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In cereals, the primary cell wall is built of a skeleton of cellulosic microfibrils embedded in a matrix of hemicelluloses and smaller amounts of pectins, glycoproteins and hydroxycinnamates. Later, during secondary wall development, p-coumaryl, coniferyl and sinapyl alcohols are copolymerized to form mixed lignins. Several of these cell wall components show a determinative role in maize resistance to pest and diseases. However, defense mechanisms are very complex and vary among the same plant species, different tissues or even the same tissue at different developmental stages. Thus, it is important to highlight that the role of the cell wall components needs to be tested in diverse genotypes and specific tissues where the feeding or attacking by the pathogen takes place. Understanding the role of cell wall constituents as defense mechanisms may allow modifications of crops to withstand pests and diseases. ; Studies by the authors' group were supported by the Plan Nacional I+D+I (AGL2003-00961, AGL2006-1314, AGL2009-09611, AGL2012-33415). Nowadays, R. Santiago acknowledges postdoctoral contract "Isidro Parga Pondal" supported by the Autonomous Government of Galicia and the European Social Fund. ; Peer reviewed

The objective of this study was to investigate the stability, across well-differentiated environments, of genetic control of maize resistance to Fusarium graminearum and Fusarium verticillioides ear rots and mycotoxin contamination, found in genotypes of diverse origin and adapted to different environments. This knowledge will help to design the most appropriate breeding programme to reduce mycotoxin content across a wide range of environments. Although maize genetics involved in resistance to ear rots and mycotoxin contamination greatly depended on the environment, additive and dominance effects were the predominant genetic effects in most environments. The stability across environments for resistance to ear rots and deoxynivalenol and fumonisin contamination was low, and recommended target areas of breeding programmes for either Fusarium species are different based on the different nature of genetic effect × environment interactions for each species. In general, the classification of inbreds and hybrids according to their resistance levels was similar across environments, suggesting that the same sources of resistance could be suitable for different environments, and breeding for resistance to one species would affect resistance to the other one. ; This research was supported by the National Plan for Research and Development of Spain (AGL2009-12770). R.S. acknowledges postdoctoral contracts 'Isidro Parga Pondal' supported by the Autonomous Government of Galicia and the European Social Fund and 'Ramón y Cajal' supported by the Ministry of Economy and Competitiveness of Spain. Funding for the Canadian part of this project was in part by an AAFC partnership with the Canadian Field Crop Research Alliance (CFCRA) though AAFC's Developing Innovative Agri-Products Initiative of the Growing Canadian Agri-Innovations Program. ; Ministerio de Economía y Competitividad (España ; Xunta de Galicia ; Agriculture and Agri-Food Canada ; Peer reviewed

This article is the copyright property of the Entomological Society of America and may not be used for any commercial or other private purpose without specific written permission of the Entomological Society of America ; Insect activity has long been associated with Fusarium infection. The objectives of the current study were 1) to estimate the impact of Mediterranean corn borer, Sesamia nonagrioides Lefèbvre, damage on fumonisin contamination in the maize kernel by comparing fumonisin contamination under infestation and protected conditions, and 2) to measure the potential use of genotypes resistant to this borer as controlling factors of fumonisin contamination. Genotypes with increased kernel damage by borers tended to increase fumonisin accumulation under infestation conditions. In particular environments, other factors influenced fumonisin contamination more than damage by borers. When ear damage by borers is significant, maize resistance to ear damage could contribute to the reduction of fumonisin contamination in the kernels. Genotype such as EP42 × EP77 that combines low ear damage by borers and low fumonisin level across environments is a good choice to control fumonisin contamination. The use of an applicable methodology to identify Mediterranean corn borer-resistant genotypes to ear attack under artificial infestations might be a promising approach. © 2013 Entomological Society of America. ; National Plan for Research and Development of Spain ; Autonomous Government of Galicia ; JAE Program of the Spanish Council of Research ; European Social Fund ; This research was supported by the National Plan for Research and Development of Spain (AGL2006-13140, AGL2009-09611) and the Autonomous Government of Galicia(PGIDIT06TAL40301PR). A. Cao acknowledges funding from the JAE Program of the Spanish Council of Research. R. Santiago acknowledges postdoctoral contract "Isidro Parga Pondal" supported by the Autonomous Government of Galicia and the European Social Fund. ; Peer Reviewed

