Brazilian forest ecosystems carry ubiquitous and rare species of arburcular mycorrhiza fungi (AMF). The method of spore morphology underestimates AMF diversity in forest ecosystems. The AMF are not specific to host-plant but to the environments where plants grow. Ubiquitous AMF species may be a source of AMF inocula for forests.
The Australian species Melaleuca alternifolia Cheel. has a strong commercial importance due to the extraction of essential oils from its leaves used in the cosmetic and pharmaceutical industry. In order to obtain an efficient plant production system of M. alternifolia the mini-cuttings technique and the clonal mini-garden management in the productivity and rooting of mini-cuttings and different substrate compositions were analyzed during all the seasons. Mini-stumps derived from cuttings and grown in pots (2 L), were submitted to successive harvesting of their sprouts during the four seasons (september/2013 to august/2014). From the mini-stumps sprouts mini-cuttings were produced, wich were were planted in plastic tubes and kept in a greenhouse for 45 days. Six substrates were used for planting the mini-cuttings: commercial substrate (S1); substrate composed of 100% carbonized rice husk (CRH) (S2); substrate composed of 100% coconut fiber (CF) (S3); substrate composed of 50% CF and 50% CRH (S4); substrate composed of 30% CF and 70% CRH (S5); substrate composed of 70% FC and 30% CRH (S6). The high survival of mini-stumps (over 90%) and the mini-cuttings production (282 mini-cuttings.m-2.month-1) in the shade house demonstrate the technical feasibility for the species, being summer the most appropriate time to collect propagules. The substrate composed by 70% CF + 30% CRH (S6) shows superior results for vegetative propagation of M. alternifolia (91.7% of rooted mini-cuttings), as the single one to contemplate simultaneously all parameters. Summer is recommended as the best time for rooting of mini-cuttings.
Eucalyptus benthamii is a tree species commonly planted in subtropical areas, including the Southern Brazil, due to its tolerance to low temperatures and frosts. The success of E. benthamii plantation depends on the seedlings vigor during transplantation. We hypothesized that improvement of chemical and biological properties of growth substrate would produce more vigorous E. benthamii seedlings. Thus, we applied increasing doses (0, 0.5, 1.0, 1.5 and 2.0 g per seedling) of the organic fertilizer Bacsol, which carries a consortium of potential plant growth promoting microorganisms, on the substrate, and measured the growth and development of E. benthamii seedlings. Two experiments were performed in 2011 and 2012. The first experiment included measurements in four growth stages to estimate the relative growth rates. The second one ended at the time that seedlings reached standard heights for transplantation (about ± 20 cm). Measurements on plant height, stem diameter, shoot dry weight and relative growth rates indicated that the application of Bacsol improved E. benthamii seedlings vigor and decreased the time needed in nursery, from 150 days to 90 days. The best responses occurred at doses from 1.3 g to 1.5 g per seedling. The data demonstrated that application of Bacsol in substrate is a promising technology to increase E. benthamii seedlings vigor.
Black wattle (Acacia mearnsii De Wild.) is a tree legume native to southeast Australia, but present in all continents. Today it covers about 142,400 ha in Brazil, with plantations concentrated in the southern region of the country. Black wattle may form nodules and establish rhizobial symbiosis capable of fixing N 2 , but rhizobial inoculation is not done in commercial plantations. About 40 kg ha −1 of urea is applied during seedling transplantation. In this review, evidences by which rhizobial inoculation affects monoculture, mixed cultivation, and agroforestry black wattle production systems were searched in literature. Previous measurements in cultivated forests have indicated that biological nitrogen fixation in black wattle may provide up to 200 kg of N ha −1 year −1 to the soil. Therefore, rhizobia inoculation may bring several opportunities to improve black wattle production systems. Black wattle is not a very selective partner in the rhizobial symbiosis, but the genus Bradyrhizobium dominates the rhizobial diversity of black wattle nodules. Investigation on rhizobial diversity in soils where the crop is cultivated may represent an opportunity to find more effective rhizobia strains for inoculants. The successful history of biological nitrogen fixation in grain legumes must inspire the history of tree legumes. Microbiology applied to forestry must overcome challenges on the lack of trained professionals and the development of new application technologies.
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