Assessment of tepojal as a support medium in in vitro germination of Barkeria whartoniana (Orchidaceae) and subcultures of B. uniflora and B. scandens

Abstract

Objective: We evaluated the use of tepojal as a substitute for bacteriological agar for in vitro culture of three species of Mexican orchids of the genus Barkeria. We had three objectives: (1) evaluate the use of tepojal for the in vitro germination of B. whartoniana seeds; (2) compare the growth and survival of B. uniflora and B. scandens plants in in vitro culture on bacteriological agar and tepojal, and (3) compare the early ex situ survival of the B. uniflora and B. scandens previously cultivated in vitro on bacteriological agar and tepojal. Design/Methodology/Approach: For the growth experiment, 1,050 seedlings of Barkeria scandens and B. uniflora were used. Two types of culture medium were prepared: (1) Liquid with tepojal and 40 % MS medium with dextrose, yeast, coconut water, activated carbon and refined sugar, and (2) solid at 40 %, with the same elements as the liquid one, but with 6 g of bacteriological agar. For the germination experiment of Barkeria whartoniana in tepojal we use seeds from a mature (open) capsule. After disinfection, seeds were sown in tepojal with liquid medium and in a solid (agar) culture using a syringe technique. All the seeds were sown in 100 % p668 MS medium with 100 mL/L of coconut water and 15 g/L of refined sugar and using in both the MS medium. Results: Barkeria uniflora seedlings had a greater growth than in B. scandens regardless of the type of treatment. When comparing within each species, we found that the two treatments (tepojal vs agar) did not produce differences in the growth of the shoot of both species. Roots growth was influenced by both the effect of the species and the treatment, as the longest roots were found in tepojal medium. Seed germination observed in the liquid medium with tepojal was not apparently different from that in agar. In both cases the entire surface of the jar was covered with green protocorms. Findings/Conclusions: Tepojal did function well as a substrate to germinate Barkeria whartoniana, but tests must continue to be carried out to evaluate its effectiveness. As no differences were found for aerial growth between agar and tepojal in Barkeria scandens and Barkeria uniflora, we consider this substrate as a good substitute for agar because it can produce more biomass per gram of culture medium used; therefore, if we consider the costs the use of tepojal is much cheaper and much easier to get.