A phenotypic test for delay of abscission and non-abscission oil palm fruit and validation by abscission marker gene expression analysis

Knowledge of the cell separation processes underlying organ abscission is limited mainly to the eudicot model systems tomato and Arabidopsis, while less is known about the mechanisms in crop species in general, and monocots in particular. Here we describe a simple phenotypic screen for oil palm plant lines with delayed or non-abscising fruit. The phenotypic test was used on the two species of oil palm including Elaeis guineensis and E. oleifera, in addition to their interspecific hybrids, and hybrids backcrossed to E. guineensis. A large variation in abscission phenotypes was observed. Histological analysis revealed similarities and differences in the abscission zone (AZ) of E. guineensis and E. oleifera, and dominant traits were observed in the AZ of the interspecific crosses. The expression of abscission marker genes for a polygalacturonase (EgPG4) and an ethylene synthesis ACO synthase (EgACO) were monitored during abscission of a randomly selected set of plants and in a non-abscising individual identified by the phenotypic test.