Abstract Background To elucidate the role of the length of the internode basal ring (LIBR) in resistance to the Mediterranean corn borer (MCB), we carried out a divergent selection program to modify the LIBR using two maize synthetic varieties (EPS20 and EPS21), each with a different genetic background. We investigated the biochemical mechanisms underlying the relationship between the LIBR and borer resistance. Selection to lengthen or shorten the LIBR was achieved for each synthetic variety. The resulting plants were analyzed to determine their LIBR response, growth, yield, and borer resistance. Results In the synthetic variety EPS20 (Reid germplasm), reduction of the LIBR improved resistance against the MCB. The LIBR selection was also effective in the synthetic variety EPS21 (non-Reid germplasm), although there was no relationship detected between the LIBR and MCB resistance. The LIBR did not show correlations with agronomic traits such as plant height and yield. Compared with upper sections, the internode basal ring area contained lower concentrations of cell wall components such as acid detergent fiber (ADF), acid detergent lignin (ADL), and diferulates. In addition, some residual 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3-(4H)-one (DIMBOA), a natural antibiotic compound, was detected in the basal area at 30 days after silking. Conclusion We analyzed maize selections to determine whether the basal area of maize internodes is involved in borer resistance. The structural reinforcement of the cell walls was the most significant trait in the relationship between the LIBR and borer resistance. Lower contents of ADF and ADL in the rind of the basal section facilitated the entry of larvae in this area in both synthetic varieties, while lower concentrations of diferulates in the pith basal section of EPS20 facilitated larval feeding inside the stem. The higher concentrations of DIMBOA may have contributed to the lack of correlation between the LIBR and borer resistance in EPS21. This novel trait could be useful in maize breeding programs to improve borer resistance. ; This research was supported by the National Plan for Research and Development of Spain (Projects Cod. AGL2006-13140, AGL 2009-09611). R. Santiago acknowledges postdoctoral contracts "Juan de la Cierva" partially financed by the European Social Fund and "Isidro Parga Pondal" financed by the Autonomous Government of Galicia and the European Social Fund. ; Peer Reviewed

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 XUGA40301B95 ; Xunta de Galicia ; No

Fusarium graminearum Schwabe is one of the predominant fungal species responsible for stalk rot of maize in Canada and many other countries. Adapted sources of resistance to this disease are scarce but recently a few have been identified. To evaluate the usefulness of these sources in a breeding programme to improve stalk rot resistance, a complete diallel cross of five inbreds of varying susceptibility to stalk rot was conducted. Artificial inoculations of stalks were accomplished by injecting a conidial suspension into the first internode above the uppermost aerial root node. Stalk rot ratings, yield and lodging in the parents, crosses and reciprocals were evaluated over two field seasons. There were significant differences between inbred lines and hybrids for stalk rot ratings. Inbreds CM174 and CO325 were highly susceptible, whereas inbreds 73405 and 73353 were classified as resistant and both had good general combining ability. Those inbreds could be used as donors of favourable alleles in breeding programmes for Gibberella stalk rot resistance. © 2009 Consejo Superior de Investigaciones Cientificas (CSIC). ; Autonomous Government of Galicia (Spain) ; Peer Reviewed

Breeding maize (Zea mays L.) for traditional agriculture can increase quality and added value of agricultural products and allow the recovery of traditional foods. The objectives of this work were to evaluate improved open-pollinated populations under organic and conventional agriculture in order to determine the effects of selection for yield and flour yield and the relationship between agronomic and quality traits under both cropping systems. We have selected open-pollinated maize populations for flour yield and bakery quality under organic conditions, improved them under conventional conditions and evaluated the breeding programs under organic and conventional conditions. Breeding was efficient for grain and flour yield under organic agriculture for Meiro (an open-pollinated population with black grains) but not for the other populations neither in organic nor in conventional conditions. Yield ranks of varieties were moderately correlated under both conditions, and genotype × environment interaction (GE) was significant for most traits when the analyses of variance were made over all environments but also when organic and conventional environments were separated. GE was higher under organic agriculture. Correlations between traits were higher under conventional agriculture and there were important discrepancies between correlations in organic and conventional agriculture. We concluded that selection under conventional agriculture was efficient for one population under organic agriculture. Selection under the target environment could increase the possibilities of success. ; Research was supported by the Spanish Plan for Research and Development (project code AGL2010-22254), the Basque Government, and the Diputación Provincial de Pontevedra. ; Peer Reviewed

