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Plant long-term response against chewing insects could become stronger than initial reactions and even turn into systemic. The objectives of the present study were 1) to evaluate whether the long-running attack to the stem by corn borers can improve the stem antibiotic properties; 2) to check whether hydroxycinnamic acids could be involved in this antibiotic response; 3) and to check whether elicitation by Sesamia nonagrioides Lef. (Lepidoptera: Noctuidae) regurgitant could activate long-term plant responses. In this sense, we observed that long-term feeding by S. nonagrioides larvae induced genotype-dependent changes in stem antibiosis and phenolic profiles, but the hydroxycinnamate content does not have a significant role in the systemic defense induced by the attack. In addition, response to long-term feeding by larvae could not be fully mimicked by elicitation using S. nonagrioides regurgitant alone. For the first time, it has been demonstrated that 'long-term' attack to the stem by corn borers can increase the stem antibiotic properties, and this has to be considered attending to breeding strategies.

Limited attention has been paid to maize (Zea mays L.) resistance induced by corn borer damage, although evidence shows that induced defenses have lower resource allocation costs than constitutive defenses. Maize responses to short- and long-term feeding by the Mediterranean corn borer (MCB, Sesamia nionagrioides) have been previously studied, but the suggested differences between responses could be due to experimental differences. Therefore, in the current study, a direct comparison between short- and long-term responses has been made. The objectives were (i) to determine changes in the level of antibiosis of the stems induced by feeding of S. nonagrioides larvae for 2days (short-term feeding) and 9days (long-term feeding), (ii) to characterize the metabolome of the stems’ short- and long-term responses to borer feeding, and (iii) to look for metabolic pathways that could modulate plant resistance to MCB. Defenses were progressively induced in the resistant inbred, and constitutive defenses were broken down in the susceptible inbred. Results suggest that the different resistance levels of the two inbreds to stem tunneling by MCB could depend on their ability to establish a systemic response. Based on these results, a high throughput look for specific metabolites implicated in systemic induced resistance to maize stem borers is recommended; the current focus on constitutive defense metabolites has not been successful in finding molecules that would be valuable tools for pest control. Agencia Estatal de Investigación | Ref. RTI2018-096776-B-C21 Agencia Estatal de Investigación | Ref. RTI2018-096776-B-C22

The cell wall putatively plays a role in host-plant resistance to phytopathogens. Here, we investigated which cell wall-bound phenolic compounds have determining roles in maize (Zea mays) resistance to attack by the Mediterranean corn borer Sesamia nonagrioides (Lefebvre). Diverse sets of maize genotypes having contrasting hydroxycinnamate contents and borer resistance levels were evaluated. The interdependent relationships among some cell wall-bound phenolic compounds, such as ferulic acid and its dimers, or p-coumaric acid and syringyl lignin subunits, were analyzed. Both p-coumaric acid and syringyl momoners showed significant negative correlations with damage, as assessed by tunnel lengths, caused by S. nonagrioides larvae. Thus, the use of cell wall-bound p-coumaric acid in pest-resistant crop breeding programs is advisable.

4 páginas y 3 tablas, Two decades of investigations on maize resistance to Mediterranean corn borer (Sesamia nonagrioides Lefebvre; MCB) have shown that breeding for increased resistance to stem tunnelling by MCB often resulted in reduced yield because significant genetic correlation between both traits exists in some backgrounds. Unlike phenotypic selection, marker-assisted selection (MAS) could differentiate markers linked only to one trait from those linked simultaneously to yield potential and susceptibility to the pest. In the current study, the suitability of MAS for improving resistance to stem tunnelling without adverse effects on yield has been tested. The unfavourable genetic relationship between yield potential and susceptibility could be overcome using MAS. Gains obtained using MAS were weak, because genetic variance explained by the quantitative trait loci (QTL) was low but results encourage us to persevere in using marker information for simultaneous improvement of resistance and yield especially if genome-wide approaches are applied. Approaches to detect QTL are widely used, but studies on the suitability of markers linked to QTL for performing MAS have been mostly neglected., This research was supported by the National Plan for Research and Development of Spain (AGL2015-67313-C2-1-R), and co-financed by the European Social Fund

