Title: Optimization of lychee and longan flowering and fruiting in Hawaii. Authors
Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 8, 2008
Publication Date: N/A
Technical Abstract: A new management method was developed for consistent flowering and fruiting of ‘Kaimana’ lychee at the Inconsistent or lack of flower and fruit production in germplasm accessions is a major obstacle in the evaluation, characterization and documentation of germplasm accessions and limits the genetic cultivars that can be used in Hawaii. The discovery that potassium chlorate (KClO3) application to the root zone of longan, Dimocarpus longan, trees induces flowering regardless of genotype and season, provided an ideal opportunity to evaluate this unique flower inducing treatment and to determine its molecular mechanism so it might be used for germplasm improvement. In Hawaii, application of chlorate, chlorite and hypochlorite chlorite and hypochlorite (bleach) induced off-season longan flowering is similar to chlorate treated trees. Chlorate, chlorite and hypochlorite application reduce levels of nitrate reductase two weeks after application of chlorate to longan trees in the field. Hypochlorite induction of flowering with bleach was likely due to chlorate in the bleach solution. Chlorate was present in the leachate from potted longan trees treated with bleach and was detected in bleach prior to soil application. The quantity of chlorate found in bleach induced flowering to the same or greater extent as equivalent quantities of potassium chlorate suggesting chlorate is an active ingredient responsible for longan flowering. In addition, sixty-five unique gene sequences have been identified from a cDNA library enriched for differentially expressed genes in either floral or vegetative buds of Dimocarpus longan. Sequence homology suggest some of these clones have potential regulatory roles in plants and other organisms and represent novel genes not previously associated with flowering. In Hawaii, consistent lychee production is achieved through a combination of management practices that limit high nitrogen content and new vegetative flushes during the time of year when cooler temperatures induce flowering and the utilization of ‘Kaimana’ lychee which was selected in Hawaii based upon its high fruit quality and capacity to flower under Hawaii’s mild winter climate. A protocol consisting of pruning and foliar fertilizer was developed to 1) provide consistent levels of nutrients to the trees; 2) reduce reliance on fertilizer availability dependent upon rainfall; and 3) limit the amount of residual fertilizer held in the soil. Preliminary experiments utilizing this pruning and foliar fertilizer protocol to synchronize and condition ‘Kaimana’ lychee trees were resulted in over 100 lb fruits per tree per year for the two consecutive seasons. Modification of foliar application date resulted in extension of the lychee harvest season.