Nutrient Status and Growth of Micropropagated Prickly-Pear Cactus (Opuntia albicarpa Scheinvar cv. "Reyna") Plantlets Colonized with Three-Selected Endomycorrhiza Isolates
by Andrés A. Estrada-Luna, and Fred T. Davies Jr.
In a study performed under glasshouse conditions we assessed the effect of three-selected endomycorrhiza isolates on growth and nutrient uptake of micropropagated prickly-pear cactus (Opuntia albicarpa Scheinvar cv. “Reyna”) plantlets. The three isolates tested were ZAC 19 [including Glomus albidum, G. claroides, and G. diaphanum], “Desierto de Sonora” [including Glomus aggregatum, G. deserticola, G. geosporum, G. microagrgregatum, Sclerocystis coremioides, S. sinuosum, Gigaspora margarita, Scutellospora calospora, and S. gregaria], and a pure isolate of G. intraradices. After 7 months of culture in which plantlets were fertilized with the Long Ashton nutrient solution modified to provide 0.65 mM of P, it was found that the ZAC 19 isolate colonized more extensively (54%) the root cortical cells of prickly-pear plantlets compared to the “Desierto de Sonora” and G. intraradices isolates. However, greater growth was obtained when plantlets were colonized by the “Desierto de Sonora” isolate -- 29.80 cm shoot height, 453.53 cm2 total shoot surface and 15.05 y 17.09 g, respectively of shoot and plant dry mass— as compared to the other two. In general, inoculated plantlets had greater values in total shoot surface and root dry mass compared to the non-inoculated plantlets. The mycorrhizal isolates also affected the nutrient content of shoots. Greater concentrations were observed in macro and micro nutrients in plantlets inoculated wit the “Desierto de Sonora” isolate, with exception of Mn that was significantly greater in the control than in the inoculated treatments. Plantlets colonized by G. intraradices and the control had the lowest levels of nutrient content respect to the other treatments. Our results highlight that prickly-pear cactus plantlets may host different mycorrhizal fungi species; moreover, by studying the symbiotic efficiency we were allowed to improve the plant responses. The knowledge on the appropriate management of the symbiosis gives the possibility to use it at practical levels to reduce chemical fertilizer and pesticide inputs in sustainable agriculture systems.