11 páginas, 4 figuras y 3 tablas., Plants defend themselves against herbivores by activating a plethora of genetic and biochemical mechanisms aimed at reducing plant damage and insect survival. The short-term plant response to insect attack is well understood, but less is known about the maintenance of this response over time. We performed transcriptomic and metabolomics analyses in order to identify genes and metabolites involved in the long-term response of maize to attack by the corn borer Sesamina nonagrioides. To determine the role of elicitors present in caterpillar secretions, we also evaluated the response of maize stem challenged with insect regurgitates. The integrative analysis of the omics results revealed that the long-term response in maize is characterized by repression of the primary metabolism and a strong redox response, mainly mediated by germin-like proteins to produce anti-nutritive and toxic compounds that reduce insect viability, and with the glutathione–ascorbate cycle being crucial to minimize the adverse effects of reactive oxygen species (ROS) on the plant. Our results suggest that different defense mechanisms are involved in the long-term response compared to those reported during the early response. We also observed a marginal effect of the caterpillar regurgitates on the long-term defensive response., This research was funded by the “Plan Estatal de Ciencia y Tecnologia de España” within the projects AGL2012-33415 and AGL2015-67313-C2-1-R, both of which were co-financed by European Union funds under the FEDER program, and the project: IN607A/013 funded by the Autonomous Government of Galicia, Spain. RS acknowledges the “Ramón y Cajal” postdoctoral contract financed by the Ministry of Economy and Competiveness (Spain), Vigo University, and the European Social Fund.

[Background] Sesamia nonagrioides Lefebvere (Mediterranean corn borer, MCB) is the main pest of maize in the Mediterranean area. QTL for MCB stalk tunneling and grain yield under high MCB infestation had been located at bin 8.03–8.05 (4–21 cM and 10–30 cM respectively) in a previous analysis of the EP42 x EP39 RILs mapping population. The objective of the present work was to study with higher resolution those QTL, and validating and estimating with higher precision their locations and effects. To achieve this objective, we developed a set of 38 heterogeneous inbred families (HIFs) which were near-homozygous in the genome, except in the region under study. The HIFs were evaluated in multiple environments under artificial infestation with MCB and genotyped with SNPs., [Results] The QTL for grain yield under high infestation was confirmed with higher precision and improved reliability at 112.6–116.9 Mb. On the contrary, the location of the QTL for stalk tunneling was not validated probably due to the fixation of some genomic regions during the development of the HIFs. Our study confirmed that the co-localization of the QTL for stalk tunneling and grain yield in the previous study was due to linked genes, not to pleiotropic effects. So, the QTL for grain yield can be used for improving grain yield without undesirable effect on stalk tunneling., [Conclusions] The HIF analysis is useful for validating QTL and for conducting deeper studies in traits related to corn borer resistance., This research was funded by the Plan Estatal de Ciencia y Tecnologia de España within the projects AGL2012–33415 and AGL2015–67313-C2–1-R, both of which were co-financed with European Union funds under the FEDER program.

