted in 2012 in Mayaguez, Puerto Rico, spraying the foliage to run-off with one of four treatments: (1) control plants without exogenous biostimulants, (2) a commercial extract of marine alga Ascophyllum nodosum (Stimplex^TM) (AN) at the rate of 2 L/ha applied every 2 weeks for a total of 7 applications, (3) a commercial mixture of free amino acids and potassium (AminoQuelant K Low pH^TM) (AAK) at the rate of 2 L/ha applied every 2 weeks for a total of 7 applications, and (4) a commercial extract of natural brassinolides from plants (ComCat^TM) (NB) at the rate of 100 g/ha applied every 4 weeks for a total of 4 applications. All the biostimulants were first sprayed 8 weeks after anthesis at rates suggested by the manufacturers. Trees treated with AAK had fruits with the same diameter and weight as control trees, but with lower soluble solid concentration in the pulp. Spraying trees with AN did not affect fruit weight, diameter, and soluble solids concentration in the pulp, but significantly increased seed weight as compared to the check. Trees treated with NB had significantly heavier and larger fruits, with the heaviest pericarps, but with significantly less soluble solid concentration in the pulp than untreated trees.