There are more than 30 species of Cyrtopodium distributed in south-most Florida and Central and South America (Pridgeon, 1998). The generic name Cyrtopodium means “curved little foot” for the shape of the column in the center of the flower. Cyrtopodium plants such as Cyrtopodium cardiochilum have been used for anti-inflammatory purposes and puncture wounds by Brazilian inlanders but are threatened by urbanization in Brazil (Barreto and Parente, 2006; Menezes, 1995a, 1995b). Cyrtopodium paranaense is a tropical terrestrial species with thick pseudobulbs and racemes that rise from the developing shoot. In its natural propagation, C. paranaense is mainly through sexual (i.e., gene recombination) pollinated seed germination. Culture media for growth of seed-derived protocorms in C. paranaense have been surveyed (Rego-Oliveira and Faria, 2005). However, there are no reports on vegetative protocorm-like body (PLB) induction or in vitro regeneration of C. paranaense.
A variety of explants have been used in many laboratories for clonal propagation of orchids, producing millions of low-cost orchid plantlets throughout the world (Chen and Chang, 2006; Chugh et al., 2009; Ernst, 1994; Park et al., 2003; Teng et al., 1997). However, a number of problems have restricted the choice of explants, including phenolic exudation, limited numbers of meristems, the difficulty to induce PLBs, and somaclonal variation (Chugh et al., 2009; Sánchez, 1988). Although root tips of orchids are considered recalcitrant as explants in tissue culture, the formation of PLBs by embryogenesis occurs in certain orchids such as Oncidium and Doritaenopsis (Kerbauy, 1984; Park et al., 2003).
In the present study, we investigated the effects of indole-3-acetic acid (IAA) and thidiazuron (TDZ) on inducing PLB formation from excised root tips of aseptically grown seedlings of C. paranaense. The root tip–PLB conversion was monitored through histological sections at different developmental stages.
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