Songklanakarin Journal of Science and Technology (SJST) (Oct 2015)
Endogenous hormonal status in Pummelo fruitlets cultivar Thong Dee: relationship with pre-harvest fruit drop
Abstract
Relationship between endogenous hormonal status with pre-harvest fruit drop in pummelo fruitlets cultivar Thong Dee was studied during January 2013-August 2013. The results indicated that the concentration of IAA in normal and dropped fruitlets tended to decrease gradually during fruit development and the concentration of GA3 in normal and dropped fruitlets increased continually throughout the study. However, the concentration of ABA in normal and dropped fruitlets decreased during fruit development. The concentration of IAA and GA3 in normal fruitlets were significantly higher than those in dropped fruitlets during fruit development, whereas the concentration of ABA in normal fruitlets were significantly lower than that in dropped fruitlets. Consideration of plant growth promoters (IAA and GA3 ) and plant growth inhibitor (ABA) ratio showed that IAA/ABA ratio in normal fruitlets at 6 week, 8 week and 10 week after fruit set were 7.54, 7.99 and 9.42, respectively, which were significantly higher than those in dropped fruitlets (1.81, 3.21 and 3.77, respectively). GA3 /ABA ratio in normal fruitlets at 6 week, 8 week and 10 week after fruit set were 4.54, 5.64 and 25.26 respectively which were significantly higher than those in dropped fruitlets (0.65, 3.10 and 6.71, respectively). Moreover, peel and pulp of normal fruitlets had significantly higher IAA concentration (2.63 and 3.85 mgL-1) than dropped fruitlets (2.07 and 1.45 mgL-1). Peel and pulp of normal fruitlets had also significantly higher GA3 concentration (2.52 and 4.20 mgL-1), whereas peel of normal fruitlets had significantly lower ABA concentration (0.39 mgL-1) than dropped fruitlets (5.28 mgL-1) but ABA concentration in pulp could not be detected either in normal or in dropped fruitlets. For the IAA/ABA and GA3 /ABA ratio measurement, it was found that the peel of normal fruitlets had significantly higher IAA/ABA ratio (6.74) than dropped fruitlets (0.39), whereas the peel of normal fruitlets had significantly higher GA3 /ABA ratio (6.46) than dropped fruitlets (0.38). Therefore, it was concluded that dropped pummelo fruitlets had the lower auxin and gibberellin concentration than those in normal pummelo fruitlets but had higher ABA concentration than that in normal pummelo fruitlets. For the plant growth promoter and plant growth inhibitor ratio, the normal pummelo fruitlets had higher IAA/ABA and GA3 /ABA ratios than those in the dropped pummelo fruitlets. Balance of plant hormones is involved in pre-harvest fruit drop in pummelo cultivar Thong Dee.
