Source–sink manipulation to increase melon (Cucumis melo L.) fruit biomass and soluble sugar content
Robert L. Long A C , Kerry B. Walsh A , Gordon Rogers A B and David J. Midmore AA Plant Sciences Group, Central Queensland University, Rockhampton, Qld 4702, Australia.
B Applied Horticultural Research, PO Box 552, Sutherland, NSW 2232, Australia.
C Corresponding author. Email: r.long@cqu.edu.au
Australian Journal of Agricultural Research 55(12) 1241-1251 https://doi.org/10.1071/AR04157
Submitted: 8 July 2004 Accepted: 9 November 2004 Published: 21 December 2004
Abstract
Various source–sink perturbations were employed to alter partitioning to orange flesh melon (Cucumis melo L. reticulatus group) and thus to influence fruit biomass and soluble sugar content (indexed as total soluble solids of fruit juice, % TSS), with attention given to the timing of treatment application. A strong relationship existed between harvest index and fruit mass (r2 = 0.88) in control plants, whereas the correlation with fruit TSS was poor (r2 = 0.11). Augmentation of assimilate supply to fruit early in fruit development (before approx. 21 days before harvest, DBH) resulted in more fruit set and increased fruit biomass, whereas augmentation after 21 DBH resulted in increased fruit TSS. Thus, fruit biomass was increased (1644 cf. 1442 g FW per fruit for control, P = 0.02), but not TSS, on plants in which fruit set was delayed (source biomass increased, harvest index decreased from 59% for control to 38%). Treatment of plants with a cytokinin-based vegetative growth inhibitor at 14 DBH produced fruit with higher TSS (11.3 cf. 10.7% for control). Thinning fruit to leave 1 fruit per plant 1 week before harvest increased the proportion of fruit in a population that exceeded a quality control standard of 10% TSS from 20 to 80%. Variations in plant response with timing of treatment application are interpreted in terms of fruit development (cell division, cell expansion, and sugar accumulation phases). Although a detriment to yield (15 cf. 31 t/ha for control), the fruit thinning treatment was recommended for commercial use and a simple model was developed to calculate the required farm-gate price of fruit to make thinning economically viable.
Additional keywords: rockmelon, cantaloupe, fruit quality, fruit thinning, pollination scheduling, total soluble solids.
Acknowledgments
Financial support was provided by The Harvest Co. and Horticulture Australia Limited through the ‘Sweet Melon’ project. We gratefully thank Robert Gray of The Harvest Co. for promoting this line of work, and we thank melon growers Bluey Stoldt, Peter Dodson, and Phil Mansell for their patience with field experiments.
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