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Simple Summary: Maize is one of the major crops of the world for feed, food, and industrial uses. It originated in Central America and was first introduced into Europe at the end of the 15th century. Due to its adaptability, farmers and breeders across Europe have developed a wide diversity of local maize varieties with different characteristics over the past centuries. Many of these are conserved in genebanks' seed collections, but little is known about their specific characteristics. Here, we present results obtained by the European Evaluation Network for Maize, a private–public partnership with partners from nine countries aimed at promoting the valorization of maize genetic resources in breeding programs. The work describes the selection and the genetic and phenotypic evaluation of a collection of 626 maize landraces preserved in European genebanks, providing evidence for historic introductions and geographic adaptation. In a world where climate change, rising food prices, and other issues are affecting food security and the environment, the conservation and use of crop diversity is becoming increasingly important. The results of our study will facilitate the use of maize genetic resources in breeding for resilience to climate change, for sustainable agriculture, food security, and food quality. The ECPGR European Evaluation Network (EVA) for Maize involves genebanks, research institutions, and private breeding companies from nine countries focusing on the valorization of maize genetic resources across Europe. This study describes a diverse collection of 626 local landraces and traditional varieties of maize (Zea mays L.) from nine European genebanks, including criteria for selection of the collection and its genetic and phenotypic diversity. High-throughput pool genotyping grouped the landraces into nine genetic groups with a threshold of 0.6 admixture, while 277 accessions were designated admixed and likely to have resulted from previous breeding activities. The grouping correlated well with the geographic origins of the collection, also reflecting the various pathways of introduction of maize to Europe. Phenotypic evaluations of 588 accessions for flowering time and plant architecture in multilocation trials over three years confirmed the great diversity within the collection, although phenotypic clusters only partially correlated with the genetic grouping. The EVA approach promotes conservation of genetic resources and opens an opportunity to increase genetic variability for developing improved varieties and populations for farmers, with better adaptation to specific environments and greater tolerance to various stresses. As such, the EVA maize collection provides valuable sources of diversity for facing climate change due to the varieties' local adaptation. [ABSTRACT FROM AUTHOR]

Climate change is expected to affect agriculture. Yield stability across environments is a critical breeding goal when dealing with unstable climate and input reductions in farming systems. The objective of this study was to determine climatic and genetic factors contributing to genotype (G), environment (E), and genotype x environment (GE) variability for maize (Zea mays L.) grain yield under some stress conditions like drought, cold, and pest attack. A large sample of Spanish maize populations was evaluated along with checks at three diverse locations during 3 yr. Factorial regression was performed to obtain a biological explanation of the G, E, and GE interaction for yield. The commercial hybrids had more yield and stability than most populations; therefore, breeding programs focusing on yield have released hybrids with high yield and stability under stress conditions. The populations with a reasonable compromise between yield and stability were Andoain and Lira. The main genotypic covariate was kernel depth, followed by ear length, although other covariates were important for each location. The main climatic covariates for yield were related to days with mean temperature over 15[degrees]C and maximum temperature in September, but they were not consistent across locations. Therefore, if yield under stress conditions is a breeding goal, several climatic variables, especially those related to high temperatures, and genotypic traits such as kernel depth and ear length should be considered. doi: 10.2135/cropsci2008.12.0695

Breeding of maize (Zea mays L.) in the Atlantic coast of Europe has focused on developing hybrids to exploit heterosis between flint and dent germplasm. Flint x flint hybrids could have some advantages because of their earliness and early vigor that are important in short growing season areas. The objective of this work was to study the adaptation of a set of 10 flint varieties crossed to flint and dent testers and in a diallel design to check the feasibility of a breeding program to obtain flint hybrids well adapted to European Atlantic conditions. In the testcrosses, general combining ability (GCA) of the flint tester EP42 for kernel moisture at harvest and days to silking was lower than those of dent testers. Improvement of flint varieties for combining ability with inbred line EP42 could be done to obtain earlier flint x flint hybrids with a better dry-down rate than flint x dent hybrids. Diallel entries were analyzed following Analysis II of Gardner and Eberhart. Variety and heterosis effects were significant for all traits. Varieties Gallego and Norteno, besides having large variety effects, also showed intermediate variety heterosis for adaptive traits and they would be the best adapted varieties to include in breeding programs. The cross 'Gallego x Basto/Enano levantino' combined the best yield and good specific heterosis for adaptive traits. Thus, flint hybrids to he grown in short season areas could be obtained following this heterotic pattern.

Most maize (Zea mays L.) hybrids cultivated in Europe follow the heterotic pattern European flint x Corn Belt dent. However, at present, no commercial hybrids have been obtained from European flint inbreds exclusively. A flint x flint heterotic pattern could be an alternative to use in breeding programs to obtain early maturity, high-yielding hybrids, potentially useful for producing high quality flours. The objective of this work was to search for heterotic patterns within flint germplasm adapted to temperate conditions. Ten open-pollinated flint maize cultivars were crossed in a diallel design without reciprocals and evaluated in four environments in northwestern Spain. Cultivar effects explained most of the sum of squares for traits analyzed, except for yield. Crosses yielded 30% more than parental cultivars. Yield of crosses ranged from 3.94 to 5.61 Mg [ha.sup.-1]. Midparent heterosis values ranged from 2.5 to 64.7%. The crosses 'Gallego' x 'Basto/Enano Levantino' and Basto/Enano Levantino x 'Longfellow' showed high heterosis and the best averages for grain yield. On the basis of these results, these crosses could be included in a recurrent reciprocal selection breeding program to increase heterosis among the cultivars and improve their hybrids. A cluster analysis made with midparent heterosis for grain yield as a measure of distance revealed that the flint germplasm probably had similar origins and were related to the 'Northern Flint' race. Some differences among these cultivars were detected. 'Norteno Largo' was closely related to Northern Flint, while Basto/Enano Levantino was different from the rest of the cultivars. It was concluded that the development of hybrids combining good yield and the typical agronomic characteristics of flint maize is feasible., IT IS WELL KNOWN that the heterotic pattern Reid x Lancaster is the most common scheme used by commercial companies to produce hybrids for the temperate areas of the world. [...]

In Mediterranean countries, the principal corn (Zea mays L.) pest is the pink stem borer (PSB) (Sesamia nonagrioides Lef.), followed in importance by the European corn borer (ECB) [Ostrinia nubilalis (Hubner)]. Our objective was to quantify injury by these pests in a set of inbreds that showed different levels of ear damage by the PSB in a previous study and in their hybrids. A diallel among seven sweet corn inbreds that varied for ear damage by PSB was evaluated in three environments under PSB and ECB infestations. The importance of general combining ability (GCA) and specific combining ability (SCA) for ear damage by corn borer was determined. Inbred parents were also tested under manual infestation conditions with both borers. There was variability for ear damage traits among sweet corn inbred lines, but none of them were completely resistant. General combining ability effects were significant for the general appearance of the ear, ears with damaged grain, and ears with damaged shanks under PSB infestation. Under PSB infestation, SCA was not significant for any trait. Most traits showed significant GCA effects under ECB infestation, although SCA effects were also important for some damage traits. The inbred EP61 could supply some favorable alleles because it showed negative and significant GCA effects for ear damage under infestation by both species. Inbreds EP59 and V7726 showed negative and significant GCA effects for ear damage by ECB. These inbreds could be included in a sweet corn synthetic population that would be improved to decrease ear damage by corn borers., IN SPAIN AND OTHER MEDITERRANEAN COUNTRIES, the principal corn pests are the PSB (Anglade, 1972) and the ECB. In Mediterranean countries, the PSB is more abundant than the ECB. The [...]