[Background] Plants can respond to insect attack via defense mechanisms that reduce insect performance. In this study, we examined the effects of several treatments applied to two maize genotypes (one resistant, one susceptible) on the subsequent growth and survival of Sesamia nonagrioides Lef. (Mediterranean corn borer, MCB) larvae. The treatments were infestation with MCB larvae, application of MCB regurgitant upon wounding, wounding alone, or exposure to methyl jasmonate, and they were applied at the V6–V8 stage of maize development. We also monitored changes in the concentrations of compounds known to be involved in constitutive resistance, such as cell wall-bound hydroxycinnamates and benzoxazinoids., [Results] In both maize genotypes, the leaves of plants pre-infested with MCB larvae were less suitable for larval development than those from untreated plants. Application of MCB regurgitant upon wounding, and wounding itself, resulted in leaf tissues becoming less suitable for larval growth than those of pre-infested plants, suggesting that there could be herbivore-associated effector molecules that suppress some wounding responses. A single application of MCB regurgitant did not seem to mimic feeding by MCB larvae, although the results suggested that regurgitant deposited during feeding may have enhanced ferulates and diferulates synthesis in infested vs. control plants. Jasmonic acid may play a role in mediating the maize response to MCB attack, but it did not trigger hydroxycinnamate accumulation in the leaves to a level comparable to that induced by larval leaf feeding. The EP39 maize genotype showed an increase in leaf cell wall strength by increasing hemicellulose cross-linking in response to MCB attack, while induced defenses in the EP42 plants appeared to reflect a broader array of resistance mechanisms., [Conclusions] The results indicated that leaf feeding by MCB larvae can increase leaf antibiosis against MCB in two maize genotypes with contrasting levels of resistance against this borer. Also, the larval regurgitant played a positive role in eliciting a defense response. We determined the effects of the plant response on larval growth, and detected defense compounds related to borer resistance., This research was supported by the National Plan for Research and Development of Spain (AGL2012-33415, AGL2015-67313-C2-1-R, and AGL2015-67313-C2-2-R) co-financed by the European Social Fund (FEDER). R. Santiago acknowledges postdoctoral contract “Ramón y Cajal” financed by the Ministry of Economy and Competitiveness (Spain), Vigo University, and the European Social Fund.

21 Pag., 2 Tabl. The definitive version is available at www.springerlink.com, Mediterranean corn borer (MCB) (Sesamia nonagrioides Lef) and European corn borer (ECB) (Ostrinia nubilalis Hbn) are the most important biotic stresses of maize in Europe. The first selection program to improve stalk resistance to MCB was carried out in the maize population EPS12. It has shown that selection was effective to improve stalk resistance to MCB and ECB, while yield was not significantly diminished. The objective of this research was to determine if correlated changes in EPS12 occurred due to selection for resistance to MCB. Cycles of selection per se and testcrosses to three testers were evaluated under MCB and ECB artificial infestation at two different Spanish locations during 2 years. Selection has significantly reduced cob damage, days to silking, plant and ear height, and 100-kernel weight; meanwhile early vigor was increased. These changes could rather be a consequence of unconscious selection and/or the genetic correlation of these traits with resistance than a consequence of genetic drift., Research supported by the Plan Nacional I+D+I (AGL2003-00961 and AGL2006-1314). G. Sandoya acknowledges a fellowship from the Ministry of the Education and Science that allowed him to carry out this study; part of this study is a thesis by the senior author for the Ph.D. degree.

Recurrent selection has been reported as successful for improving maize resistance against corn borers. This study was conducted to determine if phenolics concentration in maize changes during recurrent selection to improve stalk resistance to the Mediterranean corn borer. Three cycles of selection [EPS12(S)C0, ESP12(S)C2, and EPS12(S)C3] from the maize synthetic population EPS12 and test crosses to inbred lines A639, B93, and EP42 were field grown and artificially infested with Mediterranean corn borer larvae, and the pith tissues were sampled for biochemical analyses. Two major simple phenolic acids [p-coumaric (p-CA) and trans-ferulic (E-FA) acids] were identified in free and cell-wall fractions, whereas four isomers of diferulic acid (DFA) (8−5′l, 5−5′, 8−o−4′, and 8−5′ benzofuran form) were present in the cell-wall bound fraction. The selection cycles EPS12(S)C0 and EPS12(S)C3 showed less damage and higher cell wall phenolics concentrations than the cycle EPS12(S)C2. In addition, higher concentrations of total DFAs were associated with shorter tunnel length and lower numbers of larvae per stem. The current study shows new and concrete evidence that the cell-wall bound phenolics could have a determinative role in the resistance to the Mediterranean corn borer, although future development of recurrent and divergent selection cycles will clarify this point.

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.

