Exploring the mechanism of potassium chlorate-induced flowering in Dimocarpus longan

Flowering is the vital stage of plant development since it is the precursor to fruit and seed production as well as the vehicle for genetic improvement by breeding. Understanding flower induction in tree crops is often difficult since trees are a long-term perennial crop that is subject to environmental and cultural changes over multiple seasons of growth. Unlike temperate fruit trees, where growth, dormancy and break of dormancy is determined by the seasons, subtropical and tropical fruit trees rely on more subtle changes in rainfall, temperature or nutrient availability. The discovery of potassium chlorate induced flowering in longan provides an excellent opportunity to investigate the mechanism of flowering in longan. Preliminary experiments suggest that chlorate inhibits nitrate reductase activity in longan trees treated with potassium chlorate, however there is no significant difference in the total nitrogen content and carbon:nitrogen (C:N) ratio in potassium chlorate treated and untreated trees. In addition to potassium chlorate, sodium chlorite and sodium hypochlorite are also able to effectively decrease nitrate reductase activity and induce flowering of longan trees. To identify genes that may be involved in potassium chlorate induced flowering, we created a suppressive subtractive hybridization (SSH) library to longan cDNAs that are differentially expressed in vegetative buds or floral buds induced by potassium chlorate.