Aplicación de índices de tolerancia a la salinidad en plántulas de maíz

Los objetivos de este trabajo fueron: estudiar la aplicación de diferentes índices de tolerancia en caracteres de plántulas de maíz y evaluar su posible utilidad en la identificación de genotipos tolerantes a la salinidad. Se probaron 68 accesiones en dos ambientes (0 y 100m MClNa). Se midieron: largo de raíz, vástago y 3ª hoja y peso seco de raíz y de parte aérea. Se incluyeron 6 índices de tolerancia: índice de susceptibilidad al estrés (SSI), índice de tolerancia al estrés (STI), tolerancia al estrés (TOL), media geométrica de la productividad (GMP), productividad media (MP) e índice de estabilidad del rendimiento (YSI). Debido a la variación espacial relacionada con la concentración de sal en ambientes salinos, sería importante identificar genotipos estables frente a una gama amplia de suelos salinos. El biplot agrupó las accesiones, caracteres medidos en ambientes con y sin estrés e índices de tolerancia a sal, y demostró que los índices GMP, MP y STI fueron los que permitieron identificar los accesiones estables que se caracterizan por tener una alta expresión de estos caracteres en ambos ambientes. La aplicación del método de Componentes Principales (CP) identificó a los caracteres peso seco aéreo y largo de raíz como los de mayor contribución y ambos estuvieron asociados con dichos indices de tolerancia a salinidad. De esta manera, en este estudio las accesiones 1, 7, 30, 33, 43 y 45 fueron los más estables para los caracteres peso seco aéreo y largo de raíz. Entre ellos las accesiones 30 y 33 fueron superiores (pertenecientes a genotipos del Grupo A) porque mostraron los escores más altos sobre el eje CP1 pero sus aportes al CP2 fueron bastantes pequeños, para la mayoría de las variables.The aims of this research were: to study the application of different tolerance Indices in traits measured in maize seedlings and to assess their possible use in the identification of genotypes tolerant to salinity. Sixty eight accessions were tested in two environments (0 and 100mM NaCl). We recorded length for radicle, shoot and third leaf and dry weight for root and shoot. Six stress tolerance indices were included: stress susceptibility (SSI), stress tolerance index (STI), stress tolerance (TOL), geometric mean productivity (GMP), mean productivity (MP) and yield stability index (YSI. Saline environments show a great spatial variation in relation to the salt concentration, for this reason it would be important to identify genotypes with stable behavior in a variety of saline soils. The biplot method allowed clustering accessions, traits measured in stress and non stress environment and salt tolerance Indexes in a same graphic, and showed that GMP, MP and STI indexes were the ones who helped identify the high yielding (group A genotype) and stable accessions, characterized by a high expression of these characters in both environments. Principal Component method showed that shoot dry weight and root length had the highest contribution and both were associated with these above indices in salinity. Therefore, in this study the accessions: 1, 7, 30, 33, 43 and 45 had stable values for the traits root length and shoot dry weight. Within this group the 30 and 33 entries were superior (bellowing to Group A genotypes) because they had the highest PC1 scores but its PC2 scores were rather small for the most of the variables.Fil: Collado, Mónica B.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto Fitotécnico de "Santa Catalina"; ArgentinaFil: Aulicino, Mónica Beatriz. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto Fitotécnico de "Santa Catalina"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Arturi, Miguel Jacinto. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto Fitotécnico de "Santa Catalina"; ArgentinaFil: Molina, María del Carmen. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto Fitotécnico de "Santa Catalina"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Generational Mean Analysis of Salt Tolerance during Osmotic Phase in Maize Seedling

