ABSTRACT Drought is likely the main abiotic stress that affects wheat yield. The identification of drought-tolerant genotypes represents an effective way of dealing with the continuous decrease in water resources as well as the increase in world population. The aim of this study was to identify single nucleotide polymorphisms (SNP) associated with drought tolerance indices in wheat by using a genome-wide association study (GWAS) under fully irrigated and rain-fed conditions. The drought tolerance indices (i.e., Stress Susceptibility Index, Stress Tolerance Index, Tolerance Index and Yield Stability Index) were calculated based on grain yield, 1,000-kernel weight and kernels per spike. The association panel was genotyped using genotyping-by-sequencing (GBS). A total of 175 SNPs exhibited statistical evidence of association with at least one drought tolerance index, explaining up to 6 % of the phenotypic variation. Forty-five SNPs were associated with more than one tolerance index (up to 4 agronomic traits). Most associations were located on chromosome 4A, supporting the hypothesis that this chromosome has a key role in drought tolerance which should be exploited for wheat improvement. In addition, statistical analysis detected SNPs associated with tolerance indices in both growing seasons, providing information about genetic regions with stable effects under different environmental conditions. This GWAS experiment serves as one of the few studies on association mapping for drought tolerance indices in wheat, which could increase the efficiency of rain-fed and irrigated crop production.

ABSTRACT Eucalyptus globulus is one of the most commonly planted hardwood species for industrial use in various temperate regions around the world. The present study aimed to evaluate 62 full-sib families of E. globulus in one of the southernmost progeny trials of the species in the south of Chile. Estimates of genetic parameters for stem straightness, branching quality and growth traits were based on a Bayesian modelling approach using Gibbs sampling. A Bayes Factor (BF) analysis supported the hypothesis of significant additive genetic variation for all traits under study. Conversely, the BF supported a model with significant dominance effects for the diameter at breast height and stem volume, which explained up to 25% of the phenotypic variation. The greatest narrow-sense heritability estimates were found for the tree height and stem straightness, which were 0.15 (0.08 to 0.26) and 0.18 (0.10 to 0.28), respectively (mean of posterior distributions and 90% credible sets). In turn, the branching quality had a low heritability (narrow-sense) that varied from 0.05 to 0.10 (90% Bayesian credible region). The mean posterior estimate of genetic correlation between both quality traits was 0.22 (0.01 to 0.63, 90% credible set from a bi-trait threshold model), which indicates that stem straightness is positively related to branching quality. Our findings reveal that the study population responds to common patterns of breeding populations of E. globulus. This information is valuable for the development of improved seeds in the southern zone of Chile.

ABSTRACT The development of commercial maize hybrids tolerant to herbicide and resistant to lepidopterans has allowed an important ex pansion of this crop in Brazil. The objective of this study was to field-evaluate the performance of eleven maize hybrids at three different growing locations in Brazil to find adapted and stable hybrids. The fields were desiccated using glyphosate (3 L ha-1) seven days before seeding. Each trial was arranged in a randomized complete block design with four replications per location. In the joint analysis of eight agronomic traits, the error variances were considered heterogeneous among locations. The eleven hybrids presented significant differences in all traits. The hybrid DKB340PRO2 had the highest grain yield, which could be a recommended hybrid to local farmers. In addition, the hybrid x location interaction was not statistically significant (p > 0.05), indicating stability of all the studied hybrids. Significant differences existed among the corn hybrids for eight agronomic traits, supporting our research hypothesis.

RESUMEN El desarrollo de híbridos comerciales de maíz tolerantes a herbicidas y resistentes a plagas ha permitido una importante expansión de este cultivo en Brasil. El objetivo de este estudio fue evaluar el desempeño de 11 híbridos comerciales de maíz en condiciones de campo, cultivados en tres localidades de Brasil, con el fin de identificar los híbridos mejor adaptados y estables. Los ensayos de campo fueron tratados con glifosato (3 L ha-1) siete días antes de la siembra. Cada ensayo se estableció de acuerdo a un diseño de bloques completamente aleatorizados, con cuatro repeticiones por tratamiento. La evaluación agronómica de los 11 híbridos consideró ocho características de importancia agrícola. De acuerdo a los resultados, hubo diferencia significativa entre tratamientos para todas las características estudiadas. Particularmente, el híbrido DKB340PRO2 obtuvo el mayor rendimiento de granos, por lo tanto, podría ser un híbrido recomendado para los productores locales. La interacción híbrido x sitio no fue significativa, lo cual implica que todos los híbridos estudiados tuvieron un desempeño estable.