Genetic improvement is an effective and environmentally safe method to reduce the levels of fumonisin mycotoxins in corn kernels infected with Fusarium verticillioides. In order to find new sources of resistance, a wide collection of corn inbred lines were evaluated for Fusarium ear rot and fumonisin accumulation after inoculation of the kernels with Fusarium verticillioides. Augmented designs were used for testing 240 un-replicated inbreds and 6 inbred checks in 2010 and 2011. Sixty-one inbreds were found to have the highest levels of resistance to Fusarium ear rot and fumonisin accumulation across years. Inbreds differing in kernel color, use, kernel type and heterotic group were all represented in this group of 61 inbreds. White corn inbreds had higher levels of fumonisin than yellow corn inbreds, but it was still possible to find white inbreds with comparable resistance to fumonisin accumulation to that of the most resistant yellow inbreds. Similarly, although the sweet corn inbreds evaluated in this study were less resistant to infection by F. verticillioides than the field corn inbreds, there were some which were grouped in the most resistant 61 inbreds. Many of these inbreds can be used to improve resistance to F. verticillioides infection and fumonisin accumulation by crossing the most resistant inbreds of each subgroup. ; MICINN ; Spanish Council of Research. ; Autonomous Government of Galicia ; European Social Fund ; This research was supported by the National Plan for Research and Development of Spain (AGL2009-12770). A. Cao acknowledges funding from the JAE Program of the Spanish Council of Research. R. Santiago acknowledges postdoctoral contract "Isidro Parga Pondal" supported by the Autonomous Government of Galicia and the European Social Fund. ; 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

[Background] Plant breeding has been proposed as one of the most effective and environmentally safe methods to control fungal infection and to reduce fumonisin accumulation. However, conventional breeding can be hampered by the complex genetic architecture of resistance to fumonisin accumulation and marker-assisted selection is proposed as an efficient alternative. In the current study, GWAS has been performed for the first time for detecting high-resolution QTL for resistance to fumonisin accumulation in maize kernels complementing published GWAS results for Fusarium ear rot. ; [Results] Thirty-nine SNPs significantly associated with resistance to fumonisin accumulation in maize kernels were found and clustered into 17 QTL. Novel QTLs for fumonisin content would be at bins 3.02, 5.02, 7.05 and 8.07. Genes with annotated functions probably implicated in resistance to pathogens based on previous studies have been highlighted. ; [Conclusions] Breeding approaches to fix favorable functional variants for genes implicated in maize immune response signaling may be especially useful to reduce kernel contamination with fumonisins without significantly interfering in mycelia development and growth and, consequently, in the beneficial endophytic behavior of Fusarium verticillioides. ; This research was funded by the Autonomous Government of Galicia, Spain (project IN607A/013), and by the "Secretaría de Estado de Investigación, Desarrollo e Innovación", Spain, within the projects AGL2015–67313-C2–1-R and AGL2015–67313-C2–2-R, which were co-financed with European Social Funds. R. Santiago acknowledges postdoctoral contract "Ramón y Cajal" financed by the "Secretaría de Estado de Investigación, Desarrollo e Innovación" and co-financed by the "Universidad de Vigo", Spain, and the European Social Funds.

8 páginas, 6 figuras y 1 tabla. ; Alternative approaches to linkage and association mapping using inbred panels may allow further insights into loci involved in resistance to Fusarium ear rot and lead to the discovery of suitable markers for breeding programs. Here, the suitability of a maize multiparent advanced generation intercross population for detecting quantitative trait loci (QTLs) associated with Fusarium ear rot resistance was evaluated and found to be valuable in uncovering genomic regions containing resistance-associated loci in temperate materials. In total, 13 putative minor QTLs were located over all of the chromosomes, except chromosome 5, and frequencies of favorable alleles for resistance to Fusarium ear rot were, in general, high. These findings corroborated the quantitative characteristic of resistance to Fusarium ear rot in which many loci have small additive effects. Present and previous results indicate that crucial regions such as 210 to 220 Mb in chromosome 3 and 166 to 173 Mb in chromosome 7 (B73-RefGen-v2) contain QTLs for Fusarium ear rot resistance and fumonisin content. ; This research was funded by the "Plan Estatal de Ciencia y Tecnologia de España" within the projects AGL2015-67313-C2-1-R and AGL2015-67313-C2-2-R, which were co-financed with European Union funds under the FEDER program, and the project IN607A/013 funded by the Autonomous Government of Galicia, Spain. R. Santiago acknowledges postdoctoral contract "Ramón y Cajal" financed by the Ministry of Economy and Competiveness (Spain), Vigo University, and the European Social Fund. ; Peer reviewed

