Gen dan QTL Pengendali Umur pada Kedelai

Traits that control time of flowering and maturity in soybean determine harvesting time of a soybean cultivar. In Indonesia, early maturing soybean cultivars are important at short period growing seasons due to the water shortage in dry planting season. Shorter period of growing season would increase the crop harvest index. Genetic diversity of the present soybean germplasm collection is low. Diversity improvement through introduction from countries with four seasons faced difficulty due to differences in growth adaptability. Technology for developing germplasm with a broader adaptation will facilitate germplasm movement from a more diverse environmental growth. The objective of this review was to describe how the time of flowering and maturity are controlled in soybean. The review is supported by flowering time mechanism of the model plant Arabidopsis thaliana as the genetics of flowering time has been intensively studied in this model plant. Transition from vegetative to reproductive development is the outcome of the activation of genes responsible for floral organ formation. Initial activation is generally the result of environmental cues indicating the appropriate time to flower. Studies from Arabidopsis showed that transition from vegetative to reproductive stage is complex involving many genes and several genetic pathways. In soybean, time of flowering and maturity are controlled by at least nine genes, E1 to E8 and Dt1. The genes interact with daylength and temperature. Major and minor QTLs controlling the traits were identified using various mapping populations. The major QTLs were detected at various populations with diverse genetic backgrounds tested at diverse environmenttal conditions. Some of the QTLs were associated with the E genes and some others were not. Several Arabidopsis flowering gene homologous sequences were also mapped on the soybean genome. The E gene markers and the QTLs with large effect for reproductive traits are breeder targets for breeding and development of soybean photoperiod insensitive germplasm. Genes for flowering time isolated from Arabidopsis can be used to develop transgenic soybean with broader adaptation. Technology for development of soybean germplasm with broader adaptation will facilitate the soybean germplasm movement from diverse environmental growth conditions to support systematic and sustainable national soybean breeding programs.