Maize forage aptitude: Combining ability of inbred lines and stability of hybrids

Breeding of forage maize should combine improvement achieved for grain with the specific needs of forage hybrids. Production stability is important when maize is used for silage if the planting area is not in the ideal agronomic environment. The objectives of the present research were: (i) to quantify environmental and genetic and their interaction effects on maize silage traits; (ii) to identify possible heterotic groups for forage aptitude and suggest the formation of potential heterotic patterns, and (iii) to identify suitable inbred line combinations for producing hybrids with forage aptitude. Forty-five hybrids derived from diallelic crosses (without reciprocals) among ten inbred lines of maize were evaluated in this study. Combined ANOVA over environments showed differences between genotypes (G), environments (E), and their interactions (GEI). Heritability (H2), and genotypic and phenotypic correlations were estimated to evaluate the variation in and relationships between forage traits. Postdictive and predictive AMMI models were fitted to determine the importance of each source of variation, G, E, and GEI, and to select genotypes simultaneously on yield, quality and stability. A predominance of additive effects was found in the evaluated traits. The heterotic pattern Reid-BSSS × Argentine flint was confirmed for ear yield (EY) and harvest index (HI). High and broad genetic variation was found for stover and whole plant traits. Some inbred lines had genes with differential breeding aptitude for ear and stover. Stover and ear yield should be the main breeding objectives in maize forage breeding.Facultad de Ciencias Agrarias y Forestale

Maize forage aptitude: Combining ability of inbred lines and stability of hybrids

Breeding of forage maize should combine improvement achieved for grain with the specific needs of forage hybrids. Production stability is important when maize is used for silage if the planting area is not in the ideal agronomic environment. The objectives of the present research were: (i) to quantify environmental and genetic and their interaction effects on maize silage traits; (ii) to identify possible heterotic groups for forage aptitude and suggest the formation of potential heterotic patterns, and (iii) to identify suitable inbred line combinations for producing hybrids with forage aptitude. Forty-five hybrids derived from diallelic crosses (without reciprocals) among ten inbred lines of maize were evaluated in this study. Combined ANOVA over environments showed differences between genotypes (G), environments (E), and their interactions (GEI). Heritability (H2), and genotypic and phenotypic correlations were estimated to evaluate the variation in and relationships between forage traits. Postdictive and predictive AMMI models were fitted to determine the importance of each source of variation, G, E, and GEI, and to select genotypes simultaneously on yield, quality and stability. A predominance of additive effects was found in the evaluated traits. The heterotic pattern Reid-BSSS × Argentine flint was confirmed for ear yield (EY) and harvest index (HI). High and broad genetic variation was found for stover and whole plant traits. Some inbred lines had genes with differential breeding aptitude for ear and stover. Stover and ear yield should be the main breeding objectives in maize forage breeding.Facultad de Ciencias Agrarias y Forestale

Phenotypic diversity in Argentinian populations of Bromus catharticus (Poaceae): genetic and environmental components of quantitative traits

Genetic and environmental components were analysed in 32 Argentinian populations of Bromus catharticus. The research was based on 39 vegetative and reproductive characters. Constancy (rc) and heritability (h2) ratios were calculated. ANOVAS showed differences between populations for 14 traits, most of them reproductive. Total phenotypic variation was mostly due to the environmental component. Microfloral attributes showed the highest values of rc and h2. The traits average length of the spikelets (LS), average number of florets per spikelet (NFS), and lemma length (LL), which simultaneously reach rc values higher than 1 and h2 values higher than 0.60, could be considered useful in systematic studies. Leaf, stem, and some reproductive characters, linked to propagule production, had plastic responses. However, traits associated with size and shape of propagules and spikelets remained constant. Results suggest that a double strategy is operating: plasticity in some traits (to give greater adaptability), and constancy in other traits related to species stability that are of systematic significance.Facultad de Ciencias Agrarias y Forestale

Phenotypic diversity in Argentinian populations of Bromus catharticus (Poaceae): genetic and environmental components of quantitative traits

Genetic and environmental components were analysed in 32 Argentinian populations of Bromus catharticus. The research was based on 39 vegetative and reproductive characters. Constancy (rc) and heritability (h2) ratios were calculated. ANOVAS showed differences between populations for 14 traits, most of them reproductive. Total phenotypic variation was mostly due to the environmental component. Microfloral attributes showed the highest values of rc and h2. The traits average length of the spikelets (LS), average number of florets per spikelet (NFS), and lemma length (LL), which simultaneously reach rc values higher than 1 and h2 values higher than 0.60, could be considered useful in systematic studies. Leaf, stem, and some reproductive characters, linked to propagule production, had plastic responses. However, traits associated with size and shape of propagules and spikelets remained constant. Results suggest that a double strategy is operating: plasticity in some traits (to give greater adaptability), and constancy in other traits related to species stability that are of systematic significance.Facultad de Ciencias Agrarias y Forestale

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

Regional variation in Argentinean populations of Bromus catharticus (Poaceae) as measured by morphological divergence associated with 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.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.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

Phenotypic diversity in Argentinian populations of Bromus catharticus (Poaceae): genetic and environmental components of quantitative traits

Genetic and environmental components were analysed in 32 Argentinian populations of Bromus catharticus. The research was based on 39 vegetative and reproductive characters. Constancy (rc) and heritability (h2) ratios were calculated. ANOVAS showed differences between populations for 14 traits, most of them reproductive. Total phenotypic variation was mostly due to the environmental component. Microfloral attributes showed the highest values of rc and h2. The traits average length of the spikelets (LS), average number of florets per spikelet (NFS), and lemma length (LL), which simultaneously reach rc values higher than 1 and h2 values higher than 0.60, could be considered useful in systematic studies. Leaf, stem, and some reproductive characters, linked to propagule production, had plastic responses. However, traits associated with size and shape of propagules and spikelets remained constant. Results suggest that a double strategy is operating: plasticity in some traits (to give greater adaptability), and constancy in other traits related to species stability that are of systematic significance.Facultad de Ciencias Agrarias y Forestale

Maize forage aptitude: Combining ability of inbred lines and stability of hybrids

Breeding of forage maize should combine improvement achieved for grain with the specific needs of forage hybrids. Production stability is important when maize is used for silage if the planting area is not in the ideal agronomic environment. The objectives of the present research were: (i) to quantify environmental and genetic and their interaction effects on maize silage traits; (ii) to identify possible heterotic groups for forage aptitude and suggest the formation of potential heterotic patterns, and (iii) to identify suitable inbred line combinations for producing hybrids with forage aptitude. Forty-five hybrids derived from diallelic crosses (without reciprocals) among ten inbred lines of maize were evaluated in this study. Combined ANOVA over environments showed differences between genotypes (G), environments (E), and their interactions (GEI). Heritability (H2), and genotypic and phenotypic correlations were estimated to evaluate the variation in and relationships between forage traits. Postdictive and predictive AMMI models were fitted to determine the importance of each source of variation, G, E, and GEI, and to select genotypes simultaneously on yield, quality and stability. A predominance of additive effects was found in the evaluated traits. The heterotic pattern Reid-BSSS × Argentine flint was confirmed for ear yield (EY) and harvest index (HI). High and broad genetic variation was found for stover and whole plant traits. Some inbred lines had genes with differential breeding aptitude for ear and stover. Stover and ear yield should be the main breeding objectives in maize forage breeding.Facultad de Ciencias Agrarias y Forestale

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