EFFECTS OF AN ANTI-GIBBERELLIN GROWTH RETARDANT ON GROWTH RESPONSES OF POTATO NODAL STEM SEGMENTS CULTURED IN VITRO

Foliage of non-induced `Katahdin' potato plants was treated with BAS-111. Other plants were sprayed with GA3 solution and placed in an inducing chamber. All treatments were repeated the following week. After final treatment, apical, sub-apical, medial, and basal nodal stem segments were taken from each plant, surface-sterilized, and placed on MS culture media. After 3 weeks in a darkened incubator, cultures were examined. Induced plants produced 5.5 times more tubers than did non-induced segments. BAS-111 applied to non-induced plants was associated with 63% reduction in rhizome length and 3.2-fold increase in tuber number. GA treatment to induce plants resulted in improved rhizome elongation, delayed and reduced tuberization when compared with control explants. Lower nodes produced more and larger tubers than did younger tissues. Results will be discussed in light of current literature.

Conservation of Citrus Germplasm in Vitro

A study was conducted to evaluate the potential of in vitro techniques for genetic conservation of citrus. A tissue culture system was developed using explants of juvenile `Pineapple' sweet orange. It consisted of: a) establishment of primary cultures from nodal stem segments followed by the recovery of plants in vitro; and b) successive cycles of secondary cultures consisting of the culture of nodal stem segments from in vitro-grown plants, rooting of shoots obtained from nodal stem segments, and recovery of whole plantlets. Two parameters, K and K', based on the multiplication factors of the different stages of primary and secondary cultures are proposed to monitor the system as a potential tool for genetic conservation of citrus. The system also can be successfully used for the conservation of juvenile tissues of two sweet orange varieties [Citrus sinensis (L.) Osb.], trifoliate orange [Poncirus trifoliata (L.) Raf.], Mexican lime [C. aurantifolia (Christm.) Swing.], and `Eureka' lemon [C. limon (L.) Burro. f.]. Chemical names used: 6-benzylaminopurine (BA); α- naphtbaleneacetic acid (NAA).