Efectos genéticos en caracteres asociados a la producción de biocombustibles de primera y segunda generación a partir de maíz

Los biocombustibles son obtenidos a partir de material orgánico, que pueden provenir de cultivos con aptitud energética como el maíz mediante la fermentación alcohólica de la fracción amilácea del grano (biocombustibles de primera generación) y de la fracción celulósica de su biomasa (biocombustibles de primera generación). Nuestro objetivo fue determinar la influencia de parámetros de calidad de grano y del rendimiento de bioetanol a partir de grano y de biomasa sobre la producción potencial de bioetanol en la zona maicera núcleo de Argentina, y los efectos genéticos preponderantes en cada caso. Se condujeron experimentos de DBCA con 2 repeticiones, en 3 ambientes del norte de la provincia de Buenos Aires. El material genético consistió en 5 líneas endocriadas de maíz desarrolladas por INTA Pergamino LP2542, LP661, LP29, LP923 y LP214 y sus diez cruzamientos posibles. Se obtuvieron muestras de grano y biomasa, y se determinaron las siguientes variables: Contenido de almidón y de proteína; Relación de molienda; Rendimiento de etanol a partir de grano y de biomasa; Rendimiento de grano y biomasa; Producción de etanol a partir de grano y biomasa; y el índice de cosecha. Se empleó un diseño Dialélico de Griffing, método IV de efectos fijos. Las líneas LP2542 y LP29 presentaron características de calidad deseable para la producción de etanol amiláceo con efectos de ACG altos y positivos. El hibrido constituido por LP 923 y LP2542 concilió los objetivos de alta producción de etanol (L.Ha-1) para los combustibles de primera y segunda generación, preponderando efectos de acción génica de tipo aditivoFil: Farace, María Luján. Argentina. Universidad Nacional del Noroeste..Fil: Percibaldi, Mabel. Argentina. Universidad Nacional del Noroeste..Fil: Eyhérabide, Guillermo. Argentina. Universidad Nacional del Noroeste.

Gene action controlling stability and adaptability in maize

Limited knowledge about the genetic merit of maize landraces contributes to their little use in breeding, al- though some reports pointed them as a source of useful alleles. Repeated cultivation of landraces for many generations could make them a useful germplasm source to enhance yield stability. This study pretends to determine if such statement holds, and to analyze stability in terms of gene action involved. Twenty Argentine landraces were testcrossed to three US and two Argentine elite lines, and evaluated in 13 environments. Effects of general and specific combining ability for grain yield and ecovalence, as well as for regression coefficients of response to en- vironments were also predicted. Non-additivity resulted more important than additivity for controlling ecovalence, and frequently resulted detrimental to stability. Although landraces contributed to ecovalence, their importance was less than that of lines. Testcrosses´ adaptability to environments was variable depending on the line tester considered. Relative greater importance of lines´ general combining ability for ecovalence than landraces’ general combining ability could be attributed to a successful selection for stability during the development of inbred lines. Sixty percent of landraces appeared more adapted to unfavorable environment, which suggests their higher level of rusticity. Argentine lines provided greater stability to their testcrosses than US lines. Correlation between grain yield and stability was mainly dependent upon non additive effects. More productive testcrosses tend to have greater ecovalence (less stability) due to specific combining ability effects. Inbred lines selected for greater general combining ability effect tend to provide their testcrosses higher stability

Maize Nitrogen Use Efficiency: QTL Mapping in a U.S. Dent x Argentine-Caribbean Flint RILs population

This study was aimed to identify quantitative trait loci (QTL) for nitrogen use efficiency(NUE) and related traits in a maize population derived from a cross between two lines with different genetic background (B100 and LP2). Recombinant inbred lines (181) from this population were evaluated under fieldconditions during two growing seasons, and significant(P < 0.01) phenotypic and genotypic variability was detected for most evaluated traits. Two different mapping methods were applied for detecting QTLs. Firstly, a trait by trait approach was performed on across environments, and 19 QTLs were identified.Secondly, a multi-trait multi-environment analysis detected seven joint QTLs. Almost all joint QTLs had inconsistent additive effects from one environment to another, which would reflectpresence of QTL × Environment interaction. Most joint QTLs co-localized with QTLs detected by indi-vidual mapping. We detected consistent additive effects for grain yield per plant and NUE, as well as for biomass and nitrogen harvest index in some joint QTLs, especially QTL-1 and QTL-6. These QTLs had positive and stable effects across environments, and presence of some genes within these QTL intervals could be relevant for selecting for both NUE and grain yield simultaneously. Up today, this is a firstreport on the co-localization of QTLs for enhan-ced allocation of biomass allocation to grains with NUE, and NUE candidate gene identificaion. Fine mapping of these regions could allow to detect additional markers more closely linked to these QTLs that could be used for marker assisted selection for NUE

