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Thyrinteina arnobia (Lepidoptera: Geometridae) is a native American species. Despite its historical importance as an insect pest in Eucalyptus plantations, more information is needed regarding the population diversity, demography, and climatic variables associated with its distribution in different regions of Brazil. We used a phylogeographic approach to infer the genetic diversity, genetic structure, and demographic parameters of T. arnobia . We also conducted an ecological niche modeling (ENM) to predict suitable areas for T. arnobia occurrence in Brazil and other countries worldwide. Although T. arnobia populations have low genetic diversity in Brazil, we identified mitochondrial haplogroups predominating in different Brazilian regions and high Ф ST and Ф CT values in AMOVA, suggesting a low frequency of insect movement among these regions. These results indicate that outbreaks of T. arnobia in Eucalyptus areas in different regions of Brazil are associated with local or regional populations, with no significant contribution from long-distance dispersal from different regions or biomes, suggesting that pest management strategies would be implemented on a regional scale. In Brazil, the demographic and spatial expansion signals of T. arnobia seem to be associated with the history of geographical expansion of Eucalyptus plantations, a new sustainable host for this species. ENM indicated that isothermality and annual rainfall are critical climatic factors for the occurrence of T. arnobia in tropical and subtropical areas in the Americas. ENM also suggested that T. arnobia is a potential pest in Eucalyptus areas in all Brazilian territory and in regions from Africa, Asia, and Oceania.

Rust caused by Puccinia psidii is one the most destructive diseases of Eucalyptus . Management of the disease is achieved through selection of resistant host genotypes. Recently, eucalypt plants from clone BA6021, resistant to P. psidii isolate race-1, were infected by rust in Brazil. Microsatellite profiles of infected plants confirmed that the host was indeed clone BA6021. In pathogenicity tests, the resistant clones BA6021 and G21 (which carry the resistance gene Ppr-1 ) were found susceptible to the newly discovered isolate EUBA-1, indicating a new biotype of the pathogen. These results show that the isolate EUBA-1 and other potentially unrecognized pathogen races should be given strong consideration for eucalypt breeding programs aimed rust resistance.

Seeds from different species and provenances of Myrtaceae, collected from wild populations in Australia, were screened for resistance to rust caused by Puccini psidii . Seedlings were inoculated with a suspension of rust inoculum and incubated in a mist chamber in the dark for 24 h. Subsequently, the plants were transferred to a growth chamber and rust reaction was evaluated 12 days later. Inter- and intra-specific variability was observed among and within the myrtaceae species. Independent of the provenance, the most resistant species were: Corymbia calophylla ‘ rosea ’, C. tesselaris , Melaleuca ericifolia , Eucalyptus tereticornis , E. resinifera , E. scias subsp. scias , E. paniculata , E. pellita and C. intermediata . In contrast, M. nesophila , M. alternifolia , M. cajuputi subsp. cajuputi , M. leucadendra , M. quinquenervia , E. cloeziana , E. diversicolor , E. regnans and E. grandis displayed the highest number of susceptible plants. Among those additional myrtaceaceous genera which were tested for their reaction to rust the most resistant were Asteromyrtus dulcia , A. tenuifolia , Gossia fragrantissima , Lophostemon confertus , Syzygium australe , S. wilsonii subsp. cryptophlebium , Archirhodomytus beckleri , Acmena smithii and Syzygium alatoramulum. Pericalymma ellipticum , Kunzea baxteri , Astartea heteranthera , Regelia ciliata , Rhodomyrtus psidioides and Syncarpia glomulifera were the most susceptible species.

Rust, caused by Puccinia psidii , is an important disease in eucalyptus nurseries and plantations in Brazil. In the field, eucalyptus plants taller than 3–4 m are not infected by the pathogen. We hypothesised that microclimatic conditions above 3 m do not favour either pathogen establishment or disease development. Therefore, we evaluated the effect of the height gradient on rust incidence, related to leaf wetness duration and the number of airborne urediniospores. Young eucalyptus plants were maintained at heights from 0.5 to 4.0 m, and disease was assessed weekly at all heights in five plant sets. Rust incidence reduced as height increased. The values of area under rust progress and rust incidence were negatively correlated ( P ≤ 0.05) with height and positively correlated ( P ≤ 0.05) with the number of both hours with leaf wetness and airborne urediniospores. Thus establishment and progress of eucalyptus rust were affected by leaf wetness duration and concentration of airborne urediniospores, which decreased as the height increased.

Abstract Eucalyptus plantations are expanding in Brazil to meet growing demands for wood-based products, such as pulp, paper, and bioenergy. New clones and silvicultural adjustments are needed with the advance of eucalypts to new regions within Brazil. This study’s objective was to evaluate the effect of variable spacing on the development of six Eucalyptus clones cultivated in the Cerrado region of Brazil. These clones were evaluated in a systematic design, with 23 spacing treatments and five biological replicates. Spacing per tree ranged from 1.20 m2 to 21 m2. At two, four, and six years after planting, diameter at breast height (DBH) and height of all trees were measured to estimate wood volume. Regression models were fitted for each trait (DBH, height, and wood volume) and showed that DBH growth was positively affected by spacing, especially at four and six years after planting (R2 > 0.58). Consequently, estimates of individual volume per tree also had a positive relationship with spacing. Total stand volume, on the other hand, was higher under densest spacings. The GG100 clone outperformed all other clones, with higher stand wood volume, especially under the densest spacings. The CCL55 clone is a promising genotype, especially under dense plantations.

The identification of genotypes more tolerant to water deficit is a challenge to breeding programs. In this research, our objectives were to identify and validate traits for tolerance to water deficit in eucalypts. The estimation of genotypic parameters and early selection are proposed based on mixed models, selection indexes and validation schemes. Seedlings with 110 days were grown in a greenhouse for 12 weeks, and two water deficit treatments were conducted (polyethylene glycol and water limitation). A total of 26 biomarkers were evaluated, and 15 of them were significant, exhibited adequate heritability, and used for screening: final plant height, increment in height, increment in diameter, area of mature and fully expanded leaf, nutrient contents of N, K, Ca, Mg, S, Cu, Zn, Mn and B, photosynthesis (A) and stomatal conductance (gs). Both treatments were adequate to discriminate water deficit-tolerant clones. The ranking of tolerant clones according to their phenotype in the field demonstrates the potential for early selection and is consistent with the maintenance of water-deficit-tolerance mechanisms until adulthood. There is evidence that the choice of biomarker depends on the species involved and different strategies contributing to the tolerance trait.

The identification of genotypes more tolerant to water deficit is a challenge to breeding programs. In this research, our objectives were to identify and validate traits for tolerance to water deficit in eucalypts. The estimation of genotypic parameters and early selection are proposed based on mixed models, selection indexes and validation schemes. Seedlings with 110 days were grown in a greenhouse for 12 weeks, and two water deficit treatments were conducted (polyethylene glycol and water limitation). A total of 26 biomarkers were evaluated, and 15 of them were significant, exhibited adequate heritability, and used for screening: final plant height, increment in height, increment in diameter, area of mature and fully expanded leaf, nutrient contents of N, K, Ca, Mg, S, Cu, Zn, Mn and B, photosynthesis (A) and stomatal conductance (gs). Both treatments were adequate to discriminate water deficit-tolerant clones. The ranking of tolerant clones according to their phenotype in the field demonstrates the potential for early selection and is consistent with the maintenance of water-deficit-tolerance mechanisms until adulthood. There is evidence that the choice of biomarker depends on the species involved and different strategies contributing to the tolerance trait.