Quantification of critical factors affecting fitness of the sugary1 mutant in maize

Fitness of sugary1 (su1) is affected by some critical traits that depend on the genotypes and environments, while their effects have not been quantified with convincing statistical methods. The objective of this work was to identify and quantify the critical factors of su1 fitness with different genotypes and environments. We used two pairs of field corn inbreds that differentially affected su1 viability to develop F1, F2, BC1 and BC2. After selfing, Su1 and su1 kernels were evaluated under controlled environmental conditions and in field trials. Multiple regressions showed that dry weight of juvenile plant was affected by early vigour (plant size, colour and health) and emergence in cold conditions; ear weight by plant appearance, number of plants and chlorophyll content; number of ears by plant appearance, number of plants, chlorophyll content and female flowering; and kernel weight by ear weight, number of plants, row number and ear length. The main critical factors for su1 fitness were early vigour and emergence under cold conditions at initial stages, while several adult traits were related with final fitness.Research was supported by the Spanish Plan for Research and Development (project code AGL2007-64218/AGR and AGL2010-22254) and the Diputación Provincial de Pontevedra. A Djemel acknowledges his fellowship from the Spanish Council for Scientific Research (CSIC).MICINNDiputación Provincial de PontevedraCSICPeer reviewe

Defense mechanisms of maize against pink stem borer

The pink stem borer (Sesamia nonagrioides Lef.) is the most important pest of maize (Zea mays L.) in northwestern Spain. The objective of this work was to evaluate defense mechanisms against Sesamia in 10 inbred lines and the 10-parent diallel among these inbreds. Hybrids and inbred lines were tested over 2 yr in northwesternSpain under natural and artificial infestations. Yield of infested and non infested plants per plot were computed to calculate yield loss caused by the pink stem borer attack. Principal component analyses for stem damage traits and for ear damage traits were made for each infestation condition. From the principal component analysis, an index was computed to measure stem damage and ear damage. Damage index under artificial infestation was used to evaluate antibiosis while antixenosis was detected when damage index of each genotype was compared under artificial and natural infestation. The regressions of yield loss on the damage index were used to separate the genotypes into four groups according to the possession of antibiosis and/or tolerance mechanisms. A509, A661, EP31, F7, PB60, and Z77016 showed stem antibiosis. A637, A661, EP31, F7, and PB60 exhibited stem tolerance. A509, A661, and EP31 stood out by their ear antibiosis. A637, A661, F7, and PB60 were tolerant to ear damage. We conclude that the three mechanisms of defense to the pink stem borer attack (antixenosis, antibiosis, and tolerance) were found among inbred lines and hybrids. A multitrait selection scheme using damage traits and yield could improve the defense level against pink stem borer.Research supported by Dep. of Education of the Autonomous Government of Galicia (project XUGA40301B95Xunta de GaliciaN

Contribution of autochthonous maize populations for adaptation to European conditions

Early vigor, earliness and cold tolerance are the main potential contributions of European maize (Zea mays L.) for breeding programs for adaptation to areas with short growing seasons and cold springs. The objective of this research was to determine the potential contributions of populations from different European regions to breeding for adaptation. Six Spanish and six French maize populations differing on variability for earliness, vigor and cold tolerance were crossed in a complete diallel without reciprocals. The populations and their crosses were evaluated in the field and in a cold chamber. Minimum temperatures were the main environmental trait affecting genotype × environment interaction, probably due to the cold sensitivity of the genotypes with the best performance in the field. The best population cross, based on specific heterosis for adaptation-related traits in the field, was Viana × Rastrojero, but this cross was cold sensitive. Tuy × Lazcano should be the best choice for a breeding program for adaptation, based on performance in the field and cold tolerance. As conclusions, there was variability for earliness, vigor and cold tolerance among the populations and crosses involved in this study, being tolerant to cold conditions the populations with medium growing cycle originated in areas with short growing seasons. The highest yielding crosses were cold sensitive.Research supported by the Ministry of Science and Technology (Ref. HF1999-0138), the Ministère de l’Education Nationale et de la Recherche, the Committee for Science and Technology of Spain (Project AGL2004-06776), the Autonomous government of Galicia (PGIDIT04RAG403006PR), the Excma. Diputación Provincial de Pontevedra, and the European Union (RESGEN 88 CT96).Peer reviewe