This study details the nature and magnitude of the genetic effects associated with various quantitative characters (morphological and hydric relations) measured in maize seedlings during the osmotic phase of saline stress (100 mM NaCl). Three lines with differential behavior in salt stress: SC2 (tolerant), AFE (susceptible) and LP3 (moderately tolerant) were used to obtain contrasting crosses (SC2 × AFE) and (SC2 × LP3). An analysis of six generational means (P 1, P 2, F 1, F 2, BC1 and B C 2) was applied for each cross. First a scaling test was applied and then a three and six-parameter genetic models were used to estimate various genetic components. In none of the traits studied there was evidence of adequacy to the three parameter model, which indicates important epistatic effects in genetic expression. The dominant genetic effects were greater than the additive ones for all the characters evaluated. LG showed positive and significant differences for [h] in both crosses, indicating the presence of hybrid vigor and its possible use in the improvement. Low value of [d] and high of [h] both significant in SC2 × AFE, indicates existence of genes dispersion between the parental lines. While, for the cross SC2 × LP3, the low and significant value of [d] and not significant value of [h], indicate greater genetic similarity. In the SC2 × LP3 cross, the negative interaction [l ] confirms ambidirectional dominance, while for SC2 × LP3 the positive sign indicates directional dominance. The analysis of tolerance to salinity in the osmotic phase showed a complex polygenic inheritance for the traits used, determined by simple and interaction effects of different magnitudes and significance according to the cross considered.Facultad de Ciencias Agrarias y Forestales (FCAF

Selection of Maize Genotypes with Tolerance to Osmotic Stress Associated with Salinity

Thirteen different inbred lines in relation to the type of grain and life cycles were characterized by testing for osmotic stress associated with salinity. The identification of tolerant genotypes would be an effective strategy to overcome the saline stress. Osmotic stress reduces immediately the expansion of the roots and young leaves which determine a reduction in the size of the plant. A completely randomized design was adopted to test seedlings under controlled conditions of light and temperature. Two treatments were used: 0 mM NaCl (as control) and 100 mM NaCl. After 15 days of complete salinization, the seedlings were harvested and several morphological traits were measured.The morphological traits of growth were leaf growth (Ar1, Ar2, Ar3 and Ar4), dry masses of shoot and root (SDM and RDM, respectively). Also, traits associated with water economy were registered: leaf water loss (LWL) and relative water content (RWC). The morphological traits were expressed in relative terms, while the traits associated with the economy of water were expressed in absolute terms. Uni and multivariate techniques were applied to identify genotypes with divergent behaviors to osmotic stress tolerance. Also, a Tolerance Index was employed to identify superior genotypes. Four clusters were obtained after applying a Cluster Analysis and PrincipalComponent Analysis (PCA). The genotypes were compared to each other with a test of DMS. The results obtained with different statistical techniques converged. Some variables presented a differential weight classification of genotypes. The morphological traits like RDM, SDM, Ar3, Ar4 and Ar5 were the most discriminating. Tolerance Index allowed to classify genotypes, thus SC2 andAD3 lines were that reached highest value of the index and therefore would be tolerant lines,while AF3 and LP3 had a low index and were seen as sensible.Fil: Collado, Mónica B.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto Fitotécnico de "Santa Catalina"; ArgentinaFil: Aulicino, Mónica Beatriz. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto Fitotécnico de "Santa Catalina"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Arturi, Miguel Jacinto. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto Fitotécnico de "Santa Catalina"; ArgentinaFil: Molina, María del Carmen. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto Fitotécnico de "Santa Catalina"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

Modelo de variación regional en germoplasma de Bromus catharticus (Poaceae) en Argentina asociado con las condiciones ambientales

