IN VITRO PRODUCTION OF LIQUID WAX OF JOJOBA (SIMMONDSIA CHINENSIS) VIA ASEXUAL EMBRYOS

YI-CHANG WANG, Purdue University

Abstract

Immature zygotic embryos of jojoba, cultured on a semisolid basal media supplemented with 1 mg/liter 2,4-dichlorophenoxyacetic acid (2,4-D), initiated asexual embryos from callus. Asexual embryos were initiated from single cells on the periphery of the callus and passed through typical embryogenic stages. The initiation of asexual embryos from immature zygotic embryos cultured in media containing 1 mg/liter 2,4-D was optimum at the 3-4 mm stage, in light, pH 5.7, 25$\sp\circ$C, and 6% sucrose. Embryogenic callus maintained on a medium containing 40 mg/liter sodium bisulfite as antioxidant and 1 mg/liter 2,4-D, continued to proliferate asexual embryos but embryos remained in an arrested state of development until 2,4-D was withdrawn. Zygotic embryos, containing about 50% "liquid" wax at maturity (about 800 mg dry weight), accumulated liquid wax in vivo from the very immature stage (10 mg dry weight) with consistent quality based on the proportion of C36-C46 esters. Immature zygotic embryos cultured in the basal medium without 2,4-D up to 10 weeks, the duration of the experiment, grew and accumulated wax of similar quality to wax produced in vivo. The optimal sucrose concentrations for both growth and wax accumulation were 15% (w/v) for semisolid medium or 9% (w/v) for liquid medium. Immature zygotic embryos grew better but accumulated less wax in the liquid than on semisolid media. Immature zygotic embryos (initial dry weight 1.6 mg) cultured on 15% sucrose semisolid media for 10 weeks, averaged 60 mg dry weight and produced 40.4% wax, an efficiency similar to that of zygotic embryos grown in vivo. Asexual embryos when cultured in liquid or semisolid media with sucrose varying from 3-21%, grew and accumulated wax of similar quality to in vivo -produced wax up to 8-12 weeks, but wax accumulation declined at week 16 when the experiment terminated. The optimal sucrose concentrations for growth and wax accumulation were 9-15% sucrose in semisolid media and 3% sucrose in liquid media. Asexual embryos grew better and accumulated more wax on semisolid than in liquid media at sucrose concentrations above 3%. Asexual embryos, unlike zygotic embryos in vitro, did not respond to high sucrose concentrations when cultured in liquid media. Asexual embryos (initial dry weight 0.33 mg) cultured on 9% sucrose semisolid media for 12 weeks, grew to an average of 92 mg dry weight, 75% of zygotic embryos in vivo of the same embryo dry weight, with 17.6% wax based on dry weight.

Degree

Ph.D.

Subject Area

Plant propagation

COinS