Genotype By Environment Interaction and Epistasis of Flowering Time.

Flowering time is a complex trait involved in the adaptation of plants to their local environment. Flowering time in sorghum is controlled by multiple genes. To date, only three of these genes (Ma1, Ma3, and Ma6) have been identified. The objectives of this research are to investigate the genotype by environment (G × E) interaction of sorghum flowering time, and to identify the underlying genes. The experiment was carried out in three years (2011 to 2013) at three locations (Guayanilla Puerto Rico, Manhattan Kansas, and Ames Iowa). Flowering time was measured on a sorghum recombinant inbred line (RIL) population with 250 entries. This RIL population was genotyped using genotyping by sequencing (GBS). A total of 10,370 SNP markers were used for linkage map construction and QTL analysis. Genotypes of high photoperiod sensitivity flowered early in tropical region but significantly late in temperate region. Genotypes of low photoperiod sensitivity, however, flowered late in tropical region but early in temperate region. Two major QTL regulating flowering time were detected on chromosome 6 and 10 in this RIL population. The two QTL show QTL-by-QTL interaction (epistasis). The effect size and direction of each QTL depend on the status of the other QTL. A third QTL on Chromosome 8 was only detected in tropical environment. This QTL likely controls flowering time by responding to the ambient temperature. This study shed light on how plants adapt to their local environments, and how epistasis plays an important role in regulating flowering time in plants.