Combining abilities for maize stem antibiosis, yield loss and yield under infestation and no infestation with pink stem borer

The pink stem borer (Sesamia nonagrioides Lef.) is the main pest of maize (Zea mays L.) in northwestern Spain. Little is known about combining ability for antibiosis and tolerance to this pest. Therefore, the objectives of this work were to estimate general combining ability (GCA), specific combining ability (SCA), and reciprocal effects for stem damage traits, yield, and yield loss by a complete diallel of 10 inbreds and to determine the most useful trait for evaluating the level of defense to pink stem borer. The diallel design was evaluated for 2 yr for stem damage traits, yield loss, and for yield under two conditions, infestation with Sesamia nonagrioides and non infestation. For all stem damage traits, GCA was significant, while SCA and reciprocal effects were not significant. This indicated that, for this set of inbreds, only additive effects were important for stem antibiosis. GCA and SCA effects were significant, in at least one trial, for yield under both infestation conditions and for yield loss. Reciprocal effects were significant for yield of infested and non infested plants in 1995. The lack of concordance among lines that exhibited the most favorable GCA effects for stem antibiosis, yield loss, and yield under infested conditions and the low correlation coefficient between SCA effects for yield under infested and non infested conditions showed that yield under infested conditions is the best trait for evaluating the level of defense against pink stem borer attack.Research supported by the Committee for Science and Technology of Spain (project AGF92-0161) and by the Department of Education of the Autonomus Government of Galicia (project XUGA 40301B95).MCYTXunta de GaliciaN

Gallástegui: el nacimiento de la genética en España

Conferencia pronunciada por el autor con motivo del Día do Científico Galego, RAGC, 22.- Abril 2010.Peer reviewe

The influence of soil in agricultural experiments

9 páginas.- 2 figuras.- 5 tablas.[EN] Plant breeding is an activity aimed to assess which genotype is the best within a population of new genotypes. If the soil were completely homogeneous, a breeder could easily detect the best plants from a field experiment, but even the apparently most homogeneous soil has a considerable degree of heterogeneity. To cope with this inconvenience a branch of statistics has been developed: the design of experiments. The simplest experimental design is the completely random design, which is appropriate when there are no sources of variation other than treatment effects. However, in many cases we have to use more complex designs like randomized complete blocks, factorial designs, latin squares, split plots, spatial designs, etc. In all cases, we must pick the design that minimizes experimental error, with heterogeneity of soil in the case of agricultural experiments being one of the main causes, if not the main, that influences its magnitude.[ES] La mejora genética vegetal tiene como objetivo detectar el mejor genotipo en una población de genotipos nuevos. Si el suelo fuera completamente homogéneo, el mejorador detectaría fácilmente las mejores plantas en un experimento de campo, pero incluso el suelo que aparentemente es homogéneo, tiene una heterogeneidad considerable. Para resolver estos problemas se ha desarrollado una rama de la estadística que es el diseño de experimentos. El diseño más simple es el diseño completamente aleatorizado, apropiado para aquellos casos en los que los efectos de los tratamientos son las únicas fuentes de variación. Sin embargo, en muchos casos hay que usar diseños más complejos como el de bloques completos al azar, diseños factoriales, cuadrados latinos, parcelas divididas, diseños espaciales, etc. En todos los casos hay que elegir el diseño que minimiza el error experimental. En el caso de los experimentos agrícolas la heterogeneidad del suelo es seguramente la principal causa que influye sobre la magnitud del error experimental.Peer reviewe

Biodiversidad de cultivos en la zona atlántica

5 páginas, 3 tablas -- Ponencia presentada al Seminario sobre Biodiversidad Vegetal en el Sistema Agroforestal Atlántico, celebrado en Pontevedra (España) entre el 27 y el 28 de octubre de 2010.Una agricultura potente se basa en semillas de alta productividad combinadas con unas técnicas de cultivo adecuadas. Al principio de la agricultura, y durante muchos siglos, el propio agricultor era el mejorador. Con el advenimiento de la agricultura científica apareció la especialización y la selección de las semillas pasó a ser competencia de los mejoradores profesionales. Para poder desarrollar esas semillas de alta productividad, es fundamental que el mejorador disponga de la mayor cantidad posible de variabilidad genética del cultivo en cuestión. Si bien mucha de esa variabilidad se ha perdido, aún se conserva mucha, bien en los bancos de germoplasma, bien en manos de los agricultores.Peer reviewe

