Adaptation of Long Juvenile Soybean to the Tropics: A Case Study in Indonesia

Abstract The world’s most significant source of protein and oil is soybean, a major legume crop native to temperate regions. In Indonesia, soybean is a national strategic commodity next to maize and rice. Cultivation of introducing long juvenile (LJ) soybean genotypes may prolong the vegetative phase and increase yield under short-day conditions in the tropics. This article reports the genetic control of LJ traits and adaptation of LJ soybean in the tropics with a case study in Indonesia. The molecular mechanism of flowering and maturity should be understandable to improve the adaptability of soybean plants in different latitudes and environments. A short day and genetic variation at maturity genes contribute to adaptation to environments with different photoperiods. Even though genetic control of the LJ trait remained ambiguous, a single recessive gene is known to control the LJ trait. The major classical locus conferring the LJ character, known as J, promotes flowering under short days. The e 9 and other major alleles ( E1-E4 ) could also be useful as an LJ allele, which causes late flowering under short-day conditions in low-latitude tropical regions. A number of soybean genotypes with LJ traits were introduced to Indonesia, and have been used for parental lines using marker-assisted backcrossing and adaptation assay to enhance soybean yield in Indonesia. Since important components in controlling flowering time and maturity have been detected in soybean, the chance of soybean adaptation to tropical regions, including Indonesia, will be easier and higher.