The development of micropropagation techniques in orchid has many advantages such as the reproduction of elite, rare, sterile and/or disease-free genotypes. The aim of this study was to evaluate the use of organic supplements (coconut water and banana pulp) in the in vitro development of seedlings of Laeliocattleya (Hadrolaelia purpurata x Cattleya intermedia), comparing their response to plant growth regulators: auxins and cytokinins. For this, the following four experiments were carried out: 1. Organic supplements compared to different concentrations ofkinetin (N6-furfuryl aminopurine; KIN) and naphthaleneacetic acid (NAA), 2. Organic supplements compared to different concentrations of 3-indolebutyric acid (IBA) and N6-benzyladenine (6BA), 3. Organic supplements compared to different concentrations of IBA and KIN, and 4. Organic supplements compared with different concentrations ofANA and 6BA. Coconut water was statistically superior to the others (P <0.01) for the variable number of leaves, in all experiments performed with 7.3 leaves per seedling cultivated in vitro. While banana pulp showed the best results in the number of roots (P <0.01) for all experiments, with an average value of 7.4 roots. The addition of banana pulp and/or coconut water is suitable for the production of orchid hybrids, which present a positive effect on the development of seedlings. Its low cost is also a plus in relation to the use ofplant growth regulators.

El desarrollo de técnicas de micropropagación en orquídeas ofrece múltiples ventajas como la reproducción de genotipos superiores, raros, estériles o libres de enfermedades. El objetivo del presente trabajo fue evaluar el uso de suplementos orgánicos (agua de coco y pulpa de banana) en el crecimiento y desarrollo in vitro de plántulas del híbrido intergenérico Laeliocattleya (Hadrolaelia purpurata x Cattleya intermedia), comparando su respuesta con fitorreguladores de auxinas y citoquininas. Para ello se realizaron los siguientes cuatro experimentos: 1. Suplementos orgánicos comparados con diferentes concentraciones de kinetina (N6-furfuril amino purina; KIN) y ácido naftalenacético (ANA), 2. Suplementos orgánicos comparados con diferentes concentraciones de ácido 3-indolbutírico (IBA) y N6-benzyladenine (6BA), 3. Suplementos orgánicos comparados con diferentes concentraciones de IBA y KIN, y 4. Suplementos orgánicos comparados con diferentes concentraciones de ANA y 6BA. El suplemento orgánico de agua de coco fue estadísticamente superior al resto (P<0,01), para la variable número de hojas, en todos los experimentos realizados, con 7,3 hojas por plántula cultivada in vitro. En tanto que la adición de pulpa de banana mostró los mejores resultados en el número de raíces (P<0,01), para todos los experimentos en estudio, con un valor medio de 7,4 raíces. Se concluye que la adición de pulpa de banana o de agua de coco es conveniente para la producción de orquídeas híbridas por presentar un efecto positivo en el desarrollo de las plántulas, y por su costo reducido en relación con el uso de reguladores de crecimiento.

Eucalyptus cladocalyx F. Muell é distribuída em quatro regiões isoladas do sul da Austrália: Kangaroo Island, Flinders Ranges e em duas zonas da Eyre Peninsula. A espécie tem a capacidade de crescer em condições ambientais extremas como ambientes secos e solos salinos. O objetivo do presente estudo foi examinar a diversidade genética em 45 famílias de meio-irmãos cultivadas no norte do Chile, as quais são originarias de cinco localidades diferentes (procedências). A variabilidade genética foi avaliada usando marcadores moleculares ISSR (Inter Simple Sequence Repeat). Os resultados mostraram baixo nível de diversidade genética dentro de populações (He = 0,113 a 0,268) em contraste com outras espécies de Eucalyptus. Adicionalmente, houve uma significativa diferenciação genética entre procedências (Φst = 0.14), coincidindo com a reportada em estudos anteriores. Kangaroo Island é a procedência mais diferenciada. O presente estudo evidenciou que os recursos existentes no Chile são uma amostra representativa das populações Australianas e, portanto, o germoplasma cultivado no norte do Chile seria suficiente para os programas de melhoramento. A tecnologia de marcadores ISSR poderia ser uma alternativa para identificar genótipos de interesse no processo de seleção.

Eucalyptus cladocalyx F. Muell is a tree endemic to southern Australia and is distributed across four isolated regions: Kangaroo Island, southern Flinders Ranges, and two geographical zones in Eyre Peninsula. E. cladocalyx is capable of growing under extreme environmental conditions, including dry and saline soils. The objective of this study was to analyze genetic diversity in 45 half-sib families planted in northern Chile that are distributed across five different zones (provenances). Genetic variability was assessed using ISSR (Inter Simple Sequence Repeat) molecular markers. The results showed low levels of genetic diversity within populations (He = 0.113 to 0.268) in contrast with other Eucalyptus species. In addition, there was a significant genetic differentiation among provenances (Φst = 0.14); populations from the Kangaroo Island provenance showed more differentiation than any other population. These results are in agreement with previous studies of the species. Our study revealed that Chilean resources are a representative sample of Australian populations; therefore, the germplasm planted in northern Chile would be sufficient for the development of improvement programs. ISSR-Marker technology could be an alternative to identify genotypes of interest in material selection.