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8 Pag., 6 Tabl. ; [EN] Early-maturing flint maize germplasm could be an important alternative for the development of new early-maturing commercial hybrids adapted to cooler summer regions. Our objective was to evaluate the performance of flint populations in crosses with four testers from different heterotic groups, as sources of new potential inbred lines. Ten flint maize populations were crossed to four inbred testers representing Reid Yellow Dent, Lancaster Sure Crop and two Spanish flint heterotic groups. Topcrosses were evaluated in four environments in north eastern Spain in 2001 and 2002. The main type of gene action expressed was additive. All populations except Enano Norteño/Vasco and Hembrilla Norteño/Vasco, had a higher specific combining ability in crosses with Reid Yellow Dent or Lancaster Sure Crop testers. Average yields were better when populations were crossed with dent lines rather than with the flint inbred line EP42. These results could be useful in the development of new inbred lines that would increase genetic variability present in commercial European flint maize. ; [ES] La evaluación de germoplasma liso precoz de maíz podría ser importante como una alternativa para el desarrollo de nuevos híbridos comerciales precoces adaptados a regiones templadas y potencialmente útiles para producir grano de alta calidad. Nuestros objetivos fueron evaluar el potencial de poblaciones lisas precoces y estimar el rendimiento de este germoplasma en cruzamientos con probadores de diferentes grupos heteróticos para el desarrollo de híbridos precoces de maíz grano. Diez poblaciones de maíz grano se cruzaron con cuatro probadores que representan Reid Yellow Dent, Lancaster Sure Crop y dos grupos heteróticos europeos. Los cruzamientos fueron evaluados en cuatro ambientes en el noreste de España durante 2001 y 2002, siendo la expresión génica expresada aditiva. Todas las poblaciones cruzadas, excepto Enano Norteño/Vasco y Hembrilla Norteño/Vasco, mostraron una mayor aptitud combinatoria específica en cruzamientos con probadores Reid Yellow Dent o Lancaster Surecrop. El mejor rendimiento medio se produjo cuando todas las poblaciones se cruzaron con las líneas dentadas en lugar de con la línea lisa EP42. Estos resultados podrían ser útiles para desarrollar nuevas líneas puras que incrementen la variabilidad presente en el maíz liso comercial europeo. ; Part of this work was financed by the Spanish Ministry of Education and Science project AGL2007- 64218/AGR, INIA (RF2007-00007-C05-04) and by Basque Government funds. ; Peer reviewed

The definitive version is available at http://www.inia.es/sjar ; Eight cycles of divergent mass selection for flowering time were performed in the synthetic maize (Zea mays L.) population Lazcano (EZS9, from Guipuzcoa, Spain). A trial with a randomised block design plus three replicates was then performed at two locations in northeastern Spain, and over two years, to compare flowering time in the original population and the material produced in the eight selection cycles. Linear regression coefficients were determined to estimate the average rate of selection response per cycle. Genetic gains with respect to the vegetative cycle and other major agronomic traits were obtained. Direct selection responses were significant and grain yield maintained. No negative correlated responses were obtained for any agronomic trait. Divergent mass selection for early flowering was therefore found to be efficient in this synthetic population ; This work was partially supported by the Spanish Ministry of Education and Science project AGL2004-06776-C02, and by Basque Government funds. ; Peer reviewed

Available online at www.inia.es/sjar ; European flint × U.S. dent is a common heterotic pattern used in early maize (Zea mays L.) breeding programs in Europe. Two maize synthetic populations, EZS1 (formed from four Spanish flint populations), and EZS2 (formed from four American dent populations), were developed at Zaragoza, Spain. The synthetics showed heterotic behavior and were subjected to six cycles of S1 recurrent selection for increased grain yield and reduced lodging. The objective of this research was to study the effectiveness of selection on grain yield and other agronomic traits in both synthetics. The original populations, EZS1C0 and EZS2C0, and the six cycles of selection of both, were evaluated in two locations during two years. Over six selection cycles, average yield of EZS1 and EZS2 increased by 0,82 Mg ha-1 and 0.93 Mg ha-1 per cycle, respectively, and lodging decreased by 2.76% and 2.44% per cycle, respectively. Gains due to selection for all traits in both synthetics were significant. It was concluded that S1 selection was effective in improving yield and reducing lodging in each synthetic to start a reciprocal recurrent selection. ; Part of this work was financed in the frame of Ministry of Education and Science of Spain project AGL2004-06776-C02-02 and for Basque Government funds. ; Peer reviewed

One hundred landraces of maize from Northern Spain were characterized on the basis of twenty-two morphological traits, and seventeen ecological variables (climatic, edaphic and topographic) associated with the collection site. High broad-sense heritabilities (≥ 0.6) were found for plant height, ear height, ear node number, ear length, mid-ear diameter, rows of kernels, kernels per row, cob weight and days to silking. Seven different groups were obtained with cluster analysis using plant and cycle traits, and discriminant analysis showed that leaf area, ear shape, tassel branches, rows of kernels, plant height, cob weight, and ear length were the most important traits for taxonomic classification. Seven populations with promising breeding value were detected. ; This work was supported by the Department of Agriculture of the Basque Government (Spain) and partially by CICYT (Project AGF98-0968-C02-2) ; Peer Reviewed

