INVITRO INDUCTION OF HAPLOID, DIPLOID AND TRIPLOID PLANTLETS BY ANTHER CULTURE OF IOCHROMA-WARSCEWICZII REGEL

Pollen of Iochroma warscewiczii Regel (Solanaceae) produced embryogenic calli or embryos inside anthers cultured on Nitsch & Nitsch medium. Two distinct pathways could be recognized in this process, one involving mainly the vegetative cell, and the second starting with two equal cells in the pollen grains. In all media tested, androgenesis initiation was highest when anthers contained pollen at the first mitosis, or close to it, at inoculation. High sucrose (7%) and calcium (11.3 mM) concentrations were found to be highly desirable for the induction of androgenesis in this species. Addition of benzylaminopurine (0.5 mg l-1) to the culture medium seems to slightly improve callus or embryo production. When all three factors were present at optimal concentrations as much as 13.9% of inoculated anthers were found to be embryogenic. Plantlet development from pollen embryos required lower sucrose (3%) and a combination of 0.1 mg l-1 benzylaminopurine and 0.5 mg l-1 gibberellic acid in the culture medium. Cytological analysis of 55 regenerated plantlets showed that about 49% were haploids, but diploid (ca. 49%) and triploid (ca. 2%) plants were also obtained. © 1990 Kluwer Academic Publishers.