Tectona grandis L.f., known as teak, is one of the most valuable tropical hardwood species that has been extensively planted in tropical zones, covering about 6,8 million hectares (Kollert and Kleine 2017). Recent advances in silvicultural management and use of improved clones have enhanced productivity and wood quality of teak plantations in Brazil. However, the incidence of diseases has increased over time being a threat to sustainability of commercial teak plantations. Therefore, forest pathology studies have been conducted in Brazil to minimize the risks of losses caused by the diseases on teak, ensuring the expected economic profitability. In a recent disease survey conducted in Midwest of Brazil, almost one thousand teak trees showing typical die-back symptoms with root collar rot were found. The diseased trees showed undersize leaves displaying yellowish to pale brown color, followed by wilt, defoliation and death. At the base of the trunk, root collar rot was observed, with sloughing and deterioration of the bark exhibiting flattened and encrusted fungi fruiting bodies of gray to bright white color. Over the time, the wood of infected trees develops black zone lines and soft tissue due to both lignin and cellulose decay. The disease begins in the root and spreads to the collar of the tree, causing a collapse in sap flow leading to mortality. To discover the disease cause, samples of infected trees were collected to perform an accurate pathogen identification by polyphasic approach, as well as pathogenicity test. From isolation in Malt Extract Agar (MEA), one fungus showing white progressing to gray mycelial growth was consistently isolated. Two isolates named as GFP131 and GFP132 were characterized. Microscopic examination showed conidia aseptate, hyaline, ovoid to fusiform-ellipsoid shaped, measuring 6-8 x 2-4 μm; stromata with surface brown to dark brown; perithecia with variable shapes and ostioles papillate; and ascospores aseptate, dark brown, fusiform to ellipsoid, measuring 20-37 × 8-15 μm, displaying a straight germinal line slightly less than ascospore length. These morphological characteristics were similar to descriptions for genus Kretzschmaria (Rogers and Ju 1998; Stadler et al. 2013). Genomic DNA was extracted from mycelium, and the internal transcribed spacer (ITS) region of rDNA with primer pair ITS1/ITS4 was sequenced and then deposited under Genbank codes MH481853 and MH481854. A BLASTn search showed >99% identity with K. zonata sequence (KY660541). Phylogenetic inference by Maximum Likelihood method using Kimura 2-parameter model confirms that the isolates belong to Kretzschmaria zonata (Lév.) P.M.D. Martin. A pathogenicity test was established in a greenhouse with controlled conditions of temperature (28-30 °C) and humidity (80-90 %). Five plants were inoculated with GFP132 at the collar region with one mycelium disk of approximately 5 mm in diameter each, and the inoculated area was wrapped in plastic film. Disks of MEA culture media were placed on five additional plants as controls. Forty days after inoculation, all of the previously mentioned symptoms were observed for all inoculated plants, while control plants showed only scars at the inoculation point. The pathogen was reisolated from all five of the inoculated plants. Kretschmaria zonata has been reported on teak in Nigeria (West 1938) and in Mexico (Cibrian Tovar et al. 2014). However, this is the first report of K. zonata on T. grandis for Brazil and the first report anywhere to include Koch's postulates, proving the etiology of the disease.
The Tectona grandis L.f. (teak) is an important forest species with high economy value in Asia, Africa, and Latin America. In Latin America, Brazil is one of the countries with the most cultivated areas. The cultivation of teak turns out to be challenging because of its high nutritional demand and the need for seedling production by clonal propagation that includes about 90 days in the nursery phase. The optimization of seedling production is necessary for better results in the nursery and to enhance growth in the field. In this way, the well-known advantage of using microorganisms that promote plant development appears as a potential biotechnological approach to be explored and for the implantation of new areas of wood production. In this study, the inoculation of Bacillus subtilis as plant growth-promoting rhizobacteria (PGPR) was evaluated, and Rhizophagus clarus, an arbuscular mycorrhizal fungus (AMF), and the co-inoculation of these microorganisms in the teak seedling production phase can improve the development of commercial plantations under field conditions. Experiments were carried out under greenhouse and field conditions to evaluate four treatments based on the substrate inoculation of the seedlings. Treatments consisted of a non-inoculated control, PGPR inoculation, AMF inoculation, and PGPR + AMF inoculation. The results of the biometric evaluation of seedlings in the greenhouse showed that there was a significant difference in AMF inoculation and PGPR + AMF inoculation in terms of the specific root length and root density treatments, there was also a positive correlation between these two treatments and the absorption of some nutrients, such as P, N, K, Mg, Cu, Mn, and Zn. This response led to an increase between 4.75 and 11.04% in the field growth rate.
A demanda pela madeira de mogno africano (Khaya ivorensis) é crescente, visando suprir o setor de produtos serrados. Para atender ao mercado madeireiro, a aptidão tecnológica das espécies, geralmente é verificada através da avaliação das suas características inerentes. O objetivo deste trabalho foi quantificar ao longo do tronco, os extrativos, lignina e a massa específica básica dessa espécie. O material analisado foram quatro árvores provenientes de um plantio homogêneo de 10 anos, localizado em Mato Grosso. As subamostras foram retirados nas porcentagens de 0, 25, 50, 75 e 100% da altura comercial das árvores. As análises químicas tiveram como referência as normas da ABTCP (1974) e os ensaios físicos, as normas da ABNT/NBR 11941-02 (2003). Na quantificação de extrativos, a água fria apresentou a menor média (3,91%) e o hidróxido de sódio a maior (20,57%). O teor médio de lignina foi de 30,29% e a massa específica média foi de 0,530 g cm-³. Os dados foram analisados com base na análise de variância, teste de médias e componentes principais (ACP). Concluiu-se que a madeira estudada apresentou características tecnológicas compatíveis para ser utilizada na área moveleira, e também em construções externas, mostrando potencial competitivo para atuar no setor.Palavras chave: extrativos; lignina; massa específica básica; qualidade de madeira. CHEMICAL AND PHYSICAL CHARACTERISTICS OF AFRICAN MAHOGANY WOOD (Khaya ivorensis A. Chev.) ABSTRACT: Demand for African mahogany (Khaya ivorensis) wood is increasing to supply the sawn timber sector. To cater to the timber market, the technological suitability of the species is generally verified by assessing their inherent characteristics. The objective of this work was to quantify along the trunk the extractives, lignin and the basic specific mass of this species. The analyzed material were five trees from a homogeneous planting of 10 years, located in Mato Grosso. The subsamples were taken in percentages of 0, 25, 50, 75 and 100% of the commercial height of the trees. The chemical analysis had as reference the ABTCP (1974) norms and the physical tests, the ABNT/NBR 11941-02 (2003) norms. In the quantification of extractives, cold water presented the lowest average (3.91%) and sodium hydroxide the largest (20.57%). The average lignin content was 30.29% and the average specific mass was 0.530 g cm-³. Data were analyzed based on analysis of variance, means test and principal components (PCA). It was concluded that the woodstudied presented technological characteristics compatible to be used in the furniture area, as well as in external constructions, showing competitive potential to operate in the sector.Keywords: extractives; lignin; basic specific mass; quality wood.
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