Callus Type, Growth Regulators, and Phytagel on Indirect Somatic Embryogenesis of Coffee (Coffea arabica L. var....

Coffee is a crop of global relevance. Indirect somatic embryogenesis has allowed plants of different coffee genotypes to be massively regenerated. The culture medium composition can affect the calli characteristics that are generated and their ability to form somatic embryos. This research aimed to determine the influence of the type of callus, growth regulators, and phytagel concentration on the embryogenic capacity of the Colombia variety. Leaf explants were cultured on Murashige and Skoog medium with 2,4-dichlorophenoxyacetic acid (2,4-D) (0.5-1.0 mg L^-1), benzylaminopurine (BAP, 1.0 mg L^-1), and phytagel (2.3-5.0 g L^-1). The explants generated two types of calli: friable (beige, soft, watery, easy disintegration, polyhedral parenchyma cells) and compact (white, hard, low water content, difficult disintegration, elongated parenchyma cells). About 68% of the total callus generated was compact; this type of callus produced a greater number of embryos (71.3) than the friable one (29.2). The number of differentiated embryos was significantly affected by the concentration of phytagel; higher concentrations (5.0 g L^-1) resulted in larger quantities (73.7). The highest number of embryos (127.47) was obtained by combining 1.0 mg L^-1 2,4-D, 1.0 mg L^-1 BAP, 5.0 g L^-1 phytagel, and compact callus.