Classification of argentine maize landraces in heterotic groups

The genetic diversity of maize (Zea mays L) is a valuable and strategic natural resource that plays a key role in the breeding progress. However, exploitation of genetic variability from landraces has not reached a significant level of utilization in breeding programs in Argentina yet. In order to establish their breeding potential, the best 15 out of a group of about 300 landraces from Argentina, were evaluated for various agronomic characters in testcrosses with five lines representing different heterotic groups. Testcrosses were evaluated in nine environments during two growing seasons. A factorial array of those landraces and tester lines was used. Differences for landraces, testers, and landrace x tester interactions were detected for ear diameter and length, ear attachment and plant height, and grain yield. Yield data were further analyzed following additive main effects (landrace and tester) and multiplicative interaction (landrace x tester) models. The first two principal components were significant and accounted for 67% of that interaction. The first axis was consistent with the Argentine flint vs. US dent (Mo17), and US dent (B73) vs. US dent (Mo17) heterotic patterns. The second axis exhibited a contrast between Argentine flint and US dent (B73 or B73 derived line) heterotic groups. The first two principal components of the landrace x tester interaction and mean performance of testcrosses were considered to identify eight landraces as parents of three composite populations

Combining ability evaluation in orange flint lines of maize

In species that show heterosis, information about combining ability with genetically divergent testers is useful to classify the germplasm in heterotic groups. The objective of this study was to evaluate 48 orange flint maize (Zea mays) lines for their combining ability with the testers: sB73 and sMo17 from the Reid x Lancaster pattern and with the flint testers HP3 and P5L2 from the local orange flint pattern during the 1991/92 season at four environments. Analyses of variance were computed for each environment separately and combined across environments for: seed yield, ear height, days to 50% silk, number of ear rows, ear length and diameter, 300 kernels weight, and test weight. Spearman correlation coefficients for grain yield of testcrosses with each tester were computed. Line x tester interactions were highly significant for the majority of the traits and there was no correlation between the merit order of lines based on testcrosses performance. These results suggest the importance of non-additive effects and the ability of the testers to rank the lines.En las especies que exhiben heterosis, el conocimiento de la aptitud combinatoria del germoplasma en cruzamientos con probadores genéticamente divergentes permite su clasificación según grupos heteróticos. El objetivo del presente trabajo fue evaluar 48 líneas de maíz (Zea mays) flint colorado en base a su comportamiento en cruzamientos de prueba con los probadores dentados sB73 y sMo17 del patrón heterótico Reid x Lancaster y con los probadores flint HP3 y P5L2 del patrón heterótico local HP3 x P5L2 en cuatro ambientes durante la campaña 1991/92. Se realizaron los análisis de variancia por ambiente y en forma combinada a través de ambientes para: rendimiento en grano, altura de inserción de espiga, días a floración masculina, número de hileras de grano, largo y diámetro de espiga, peso de 300 granos y peso hectolítrico. Se estimaron los coeficientes de correlación de Spearman para el rendimiento de los cruzamientos de prueba con cada probador. Las interacciones línea por probador fueron altamente significativas para la mayoría de las variables y no hubo correlación entre el ordenamiento de mérito de las líneas basado en su comportamiento en cruzamientos de prueba. Ello refleja la importancia de efectos génicos no aditivos y la capacidad discriminatoria de estos probadores en cruzamientos con las líneas evaluadas.In species that show heterosis, information about combining ability with genetically divergent testers is useful to classify the germplasm in heterotic groups. The objective of this study was to evaluate 48 orange flint maize (Zea mays) lines for their combining ability with the testers: sB73 and sMo17 from the Reid x Lancaster pattern and with the flint testers HP3 and P5L2 from the local orange flint pattern during the 1991/92 season at four environments. Analyses of variance were computed for each environment separately and combined across environments for: seed yield, ear height, days to 50% silk, number of ear rows, ear length and diameter, 300 kernels weight, and test weight. Spearman correlation coefficients for grain yield of testcrosses with each tester were computed. Line x tester interactions were highly significant for the majority of the traits and there was no correlation between the merit order of lines based on testcrosses performance. These results suggest the importance of non-additive effects and the ability of the testers to rank the lines