Coliflor

3 páginas.La historia conocida de la coliflor va estrechamente ligada a la del bróculi (Brassica oleracea varo italica Plenck), con el que comparte un patrimonio genético común. Tanto es así que en muchas zonas el bróculi recibe el nombre de coliflor de invierno, denominándose entonces a la verdadera coliflor como coliflor de verano. Si bien no hay una teoría aceptada en su totalidad, se cree que una forma silvestre anual de B. oleracea fue domesticada en el Mediterráneo oriental hace varios miles de años como un bróculi primitivo. Este bróculi ancestral se expandió, por una parte, hacia China, y por otra, por todo el Mediterráneo, hibridándose aquí con otras formas de B. oleracea. En los últimos 500 años, más o menos, se comenzó la selección buscando los tipos que hoy son más comunes: por un lado hacia una gran inflorescencia terminal blanca muy densa (la pella), lo que originó las coliflores, y por otro hacia inflorescencias verdes menos compactas: los bróculis.Peer reviewe

Maíz dulce

3 páginas.El maíz dulce, tal como se usa hoy en el mundo occidental, es un desarrollo de los agricultores del este norteamericano de los siglos XVIII y XIX. Según la leyenda, este cultivo fue introducido en 1779 entre los colonos de Nueva Inglaterra con el nombre de maíz «paoon» por el teniente Richard Bagnal, quien, al volver de la expedición del General Sullivan contra las Seis Naciones (una confederación de pueblos iroqueses), trajo consigo algunas mazorcas de dicho maíz. El maíz «papoon» fue cultivado privadamente entre 1779 y 1828, año en que Thorburn lo puso a la venta. La primera variedad con nombre propio (Darling's Early) apareció en 1844 y fue producida cruzando maíz dulce (probablemente la variedad traída por Richard Bagnal) con maíz normal. Otra primitiva variedad (Old Colony) fue producida de un modo similar. A partír de estas primeras variedades de maíz dulce, y mediante cruzamiento de ellas con variedades indias, se obtuvieron cientos de cultivares. En el momento de comenzar los primeros trabajos de autofecundación y desarrollo de híbridos había aproximadamente 180 variedades blancas de polinización libre y 50 amarillas, si bien muchos de los nombres se referían a una misma variedad. Los primeros programas de autofecundación y cruzamiento comenzaron hacia 1920 en Indiana y Connecticut. El primer híbrido cultivado extensamente fue Redgreen, desarrollado en Connecticut y entregado a la industria en 1924. El híbrido Golden Cross Bantam, puesto a disposición de los agricultores en 1933 por la Universidad de Purdlle (Indiana), demostró su superioridad sobre las variedades de polinización libre tras unas tremendas epidemias de marchitez bacteriana que tuvieron lugar en 1932 y 1933. Golden Cross Bantam mostró, en adición, gran capacidad productiva y una excelente calidad, por lo que su cultivo se extendió con gran rapidez y sirvió, además, para que los híbridos simples se popularizaran rápidamente.Peer reviewe

Heterosis in crosses between American and Spanish populations of maize

Most maize (Zea mays L.) crosses in te mperate zones use the heterotic pattern Reid ✕ Lancaster, but in western Europe the pattern U.S. dent ✕ European flint has also been used. This study was undertaken to determine the heterotic relationships between Spanish and U.S. Corn Belt germplasm to identify a heterotic pattern for a comprehensive system of breeding. Four early U.S. Corn Belt and five Spanish populations were crossed in a diallel series that was tested for three years at two locations. Using heterosis for yield as the measure of dissimilarity, a phenogram showed the existence of three groups of populations: U.S. Corn Belt, northern Spain, and southern Spain. Two composites were formed, one with germplasm from northern Spain (EPS6) and the other with germplasm from southern Spain (EPS7), that were subjected to one cycle of S1 recurrent selection. The yield gains were 10.4 and 9.4% for EPS6 and EPS7, respectively. The mid-parent heterosis was 32.7%, much greater than predicted (17.7%). Spanish germplasm can be a useful addition to maize breeding programs of temperate zones, enhancing the genetic base of the material being used.Peer reviewe