Effects of GA₃₊₄ and GA₄₊₇ Application Either Alone or Combined with Prohexadione-Ca on Fruit Development of Japanese Pear ‘Kosui’

Abstract

In order to promote increases in the size of 'Kosui' Japanese pear [Pyrus pyrifolia (Burm.) Nakai] fruit by plant growth regulators, we applied gibberellin (GA) 3+4 paste [2.7% (w/w), A 3 :A 4 = 90:10] in combination with prohexadione-calcium [1%, PCa; BAS-125 (3-oxido-4-propionyl-5-oxo-3-cyclohexene-carboxylate)], an inhibitor of GA 2β-hydroxylation that catabolizes active GA into an inactive form, to fruit pedicels at approximately 30 days after full bloom. GA 3+4 +PCa treatment advanced fruit growth only in the early stages, but fruit weight did not show any significant differences between the untreated control and GA 3+4 +PCa-treated fruits at harvest. In contrast, when GA 4+7 [2.7% (w/w), A 4 :A 7 = 66:34] was applied, the fruit weight at harvest was greater than that of untreated fruit. Moreover, GA 4+7 treatment in combination with PCa resulted in an even higher fruit weight at harvest. The GA 4 concentration in fruit flesh was not affected by GA 3+4 application at 1 week after the treatment (WAT) either with or without PCa, but GA 4 levels increased with GA 4+7 +PCa treatment, resulting in a significant increase in fruit weight at harvest. A single GA 4+7 application almost doubled the GA 4 concentration compared with the untreated control, but the difference was not significant. These results indicate that fruit weight at harvest was greater when the GA 4 concentration was higher in the fruit flesh at 1 WAT. The higher concentration of GA 4 in the GA 4+7 +PCa-treated fruit compared with the GA 4+7 treatment alone may be attributed to the function of PCa that acts to prevent the inactivation of GA 4 to GA 34 by inhibiting 2β-hydroxylation.

Endogenous Auxin Content Contributes to Larger Size of Apple Fruit

“…For example, the application of CPPU, an artificial-synthesized cytokinin, increased fruit size in kiwifruit ( A. chinensis ) by inducing cell number ( Cruz-Castillo et al, 2002 ). Gibberellin treatment increased the fruit size of pear ( P. pyrifolia ; Ito et al, 2015 ) and apple ( Martin et al, 1970 ). However, in this study, we did not find DEGs belong to cytokinin or gibberellin synthesis genes ( Supplementary Table 3 ).…”

“…For example, the application of N1-(2-chloro-4-pyridyl)-N3-phenylurea (CPPU), an artificial-synthesized cytokinin, increased fruit size in kiwifruit (Actinidia chinensis) by inducing the cell number (Cruz-Castillo et al, 2002). Gibberellin treatment increased the fruit size of pear (Pyrus pyrifolia; Ito et al, 2015) and apple (Martin et al, 1970). Auxin has been reported to affect the fruit size in many tree fruits, for example, exogenous auxin treatment increased fruit size by increasing cell size in apple (Devoghalaere et al, 2012).…”

Prohexadione-Calcium Application during Vegetative Growth Affects Growth of Mother Plants, Runners, and Runner Plants of Maehyang Strawberry

“…Pro-Ca is a gibberellin (GA) biosynthesis inhibitor, which is the co-substrate for dioxygenases catalyzing hydroxylations involved in the late stages of GA biosynthesis. The main target of Pro-Ca seems to be 3β-hydroxylase, an enzyme that catalyzes primarily the conversion of inactive GA 20 /GA 9 into highly active GA 1 /GA 4 in either the early 13-hydroxylated pathway or the early non-13-hydroxylation pathway, respectively [11][12][13]. Reducing plant height is an important effect of PGR application, leading to increased quality and yield, and decreases in cost, space, and labor [13,14].…”

“…The main target of Pro-Ca seems to be 3β-hydroxylase, an enzyme that catalyzes primarily the conversion of inactive GA 20 /GA 9 into highly active GA 1 /GA 4 in either the early 13-hydroxylated pathway or the early non-13-hydroxylation pathway, respectively [11][12][13]. Reducing plant height is an important effect of PGR application, leading to increased quality and yield, and decreases in cost, space, and labor [13,14]. Pro-Ca has been shown to reduce and regulate the growth of crops such as petunia, impatiens, rice, chrysanthemum, pear, and various vegetables without the negative effects of decline in fruit quality and yield [8,[13][14][15][16].…”

“…Reducing plant height is an important effect of PGR application, leading to increased quality and yield, and decreases in cost, space, and labor [13,14]. Pro-Ca has been shown to reduce and regulate the growth of crops such as petunia, impatiens, rice, chrysanthemum, pear, and various vegetables without the negative effects of decline in fruit quality and yield [8,[13][14][15][16]. Most studies on the influences of Pro-Ca have focused on seed-propagated crops, but there are few reports on the application of Pro-Ca to vegetatively-propagated crops [16][17][18].…”