Background and Objectives. Water stress is a major constraining factor of Eucalyptus plantations’ growth. Within a genetic improvement program, the selection of genotypes that improve drought resistance would help to improve productivity and to expand plantations. Leaf characteristics, among others, are important factors to consider when evaluating drought resistance evaluation, as well as the clone’s ability to modify leaf properties (e.g., stomatal density (d) and size, relative water content at the time of stomatal closure (RWCc), cuticular transpiration (Ec), specific leaf area (SLA)) according to growing conditions. Therefore, this study aimed at analyzing these properties in nursery plants of nine high-productivity Eucalyptus clones. Material and Methods: Five Eucalyptus globulus Labill. clones and four hybrids clones (Eucalyptus urophylla S.T. Blake × Eucalyptus grandis W. Hill ex Maiden, 12€; Eucalyptus urograndis × E. globulus, HE; Eucalyptus dunnii Maiden–E. grandis × E. globulus, HG; Eucalyptus saligna Sm. × Eucalyptus maidenii F. Muell., HI) were studied. Several parameters relating to the aforementioned leaf traits were evaluated for 2.5 years. Results: Significant differences in stomatal d and size, RWCc, Ec, and SLA among clones (p < 0.001) and according to the dates (p < 0.001) were obtained. Each clone varied seasonally the characteristics of its new developing leaves to acclimatize to the growth conditions. The pore opening surface potential (i.e., the stomatal d × size) did not affect transpiration rates with full open stomata, so the water transpired under these conditions might depend on other leaf factors. The clones HE, HG, and 12€ were the ones that differed the most from the drought resistant E. globulus control clone (C14). Those three clones showed lower leaf epidermis impermeability (HE, HG, 12€), higher SLA (12€, HG), and lower stomatal control under moderate water stress (HE, HG) not being, therefore, good candidates to be selected for drought resistance, at least for these measured traits. Conclusions: These parameters can be incorporated into genetic selection and breeding programs, especially Ec, SLA, RWCc, and stomatal control under moderate water stress.

ResumoO presente trabalho teve como objetivo estudar a variabilidade genética e as alterações das características morfológicas em progênies de polinização aberta de Eucalyptus grandis sob o efeito do biorregulador de crescimento paclobutrazol. O experimento foi instalado no delineamento em blocos casualizados. As modificações que ocorreram antes e durante a indução floral das plantas foram estudadas e os parâmetros genéticos estimados para altura de plantas e diâmetro do caule. O regulador paclobutrazol causou modificações morfológicas durante o desenvolvimento das plantas; que foram intensas logo após a aplicação do regulador e foram diminuindo seu efeito ao longo das avaliações. Os coeficientes de variação mostraram haver maior variabilidade genética dentro do que entre progênies, para as características estudadas, apontando para maior eficiência na seleção dentro das progênies em programas de melhoramento do Eucalyptus grandis.Palavras-chave adicionais: eucalipto; parâmetros genéticos; regulador vegetal. AbstractThe research objective was to study the genetic diversity of morphological traits in Eucalyptus grandis progenies growing under paclobutrazol regulator effects. The progeny trail was set up through design of randomized blocks. The morphological changes occurred before and during the plant flowering were analyzed. The estimation of genetic parameters were for plant height and stem diameter. The paclobutrazol have caused changes on plant development being strong by the beginning and becoming lightening through the evaluations. The coefficients of variation have shown there is higher genetic diversity within than among progenies for the studied traits. Therefore, it can have high efficiency on selection within progenies in the Eucalyptus grandis breeding program.

This study assessed the genetic variability in open-pollinated progenies of Eucalyptus urophylla for resistance to rust (Puccinia psidii). The progeny trial was conducted on a statistical randomized block design with 20 progenies, five plants per plot, and nine replications. Analysis of variance showed high genetic variability for the studied trait, with potential for selection gains. The genetic variability of this population provides support to conduct a breeding program with superior individuals for rust resistance, allowing low costs and minimizing the yield losses on eucalyptus plantations.

