Strategies to improve poor seed germination in Stevia rebaudiana, a low calorie sweetener

Abstract

Expanding cultivation of exotic ‘stevia’ in mid- and low-hill areas of Himachal Pradesh, India, is difficult because of the problem of low seed fertility. The objectives of the present study were to devise strategies to produce fertile seed. Two distinct compatible morphotypes were isolated, which when used in pollination produced fertile seeds, whereas self-pollination always resulted in sterile seed set, indicating sporophytic self-incompatibility in the species. To obtain fertile seeds, a mixed population of compatible genotypes should be raised. Although sporophytic chromosome numbers ranging from 22 to 70 are reported in literature, both the morphotypes investigated had only 22 chromosomes but differed on the basis of leaf shape, shoot collar diameter, plant type (compact or loose) and stevioside/rebaudioside A content.   Key words: Stevia rebaudiana, chromosome number, pollination, stevioside, rebaudioside A.