Thirty-one populations of Bromus catharticus Vahl., collected from the Pampean Dominion (Argentina), were classified using twenty four highly heritable traits by numerical taxonomic methods. After implementing a stepwise discriminant analysis, 18 traits were chosen as classificatory variables. Eight population groups were classified in two main clusters. Different morphotypes, primarily associated with panicle architecture and micro floral traits, were found. The patterns in the morphological variation seem to correspond to a gradient of humidity and temperature that diminishes from the NE to the SW. This pattern of classification reflects the geographical origin for most of the sampled populations, although there was some noise. Our results fit the patchy variation model, where populations are genetically selected for macro and micro environmental conditions.Treinta y una poblaciones de Bromus catharticus Vahl., recolectadas en el dominio Pampeano (Argentina), fueron clasificadas utilizando 24 caracteres altamente heredables por métodos de taxonomía numérica. Tras implementar el análisis discriminante del paso a paso (Stepwise), 18 variables fueron seleccionadas como variables clasificatorias. Ocho grupos de poblaciones fueron clasificadas en dos clusters principales. Diferentes morfotipos, principalmente asociados a la arquitectura de las panojas y a variables microflorales, fueron encontrados. El patrón de variación morfológico parece responder a un gradiente de humedad y temperatura que disminuye desde el NE al SW. Además, dicho patrón de clasificación refleja un origen geográfico para la mayoría de las poblaciones, aunque hubo algo de ruido. Nuestros resultados se ajustan a un modelo de variación en parches, donde las poblaciones están genéticamente seleccionadas por condiciones micro y macro ambientales

Salinity tolerance in argentinean population of Bromus catharticus: variability and direct and indirect effects on seedling characters

The aim of this research was to evaluate the salinity tolerance in prairie grass populations at the seedling stage quantifying the variability and the influence of physiological traits related to it. Salinity tolerance, in Bromus catharticus Vahl (prairie grass) populations collected in different environments of the Pampean Phytogeography region (Argentine) was evaluated at the seedling stage, using controlled condition of temperature and light. It was adopted a completely randomized design using 3 plots with three plants each one per population and two levels of treatment: 0 mM and 100 mM NaCl. Morphological, biomass and membrane stability root and shoot traits were studied. A factorial ANOVA with interaction was estimated. Then one way ANOVA for all seedling traits in both treatments allowed estimating variance components, coefficient of genotypic determination (CGD) and variation index (VI). Comparisons between populations were made using Tukey test (at 5% of probability). Phenotypic correlations among traits were calculated and then a path coefficient analysis separated direct and indirect effects at 100 and 0 mM NaCl. No significant interactions “Population × Treatment” were found for any character. The saline stress caused a pairing in the population means for the most traits. Coefficients of variation were mainly higher when the seedlings grew without stress (0 mM) because it allowed a greater potential genotypic expression. The absence of significant interactions denotes a good homeostatic capacity of the prairie grass facing that abiotic stress. Leaf length, shoot length and root dry matter were the variables with the largest direct and indirect effects. Our results showed an increase for them at salt and demonstrated intraspecific variation, possibly in relation with the origin sites. Plants under stress showed a marked resilience, in order to quickly restore the same biomass allocation patterns that occur in non-stress environment.Facultad de Ciencias Agrarias y Forestale

Impact of different cropping conditions and tillage practices on the soil fungal abundance of a Phaeozem luvico

Fungal diversity seems to be a good indicator of ecosystem disturbance and functioning. The purpose of this work was to quantify the fungal population as a sensitive indicator of the changes caused by stubble placement in two tillage systems: reduced tillage (RT) and conventional tillage (CT) with and without cropping. To this end, we determined the effect of soil disturbances such as N fertilization, tillage practice, and cropped area on the soil fungal communities of a Phaeozem luvico of the El Salado river basin (Argentina). Soil samples (at 0-10 cm depth) were collected from a field cultivated with wheat at post-harvest, before sowing and at tillering. The relative abundance of individuals of the fungal population was studied on Nash Snyder and Oxgall agar media after different treatments and assessed as colony forming units (CFU/g of soil). The diversity of the fungal population was studied by Shannon´s index (H). The tillage system showed a marked effect only at post-harvest and the number of propagules was highest under RT for both culture media. The largest values of H were found only at post-harvest when Oxgall agar was used. A significant decrease in the values of H was observed when CT and high fertilization was applied in the wheat cropped area. The relative abundance of individuals of the fungal population was different in soils under the different tillage practices

Clasificación de accesiones de maíz para tolerancia de los tejidos al estrés salino