1 página-. Resumen del póster presentado en el Seminario celebrado en Tullm, Austria, entre el 8 y el 11 de abril de 2018. ; In current study, GWAS has been performed for the first time for detecting high-resolution QTL for resistance to fumonisin accumulation in maize kernel. A subset of 270 inbred lines from a maize diversity panel (composed of 302 inbred lines) that represents much of the diversity available in public breeding sector around the world was evaluated under inoculation with Fusarium verticillioides. Significant associations between polymorphisms at SNPs in bins 1.07, 1.09, 2.08, 3.02, 3.04, 3.05, 3.06, 3.08, 3.09, 4.02, 4.05, 5.02, 6.07, 7.05, 8.07, 9.03 and fumonisin accumulation (determined by ELISA tests) in maize kernel were detected. At least, four associations should be behind novel QTL because QTL were not found in that bin or in adjacent bins in previous studies (Robertson-Hoyt et al. 2006; Maschietto et al. 2017). These novel QTLs for fumonisin content would be at bins 3.02, 5.02, 7.05, and 8.03. Genes likely involved in ROS production, ROS-scavenging and ROS-detoxification, in signaling and/or regulation of plant hormone-mediated responses and lipid metabolism were proposed as candidate genes behind significant associations. ; This research was funded by the "Plan Estatal de Ciencia y Tecnologia de España" (project AGL2015-67313-C2-1-R, co-financed with European Union funds under the FEDER program) and by Autonomous Government of Galicia, Spain (projects IN607A/013 and ED431F 2016/014). ; Peer reviewed

The theoretical utility of two alternative methods, random (r) and convergent (c) cross methods, of producing maize synthetics has previously been ascertained in two different genetic backgrounds (EPS20 derived from eight Reid inbred lines with origin from the US Corn Belt population "Reid", and EPS21 formed from eight non-Reid inbreds). However, the agronomical consequences of using one or another methodology have not been tested. The objectives of the present study were to determine, in two genetic backgrounds, whether synthetics developed by the random and convergent cross methods differed in agronomic performance and to investigate whether some allelic changes previously observed by Butrón et al. [Butrón, A., Tarrío, R., Revilla, P., Malvar, R.A., Ordás, A., 2003. Molecular evaluation of two methods for developing maize synthetic varieties. Mol. Breed. 12, 329–333.] could be directly implicated in those differences. The synthetics and the diallel crosses among them, testcrosses of EPS20c and EPS20r to their Reid parental inbreds and testcrosses of EPS21c and EPS21r to their non-Reid parental inbreds were evaluated for grain yield in three trials in 2004 and 2005. Our results suggest that directional selection for germination, which occurs during the process of formation of synthetics using the random method (but absent with the convergent cross method) was responsible for agronomic and genetic differences between synthetics obtained by alternative methods from the same set of inbreds. Although selection for germination increased the yield performance of the synthetic obtained from the Reid inbreds, in a more heterogeneous genetic background, natural selection against non-competitive inbred lines at germination would be responsible for an important reduction of variability that would reduce yield. ; Research supported by the Ministry of Science and Education of Spain (AGL2004-06776), the Autonomous Government of Galicia (Xunta-PGDIT05PXIC40301PN), and the Excma. Deputación Provincial of Pontevedra, Spain. MC Romay acknowledges a fellowship from the Ministry of Science and Education of Spain. ; MEC ; Xunta de Galicia ; Diputación Provincial de Pontevedra ; Peer reviewed

B73 and Mo17 represent the main families of elite maize (Zea mays L.) inbred lines. B73 and Mo17 significantly differed in their proportion of germination under low-temperature conditions, and the IBM population derived from the cross B73 x Mo17 provides breeders a great opportunity for locating quantitative trait loci (QTLs) for cold tolerance in elite maize germplasm, the objective of this study. Under low-temperature conditions, the recombinant inbred lines significantly differed for all traits except vigor. No QTLs were detected at optimal conditions, but two QTLs involved in leaf color at low temperature were located in the short arm of chromosome 3 and the long arm of chromosome 6. The final fit for QTLs detected in our study explained 14.2% of phenotypic variance and 28.2% of genetic variance. However, in cross-validation analysis, QTLs detected in chromosomes 3 and 6 were detected in only 12.3% and 25.7% of all cross-validation runs, respectively, and explained 3.7% of the genetic variance. Although Mo17 could bring some favorable alleles, marker-assisted selection is not advisable because differences between allelic variants are small and explain a low proportion of genotypic variance. The locus luteus11 is proposed as a candidate gene for the QTL located in chromosome 6, while the QTL located in chromosome 3 probably corresponds to an unknown gene. ; We thank the Maize Genetic Cooperation Stock Center for germplasm and the Maize Genetics and Genomics Database for genotyping data. Research was supported by the National Plan for Research and Development AGL2004-06776), the Autonomous Government of Galicia (PGIDIT04RAG403006PR), and the Excelentísima Diputación Provincial de Pontevedra. V. M. Rodríguez acknowledges his fellowship from the Ministry of Science and Technology from Spain. ; MCYT ; Diputación de Pontevedra ; Peer reviewed