Evaluación de líneas de maíz flint colorado por aptitud combinatoria

En las especies que exhiben heterosis, el conocimiento de la aptitud combinatoria del germoplasma en cruzamientos con probadores genéticamente divergentes permite su clasificación según grupos heteróticos. El objetivo del presente trabajo fue evaluar 48 líneas de maíz (Zea mays) flint colorado en base a su comportamiento en cruzamientos de prueba con los probadores dentados sB73 y sMo17 del patrón heterótico Reid x Lancaster y con los probadores flint HP3 y P5L2 del patrón heterótico local HP3 x P5L2 en cuatro ambientes durante la campaña 1991/92. Se realizaron los análisis de variancia por ambiente y en forma combinada a través de ambientes para: rendimiento en grano, altura de inserción de espiga, días a floración masculina, número de hileras de grano, largo y diámetro de espiga, peso de 300 granos y peso hectolítrico. Se estimaron los coeficientes de correlación de Spearman para el rendimiento de los cruzamientos de prueba con cada probador. Las interacciones línea por probador fueron altamente significativas para la mayoría de las variables y no hubo correlación entre el ordenamiento de mérito de las líneas basado en su comportamiento en cruzamientos de prueba. Ello refleja la importancia de efectos génicos no aditivos y la capacidad discriminatoria de estos probadores en cruzamientos con las líneas evaluadas

Influencia de diversos factores en la determinación del contenido de cenizas, fósforo, magnesio y sodio en una muestra de pasturas (Bothriocloa laguroides)

p.151-156Con el objeto de estudiar el efecto del tamaño del crisol, la posición de este en la mufla y la cantidad de muestra empleada, sobre la evaluación del contenido de cenizas, fósforo, magnesio y sodio, se diseño un experimento factorial con tres factores a 2 niveles, con 4 repeticiones. Se utilizó en el ensayo una muestra de pastura (Bothriocloa laguroides, estado reproductivo, fracción tallo). Las muestras fueron calcinadas a 500°C durante 5 horas, las cenizas disueltas en HCI 4 F, y diluidas a 25 mi con agua destilada, el contenido de P se determinó colorimetricamente por el método del azul de molbdeno, el de Na por fotometría de llama, y el de Mg por de absorción atómica. Una interacción significativa (P menor a 0,05) se observó entre la posición del crisol en la mufla y la cantidad de muestra, en relación al contenido de P, Mg y Na. El análisis de contenido de Na mostró una correlación significativa (P menor a 0,05) con respecto a la cantidad de muestra y al tamaño del crisol. El tamaño de crisol influyó significativamente (P menor a 0,01) en el contenido de cenizas. Se condujo un ensayo de recuperación de fósforo para distintas relaciones Ca0-P205, no observándose una correlación significativa (P-0,05)

Epidemiologisches Bulletin 39 / 2011

Broadening the genetic base of maize breeding program is a significant concern for plant breeders, since it restricts the magnitude of genetic gain. Identification of promissory exotic elite maize (Zea mays L) germplasm would be useful to increase the genetic variation within typically used heterotic groups and to improve the forage yield and quality. This study is aimed to assess the genetic potential of a group of elite maize landraces to improve forage yield and quality related traits and to broaden the genetic base of three temperate heterotic groups. Mean values and landrace general combining ability effects (GCA ) revealed that some landraces could be considered as a valuable genetic resource to broaden the current genetic base through introgression of forage yield and quality favorable alleles. When stover and ear dry matter yield were considered, ARZM17035 was the best landrace since it produced the best performing landrace × inbred line crosses that also were stable across environments. Addi- tionally, this landrace showed high GCA . Considering quality traits, ARZM07134 was the most promising source of favorable alleles. The use of B73 as tester in a recurrent selection scheme would be the most efficient strategy, since both mentioned landraces crossed to B73, showed the highest yield and quality values. Additionally, evalu- ated traits were mainly controlled by additive effects, so it is expected to obtain a positive response by selectio