Interspecific grafting as an alternative for asexual propagation of Pinus rzedowskii Madrigal & Caball. Del. in danger extinction

Introduction: Pinus rzedowskii Madrigal & Caball. Del. is endemic to Mexico, in danger of extinction and low natural reproduction. An alternative for propagation is interspecific grafting, under the assumption that the phylogenetically more related species positively influence survival. Objectives: To evaluate grafting survival of P. rzedowskii with rootstocks of five Pinus species. Materials and methods: Interspecific grafting of P. rzedowskii with P. pinceana Gordon & Glend, P. maximartinezii Rzed, P. ayacahuite var. veitchii (Roezl) Shaw, P. pseudostrobus Lindl. and P. rzedowskii (control treatment) was carried out. The grafting method was side-veneer graft; grafting was quantified for six months and survival was evaluated using the nonparametric Kaplan-Meier method. Results and discussion: The highest final grafting survival and expected survival function were obtained with rootstocks of P. rzedowskii (85.7 ± 0.21 %; m = 0.97), followed by P. pinceana (80 ± 0.31 %; m = 0.95); P. pseudostrobus had the lowest values (20 ± 0.89 %; m = 0.66). Significant differences (P < 0.0001) were observed between P. pseudostrobus and P. maximartinezii regarding P. rzedowskii a P. pinceana. Conclusion: P. pinceana, a species phylogenetically closer to P. rzedowskii and P. maximartinezii, was the one with the highest survival rate, which may be an alternative for the rescue and ex situ conservation of P. rzedowskii.