7 Pags., 3 Tabls., 1 Fig. ; S-1-progeny recurrent selection has proved effective improving the performance per se and the general combining ability (GCA) of maize (Zen mays L.) synthetic populations. Two maize synthetics, EZS1, a flint-type of Span ish origin, and EZS2, a dent population of North American origin, were produced al Zaragoza, Spain, and subjected to two cycles of S-1 recurrent selection for increased grain yield and reduced lodging and grain moisture. Our objectives were i) to assess the effect of S-1 recurrent selection on the heterotic behaviour of these synthetics, and) to evaluate the changes in combining ability after selection using as testers the populations themselves and three diverse inbred lines. The entries from a diallel mating design of the three cycles (0,1, and 2) of the two populations were tested in five environments. Testcrosses involving the three selection cycles of both synthetics and three diverse inbred testers were evaluated in three environments. Selection in both synthetics resulted in more productive populations, with less lodging, and no important negative responses in other agronomic trails. Improvements were less evident in the crosses of the populations, with significant GCA change only in EZS2 for lodging. Gains due to selection for grain yield in both synthetics and for lodging in EZS2 were significant, but the gains were not consistent across testers. Selection was effective in improving the populations per se. and the best testcrosses were not significantly different from the hybrid checks used for comparison. ; The senior author thanks the Basque Government for a graduate research assistant-ship. ; Peer reviewed

6 Pags., 5 Tabls. ; The most important pest of maize (Zen mays L.) in North America and Europe is the European corn borer (Ostrinia nubilalis Hbn). However, in southern Europe another corn borer species, the pink stem borer (Sesamia nonagrioides Lef.), also causes significant damage to maize. The damage caused by the pink stem borer in the northwest of Spain was not important a few years ago, but today this damage has increased considerably. Few studies about this pest have been made thus far. The first objective of this work was to study the population quantify and seasonal appearance of Sesamia nonagrioides in this area. Two trials were carried out in two years under natural field conditions with different sowing dates, thus covering the damage at different stages where the plant-insect relationship could change. The results showed that the attacks varied in intensity depending on the year and sowing date. Early sowing could be a good method for cultural control of Sesamia nonagrioides because the material is too mature and escaped borer attack. Although cultural control could be effective in preventing or reducing the damage, genetic resistance is another alternative that could be used alone or joined with other control components for integrated pest management. The first step in this insect-resistance breeding program is to identify sources of resistance. Consequently, the second objective was to study the resistance/tolerance of twenty maize inbred lines under artificial infestation conditions with Sesamia nonagrioides. The inbred lines were evaluated for resistance and other agronomic traits. Significant differences were found for all traits. The inbred lines were divided according to maturity groups: early and late. Early maturing inbreds had the greatest damage. The early inbreds EP37, W153R and CM105 and the late inbreds Va26 and W64A showed the best resistance to the pest. Thus, they could be promising sources of resistance or tolerance to pink stem borer. These lines may be suitable far use directly in the formation of resistant hybrids and new resistant inbred lines. Further, they and others could be used for the development of resistant synthetics, which could become the base material to obtain resistant varieties to Sesamia nonagrioides. ; This work was supported by the Committee for Science and Technology of Spain (project AGR89-0537) and the Autonomous Government of Galicia (project XUGA40301A90). ; Peer reviewed

The most important pest of maize (Zea mays L) in North America and Europe is the European com borer (Ostrinia nubilalis Hbn). However, in southern Europe another com borer species, the pink stem borer (Sesamia nonagrioides Lef.), also causes significant damage to maize. The damage caused by the pink stem borer in the northwest of Spain was not important a few years ago, but today this damage has increased considerably. Few studies about this pest have been made thus far. The first objective of this work was to study the population quantity and seasonal appearance of Sesamia nonagrioides in this area. Two trials were carried out in two years under natural field conditions with different sowing dates, thus covering the damage at different stages where the plant-insect relationship could change. The results showed that the attacks varied in intensity depending on the year and sowing date. Early sowing could be a good method for cultural control of Sesamia nonagrioides because the material is too mature and escaped borer attack. Although cultural control could be effective in preventing or reducing the damage, genetic resistance is another alternative that could be used alone or joined with other control components for integrated pest management. The first step in this insect-resistance breeding program is to identify sources of resistance. Consequently, the second objective was to study the resistance/tolerance of twenty maize inbred lines under artificial infestation conditions with Sesamia nonagrioides. The inbred lines were evaluated for resistance and other agronomic traits. Significant differences were found for all traits. The inbred lines were divided according to maturity groups: early and late. Early maturing inbreds had the greatest damage. The early inbreds EP37, W153R and CMI05 and the late inbreds Va26 and w64A showed the best resistance to the pest. Thus, they could be promising sources of resistance or tolerance to pink stem borer. These lines may be suitable for use directly in the formation of resistant hybrids and new resistant inbred lines. Further, they and others could be used for the development of resistant synthetics, which could become the base material to obtain resistant varieties to Sesamia nonagrioides. ; This work was supported by the Committee for Science and Technology of Spain (project AGR89-0537) and the Autonomous Government of Galicia (project XUGA40301A90). ; Peer reviewed

