Mycorrhizal inoculation and phosphorus fertilization show contrasts on native species of the Brazilian Atlantic Forest and Cerrado

ABSTRACT Restoration of degraded sites by using native plants like Plathymenia reticulata Benth. and Melanoxylon brauna Schot. is advisable. However, seedlings of both species, when raised on commercial substrates, may present low survival. This study aimed to evaluate the growth of seedlings under inoculation with arbuscular mycorrhizal fungi (AMF). The seedlings were raised on soil sampled from near an adult plant of the same species. The P. reticulata and M. brauna seedlings were grown with or without the inoculation of a mix of three species of AMF (Rhizophagus clarus, Claroideoglomus etunicatum, and Gigaspora albida), and five doses of P (0, 50, 150, 300, and 450 mg dm-3 of P). All seedlings were inoculated with Bradyrhizobium sp., isolated from each species. After 90 days, P. reticulata inoculated with AMF showed higher growth and nutrient content than those uninoculated, and the maximum plant growth was obtained when received 160 to 280 mg dm-3 of P. On the other hand, no effects of AMF inoculation or phosphate fertilization were observed on M. brauna. For both species, no effect of inoculation was observed on mycorrhizal colonization, and M. brauna, unlike P. reticulata presented a considerable number of nodules. We conclude that inoculation with AMF and P fertilization improves the growth of P. reticulata seedlings but does not promote the growth of M. brauna; presenting the necessity to investigate each species.摘要：采用巴西阔荚合欢（Plathymenia reticulata Benth.）与巴西黑黄檀（Melanoxylon brauna Schot.）等本土植物修复退化场地，是较为适宜的修复途径。然而，若将这两个物种的幼苗培育于商业基质中，其成活率往往偏低。本研究旨在评估接种丛枝菌根真菌（arbuscular mycorrhizal fungi, AMF）对幼苗生长的影响。试验所用幼苗均培育于采自同种成年植株周边的土壤中。试验采用双因素处理设计：其一为丛枝菌根真菌接种处理，设置接种由3种丛枝菌根真菌（近明球囊霉（Rhizophagus clarus）、地表类球囊霉（Claroideoglomus etunicatum）、白色巨孢囊霉（Gigaspora albida））组成的混合菌剂与不接种两个水平；其二为磷肥施用处理，设置0、50、150、300、450 mg dm⁻³共5个施用梯度。所有幼苗均接种了从各自物种根系分离得到的慢生根瘤菌（Bradyrhizobium sp.）。培育90天后，接种丛枝菌根真菌的巴西阔荚合欢幼苗，其生长指标与养分含量均显著高于未接种组；当磷肥施用量为160~280 mg dm⁻³时，该物种幼苗的生长达到峰值。与之相反，丛枝菌根真菌接种与磷肥施用均未对巴西黑黄檀幼苗的生长产生显著影响。就两个物种而言，丛枝菌根真菌接种均未对菌根侵染率产生影响；且与巴西阔荚合欢不同，巴西黑黄檀幼苗可形成数量可观的根瘤。综上，接种丛枝菌根真菌配合磷肥施用可显著促进巴西阔荚合欢幼苗的生长，但对巴西黑黄檀幼苗的生长无明显促进效果，这表明针对不同物种分别开展针对性研究具有必要性。