ResumoO guapuruvu é uma espécie pioneira de rápido crescimento da família Leguminosae de grande importância em projetos de restauração. O objetivo do estudo foi verificar a variabilidade genética de progênies de Schizolobium parahyba da região de Botucatu/SP, por meio de parâmetros genéticos quantitativos. O teste de progênies foi instalado no delineamento experimental em blocos casualizados, três repetições, quatro plantas por parcelas e 60 progênies. Foram avaliados os caracteres: altura de plantas (ALT) e diâmetro á altura do peito (DAP) nas idades de 2, 7, 14, 20 e 66 meses e a porcentagem de sobrevivência, aos 66 meses, transformada em log (x+10). Para as estimativas dos parâmetros genéticos, os dados coletados foram analisados pelo software SELEGEN. Os coeficientes de variação genética individual (CV gi %), variação genotípica entre progênies (CV gp %) e variação relativa (CV r ), apresentaram estimativas que demonstram uma variabilidade genética restrita e muito influenciada pelo ambiente. Os coeficientes de herdabilidade ao nível individual (ĥ a 2 ) foram maiores para altura (0,318, 0,012, 0,247, 0,390 e 0,012) em relação ao DAP (0,021, 0,024 e 0,015) aos 14, 20 e 66 meses, respectivamente. As correlações genotípicas no geral foram altas entre os caracteres ALT e DAP. A maior correlação genética entre os caracteres DAP e ALT de plantas ocorreu entre a idade 14 meses (0,85). As progênies estudadas, apesar de não mostrarem significativa variabilidade genética, são potenciais para se dar início a programas de melhoramento e conservação genética.Palavras chave: Guapuruvu, melhoramento florestal, parâmetros genéticos, teste de progênies, variabilidade genética. AbstractThe guapuruvu is pioneer specie by fast growing of legume family with great importance in restoration projects. The aim of the study was to assess the genetic variability of offspring of Schizolobium parahyba through quantitative genetic parameters. The progeny test was installed in a randomized block design in three replications four plants per plot with 60 progenies. Was evaluated plant height, diameter at breast height with the ages: 2, 7, 14, 20 and 66 months and the percentage of survival at 66 months. For the estimates of genetic parameters, the data were analyzed by software SELEGEN. The heritability coefficients at individual level (ĥ a 2 ) were higher by height (0.318, 0.012, 0.247, 0.390 and 0.012) compared to DBH (0.021, 0.024 and 0.015) in the 14, 20 and 66 months, respectively. The highest genetic correlation between characters and plant height DBH occurred in the period of 14 months (0.85). The progenies studied, despite not show significant genetic variability, have the potential to initiate programs of forest breeding and for conservation genetics.

ResumoA pesquisa teve como objetivo estudar o controle genético de caracteres silviculturais em progênies de Eucalyptus urophylla para a tolerância à geada. Foram instalados três testes de progênies de polinização aberta em blocos casualizados, 150 progênies, quatro repetições, seis plantas/parcela. Os testes foram implantados em duas regiões contrastantes para a ocorrência de geadas. Em áreas de geadas os testes foram implantados nas áreas das empresas Eucatex (Itatinga/SP) e Palmasola (Palma Sola/SC), e na Estação Experimental de Anhembi/SP, onde a ocorrência de geadas é rara. Altura de plantas, diâmetro à altura do peito e volume de madeira, aos 12 e 24 meses de idade foram mensuradas. A variabilidade gené-tica na população foi alta, o coeficiente de variação genético individual variou de 5,85% (ALT) até 22,58% (VOL) e a herdabilidade no sentido restrito de 0,13 (ALT) até 0,77 (DAP e VOL), indicando um elevado potencial para seleção e melhoramento da espécie para a tolerância ao frio.Palavras-chave: parâmetros genéticos; melhoramento florestal; geada. AbstractThis research aimed to study the genetic control of silvicultural traits in Eucalyptus urophylla progenies for frost tolerance. Three open-pollinated progeny tests were installed in a randomized blocks design, 150 progenies, four replications, six plants per plot. The tests were implemented in two contrasting regions for the occurrence of frost. In areas with frost occurrence the tests were implemented in the Eucatex (Itatinga/ SP) and Palmasola (Palma Sola/SC) companies; for areas with rare frosts the trial was established in Experimental Station of Anhembi/SP. Plant height; diameter at breast height and wood volume at 12 and 24 months old were measured. The genetic variability in the population was high, the individual genetic variation coefficient ranging from 5.85% (ALT) to 22.58% (VOL) and the heritability in the narrow sense from 0.13 (ALT) to 0.77 (DAP and VOL), indicating a high potential for selection and breeding of the species for frost tolerance.