La salinidad es uno de los estreses abióticos que más severamente afecta al maíz. La obtención de cultivares tolerantes a salinidad sería una estrategia efectiva para superarla. La inhibición del crecimiento por estrés salino puede explicarse a partir de un modelo bifásico: fase osmótica por aumento del potencial hídrico del suelo y fase iónica por incremento de sales en la célula. Las plantas han desarrollado tres mecanismos para tolerar el estrés salino: el primero de tolerancia al estrés osmótico y otros dos mecanismos (asociados con el estrés iónico) que son el de exclusión de Na+ de las hojas y el de tolerancia de los tejidos. Este trabajo evalúa la existencia de variabilidad genética de diferentes genotipos de maíz para la tolerancia de los tejidos. Se probaron 66 poblaciones en un tratamiento salino de 400mM de NaCl durante 3 días. A cada genotipo se le asignó un puntaje en base a una escala de nivel de daño. Dicha escala establecía 7 grados de tolerancia en base al amarillamiento y/o necrosis de los tejidos (grado1 sin daño aparente hasta grado 7 con 100% de necrosis). Se observó una apreciable variabilidad para la tolerancia de los tejidos y se pudieron identificar genotipos que mostraban una buena respuesta que podrían ser empleados en un programa de mejora. En consecuencia, esta prueba podría ser un buen indicador de tolerancia a salinidad asociado al estrés iónico. Los materiales identificados que muestran buen comportamiento podrían ser utilizados en un futuro programa de mejoramiento a estrés salino.Facultad de Ciencias Agrarias y Forestale

Generational Mean Analysis of Salt Tolerance during Osmotic Phase in Maize Seedling

This study details the nature and magnitude of the genetic effects associated with various quantitative characters (morphological and hydric relations) measured in maize seedlings during the osmotic phase of saline stress (100 mM NaCl). Three lines with differential behavior in salt stress: SC2 (tolerant), AFE (susceptible) and LP3 (moderately tolerant) were used to obtain contrasting crosses (SC2 × AFE) and (SC2 × LP3). An analysis of six generational means (P 1, P 2, F 1, F 2, BC1 and B C 2) was applied for each cross. First a scaling test was applied and then a three and six-parameter genetic models were used to estimate various genetic components. In none of the traits studied there was evidence of adequacy to the three parameter model, which indicates important epistatic effects in genetic expression. The dominant genetic effects were greater than the additive ones for all the characters evaluated. LG showed positive and significant differences for [h] in both crosses, indicating the presence of hybrid vigor and its possible use in the improvement. Low value of [d] and high of [h] both significant in SC2 × AFE, indicates existence of genes dispersion between the parental lines. While, for the cross SC2 × LP3, the low and significant value of [d] and not significant value of [h], indicate greater genetic similarity. In the SC2 × LP3 cross, the negative interaction [l ] confirms ambidirectional dominance, while for SC2 × LP3 the positive sign indicates directional dominance. The analysis of tolerance to salinity in the osmotic phase showed a complex polygenic inheritance for the traits used, determined by simple and interaction effects of different magnitudes and significance according to the cross considered.Facultad de Ciencias Agrarias y Forestales (FCAF

Composition and dynamics of the fungal population in a typical Phaeozem luvico in Argentina

he decomposer soil community maintains the arable soil ecosystem for the nutrient turnover. Here, we studied the dynamics of the soil fungal populations in a typical Phaeozem luvico in Argentina and related it to the management practices. Soil samples (at 0–10cm depth) were collected from a field cultivated with wheat, at different sampling times: at post-harvest, before sowing, and at tillering. The relative abundance of individuals in the population on Nash Snyder and Oxgall agar media was assessed as colony forming units (CFU). The fungal population was classified by numerical taxonomy at the different sampling times. The highest values of CFUg−1of soil were found at post-harvest under reduced tillage and differed significantly from those at conventional tillage. The generaTrichoderma,Fusarium,Aspergillus,Penicillium, andFusarium oxysporumwere present in the largest number of samples and discriminated the fungal community between times. This discrimination could be related to alterations in the availability of carbon sources during stubble degradation at post-harvest and before sowing and were of lesser importance at tillering