7 Pags., 9 Tabls. ; The European corn borer (Ostrinia nubilalis Hbn) is an important insect pest of maize (Zea mays L.) in Europe. However, the larvae of pink stem borer (Sesamia nonagrioides Lef.) produce important damage to the stems, especially in Southern Europe. The first step in an insect-resistance breeding program is to identify sources of resistance. The objective of this work was to study the resistance/tolerance of several populations of maize to attack by corn borers in general, and of Sesamia nonagrioides in particular. Twenty landraces of maize were evaluated for two years at two locations under natural infestation. In one location most of the larvae that were found belonged to Sesamia while in the other location the larvae of Ostrinia were more abundant. Agronomic and resistant traits were analyzed in all trials and the best varieties for resistance. along with new material, were evaluated further under artificial infestation conditions with Sesamia nonagrioides. The extraearly and early material suffered less borer damage than the late and midseason material, because the early populations probably escaped the second brood of borers. Moreover, the varieties with small proportion of damaged stems come from the Ebro valley. The germplasm of this area. then, could be a good source of resistance or tolerance to the borers. However, it showed a low yield. The EPS7(S)C2 synthetic also had good resistance under artificial infestations with Sesamia nonagrioides. Further, it showed better yield than the landraces because two cycles of S1 recurrent selection for yield have been carried out in this synthetic. Therefore EPS7(S)C2 could be the base material in a breeding program to obtain resistant varieties to the pink stem borer. ; This workk was supportcd by the Commitee for Science and Technology (Comisión Inteministerial de Ciencia y Tecnología) of Spain (projecl AGR89-0537) and the Department of Education of the Autonomous Government of Galicia (project XU-GA40301A90). ; Peer reviewed

The European corn borer (Ostrinia nubilalis Hbn) is an important insect pest of maize (Zea mays L.) in Europe. However, the larvae of pink stem borer (Sesamia nonagrioides Lef.) produce important damage to the stems, especially in Southern Europe. The first step in an insect-resistance breeding program is to identify sources of resistance. The objective of this work was to study the resistance/tolerance of several populations of maize to attack by corn borers in general, and of Sesamia nonagrioides in particular. Twenty landraces of maize were evaluated for two years at two locations under natural infestation. In one location most of the larvae that were found belonged to Sesamia while in the other location the larvae of Ostrinia were more abundant. Agronomic and resistant traits were analyzed in all trials and the best varieties for resistance. along with new material, were evaluated further under artificial infestation conditions with Sesamia nonagrioides. The extraearly and early material suffered less borer damage than the late and midseason material, because the early populations probably escaped the second brood of borers. Moreover, the varieties with small proportion of damaged stems come from the Ebro valley. The germplasm of this area. then, could be a good source of resistance or tolerance to the borers. However, it showed a low yield. The EPS7(S)C2 synthetic also had good resistance under artificial infestations with Sesamia nonagrioides. Further, it showed better yield than the landraces because two cycles of S1 recurrent selection for yield have been carried out in this synthetic. Therefore EPS7(S)C2 could be the base material in a breeding program to obtain resistant varieties to the pink stem borer. ; This work was supported by the Committee for Science and Technology of Spain (Project AGR89-0537) and the Department of Education of the Autonomous Government of Galicia (Project XUGA40301A90). ; Peer reviewed

The definitive version is available at: http://www.sciencedirect.com/science/journal/02612194 ; In Europe, corn borer attack is the main biotic stressor for the maize (Zea mays L.) crop. European corn borer (Ostrinia nubilalis Hbn.) is the most important maize pest in central and north Europe, while pink stem borer (Sesamia nonagrioides Lef.) is predominant in warmer areas of southern Europe. The objective of this study was the evaluation of the European Maize Union Landrace Core Collection (EUMLCC) for yield under infestation with European corn borer (O. nubilalis) and pink stem borer (S. nonagrioides). Eighty-five landraces from Germany, Spain, France, Greece, Italy, and Portugal were evaluated, under corn borer infestation, for yield, grain moisture, and days to flowering at two locations in Spain. Landraces were evaluated separately in four trials that corresponded to four maturity groups. In each maturity group, there were significant differences among landraces for yield of infested plants. Extra-early landraces, ESP0090214, FRA0410010, and ESP0070339; early landraces, FRA0410022, and ESP11985022; midseason landraces, PRT00100392 and ESP11981047; and late landraces, PRT00100569 and PRT00100530, were promising sources of high-yielding maize under corn borer infestation and showed relative earliness within their maturity groups. ; Research supported by the European Union (RESGEN-CT96-088) and the Excma. Diputación Provincial de Pontevedra, Spain. A. Butrón and G. Padilla acknowledge the support that they got from the Spanish Ministry for Science and Technology and the 'Cabildo de la Isla de La Palma', respectively. ; Peer reviewed

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 reviewed