O objetivo deste estudo foi estimar os parâmetros genéticos quantitativos das progênies sob o efeito de geada, bem como determinar a interação genótipos x ambientes das progênies de Eucalyptus dunnii em dois locais de estudo. Os testes de progênies foram implantados em 2010, utilizando 20 progênies de polinização aberta de E. dunnii. Foram avaliados: altura de planta (ALT), diâmetro à altura do peito (DAP) e volume de madeira em metros cúbicos (VOL). Foram realizadas as análises estatísticas e descritivas, correlação fenotípica/genotípica por local e análise de variância conjunta, sendo estimados os parâmetros genéticos. Foram detectadas diferenças significativas (p≤0,05) entre progênies para as características silviculturais, o que sugere a possibilidade de melhoramento pela seleção. Pela análise conjunta, a interação progênies x ambientes (G x E) não apresentou diferença significativa, confirmando que as progênies superiores identificadas nos testes podem ser indicadas para ambos os locais. Os resultados de correlações genéticas e fenotípicas variaram de baixos a altos (0,23 a 1,0) para as características estudadas, sendo as correlações, em sua grande maioria, significativas (p≤0,05), em que o DAP foi altamente correlacionado com o VOL. A população, por apresentar alta variação genética e controle genético das características, permite a obtenção de ganhos com a seleção entre as progênies.

This study investigated the genetic variability in progenies of Eucalyptus dunnii Maiden for resistance against rust (Puccinia psidii). Field experiments were installed in two regions with differentsoil-climatic conditions. Open-pollinated progenies were established in arandomized complete block design. Sixty and 48 progenies were evaluated underfield conditions at two sites, respectively, with six replications and eight trees per plot. In another experiment in a controlled environment, 53 progenies were evaluated in randomized blocks with six replications and nine plants perplot. The following traits were evaluated: plant height, severity of pestattack and the most susceptible stage to the leaf disease. The genetic variability for rust resistance in the E. dunnii population under studywas high, with a genetic coefficient of variation of 36.07%; 7% of thee valuated progenies were rust-resistant. It indicates a high potential for selection and breeding of the species.

The galling insect Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) is a major limiting factor in the cultivation of drought-tolerant eucalyptus. The insect L. invasa is a major pest of eucalyptus plantations, and Beauveria bassiana (Bals.) Vuill (Ascomycota: Hypocreales) is being investigated as a potential biocontrol agent against this pest. The fungus B. bassiana can produce metabolites that affect insect biology and survival. Here, we investigated the ability of the entomopathogenic B. bassiana to endophytically develop and induce resistance to L. invasa in a drought-tolerant eucalyptus hybrid. In a greenhouse under semi-controlled conditions, a group of seedlings were sprayed with a solution containing the fungal spores of B. bassiana. The uninoculated seedlings and seedlings inoculated were infested with L. invasa, and their morphometric responses, gas exchange, and chlorophyll indexes were assessed. The number of leaves and height of the inoculated plants was higher than those of the uninoculated plants. The mean CO₂ assimilation rate (A) and transpiration rate (E) were higher for inoculated plants. The inoculated plants showed higher chl a and chl b contents. Compared to the uninoculated plants, the inoculated plants developed much fewer galls, while some showed only scar formations where L. invasa deposited its eggs. These results indicated that inoculating Eucalyptus with B. bassiana promoted resistance to L. invasa. To the best of our knowledge, this is the first study showing that an entomopathogenic fungus can develop endophytically to promote resistance against a galling insect pest.

Cassava (Manihot esculenta Crantz) is a staple crop widely cultivated by small farmers in tropical countries. However, despite the low level of technology required for its management, it can be affected by several diseases, with anthracnose as the main threat. There is little information about the main species of Colletotrichum that infect cassava in Brazil. Thus, the objective of this work was to study the diversity, prevalence and virulence of Colletotrichum species that cause anthracnose in cassava leaves in northern Brazil. Twenty municipalities of the Pará and Tocantins states were selected, and leaves with symptoms were collected in those locations. Pure cultures were isolated in the laboratory. Species were identified using phylogenetic analyses of multiple loci, and their pathogenicity, aggressivity and virulence levels were assessed. Our results showed the greatest diversity of Colletotrichum associated with anthracnose in cassava plants of the “Formosa” cultivar in the Tocantins and Pará states. We determined the presence of Colletotrichum chrysophilum, C. truncatum, C. siamense, C. fructicola, C. plurivorum, C. musicola and C. karsti, with C. chrysophilum as the most aggressive and virulent. Our findings provide accurate identifications of species of Colletotrichum causing anthracnose in cassava crops, which are of great relevance for cassava breeding programs (e.g., the search for genotypes with polygenic resistance since the pathogen is so diverse) and for developing anthracnose management strategies that can work efficiently against species complexes of Colletotrichum.

The seed physiological maturity knowledgment is critical determine its maximum production and physiological quality. The objective of this study was to determine the ideal time to harvest by evaluating seeds physiological maturity. Seventeen weekly harvests of fruits and seeds from matrices located in the Brazilian city of Botucatu, SP, were performed from May to September 2001. Fruits size and weight, seed water content and dry matter, and germination and emission of primary root were evaluated. Seeds showed maximum dimension in the thirteenth week of collection, while the highest fruit weight was obtained in the twelfth week of collection. Water content decreased over time. Seeds dry matter showed its highest value in the sixteenth week harvest, while germination percentage showed its highest value between the fourteenth and fifteenth week harvest. The percentage of primary root emission was observed with maximum value in the tenth week harvest. Based on the results, it is concluded that the best Anadenanthera colubrina harvest season occurs between the fourteenth and fifteenth weeks.