IMPROVING FLOWERING OF LONGAN AND LYCHEE TREES IN HAWAII
Tropical Plant Genetic Resources and Disease Research
2011 Annual Report
1a.Objectives (from AD-416)
1) Optimize chlorate-induced flowering & fruit production in longan;.
2)Determine the long-term effect of chlorate application on longan fruit quality;.
3)Determine floral induction for "Kaimana" Lychee;.
4)Evaluate new lychee cultivars for Hawaii; and.
5)Stimulate off-season flowering of lychee.
1b.Approach (from AD-416)
1) Foliar applications of alternative chemicals to chlorate will be evaluated & fruit thinning experiment will be conducted;.
2)Soil chlorate levels, plant nutrition, flowering & fruit quality will be evaluated on longan tree after repeated application of chlorate;.
3)Artificial cool temperatures will be used to determine floral induction for "Kaimana" lychee;.
4)Molecular markers will be used to identify lychee that flower & fruit in Hawaii; and.
5)Grafting experiments will be used to transmit floral stimuli from longan to lychee and between lychee cultivars with different floral initiation requirements. (Documents Trust agreement with UH Hilo. 425 log 31540). Formerly 5320-21000-009-07T (09/2008).
This agreement was established in support of Objective 3 of the parent project, the goal being to characterize and evaluate tropical fruit genetic resources for priority traits, such as flowering and fruiting.
This is the final report for the project 5320-21000-012-01T which will terminate in August, 2011. Chlorate treatments in longan commonly induce flowering in 90 to 100% of terminals which require fruit thinning when fruits are 6-12 mm in diameter. Fruit thinning is a labor intensive process consisting of removal of 1/2 to 2/3 of each panicle. Sequential applications of foliar fertilization during fruit development and hand thinning of fruiting panicles on two longan cultivars, ‘Egami’ and ‘Biew Kiew’ were compared. In the heavier bearing ‘Egami’ cultivar, the incidence of fruit cracking and unmarketable under-sized fruits was greater in the foliar fertilized trees compared to hand thinned tree. Postharvest quality including aril firmness and disease incidence was also more severely affected in the fruits from the foliar fertilized trees compared to the hand thinned trees. The foliar fertilization treatment was comparable to hand thinned fruiting panicles in the lesser bearing ‘Biew Kiew’ cultivar, and fruit quality was retained even after storage for 14 days. Fruits from the chlorate treated trees were also provided to researchers for additional post-harvest packaging treatments to determine the best packaging material on longan quality.
Flowering locus T (FT) is a gene involved in flowering, originally identified in model system Arabidopsis. Equated to the classic physiological flowering signal florigen; the FT protein is produced in leaves and translocated into the meristem where it initiates the transition from vegetative to floral growth. Using degenerative PCR primers we have isolated three full length FT orthologs from longan and the 5’ end of four FT orthologs from lychee. From Southern blot analysis, we estimate that there may be five FT genes in longan and four or five genes in lychee. Semi-quantitative polymerase chain reaction (PCR) suggest that the FT genes in longan are less abundant in leaves from chlorate treated trees 12 to 24 days after chlorate treatments compared with non-treated trees. Temperature regulation has not been determined due to low floral induction conditions present in Hawaii during the winter of 2010 to 2011. The lead scientist monitored progress through site visitations, individual meetings with growers, and presentations at the Hawaii Tropical Fruit Growers annual meeting.