[Background] A QTL mapping study for maize resistance to the Mediterranean corn borer (MCB) was performed with a RIL population derived from the cross B73 × CML103. To develop commercial inbreds of maize resistant to the MCB for use in Europe, it would be useful to transfer resistance from tropical germplasm like the subtropical inbred CML103 to temperate lines. The inbred B73 was chosen as representative of the Stiff Stock heterotic group, a major heterotic group used in hybrid grown in both North American and Europe. The objectives were to study the architecture of genetic factors for resistance to MCB and to check the feasibility of using marker-assisted selection (MAS) for transferring those genetic factors., [Results] Eight quantitative trait loci (QTL) were declared significant for resistance traits and eight QTL were located for agronomic traits. Alleles from CML103 at QTL significant for tunnel length could reduce tunnel length made for MCB in inbred B73 in more than 8 cm; favorable alleles for yield were also found in CML103 and no genetic correlation coefficient between tunnel length and yield was detected., [Conclusions] MAS for transferring resistance genes to corn borer attack from CML103 to B73 could be successful based on cross validation results and a negative effect on yield would not be expected., This work was supported by the National Plan for Research and Development of Spain (projects AGL2009-09611 and AGL2012-33415, both funded by the European Regional Development Fund). L.F. Samayoa acknowledges a contract JAE-Predoc from the Spanish Council for Scientific Research (CSIC). MDM acknowledges research support by USDA-ARS.

The pink stem borer (Sesamia nonagrioides Lef.) is the main corn (Zea mays L.) pest in the Mediterranean area. Although, screening for resistance to this pest has been successful, the level of resistance shown by the most resistant varieties is not high. The objectives of the present work were: (i) the evaluation for pink stem borer resistance of the nontested inbred lines, field and popcorn materials, from the collection maintained at the Mision Biologica de Galicia and (ii) the study of the performance, under pink stem borer infestation, of inbreds selected for resistance to pink stem borer in hybrid combination. Forty four inbred lines nontested yet for resistant to pink stem borer along with five inbred lines previously reported as resistant to stem and ear attack, were evaluated in 2002 and 2003. In adjacent experiments, hybrids EP79× W552, EP77× B93, and A661× EP42 were tested along with a resistant hybrid, MEB531-Bt, and a susceptible hybrid, INRA 260. New sources of resistance to pink stem borer have been detected among inbred lines improving the level of resistance presented by previously tested inbreds. Some of these lines were successfully developed by pedigree selection for resistance to pink stem borer.

The pink stem borer (Sesamia nonagrioides Lefèvbre) is the most important pest of maize (Zea mays L.) throughout the Mediterranean area. The maize composite EPS12 has been chosen as the base population for a breeding program based on its resistance to pink stem borer, with the main selection criterion being resistance to stem tunneling. Yield was taken as a secondary selection criterion to avoid any unwanted negatively correlated response on this character. The aims of investigation were: (1) to monitor the effects of selection for resistance to pink stem borer on allele frequency at 70 simple sequence repeat (SSR) markers and their impact on the genetic structure of EPS12 and (2) to identify loci at which allelic frequencies changed significantly due to directional selection. Genetic diversity was reduced during the selection process (as expected since random genetic drift as well as selection could reduce genetic variability), but not significantly so. Although the loss of genetic variation was generally consistent with that expected in a model in which random genetic drift acts alone on neutral alleles, the changes observed in the frequency of five alleles were significantly greater than expected. Further, the linear trend of the departure from the random genetic drift model was significant for some allelic versions of two SSR markers, umc1329 and phi076; directional selection was therefore acting on these loci. The significant effect of directional selection on those markers suggests the presence of quantitative trait loci (QTLs) for tunnel length and/or for yield under artificial infestation with Sesamia nonagrioides on the long arm of chromosome 4., This research supported by the National Plan of Research and Development of Spain (AGL2003-0961). R. Tarrío received support from contract DoctorI3P from the National Plan of Research and Development of Spain. This study was possible thanks to the invaluable laboratory work of Ana Carballeda, Begoña Giménez, and Elisa Santiago., MCYT

Thirteen inbred lines of maize (Zea mays L.) with different levels of stem resistance to the stem borer Sesamia nonagrioides Lefevbre were evaluated in the field and the laboratory to determine the antibiotic resistance to this pest. Inbreds CM151, CO125, and EP39 had antibiotic pith as well as stem resistance, so the pith could play a role in stem resistance. Inbreds A509, F473, and PB130 did not have antibiotic pith but had stem resistance; therefore, other mechanisms could confer stem resistance. Finally, the inbred MS1334 had antibiotic pith and did not show stem resistance; thus, other factors could compensate the effect of the pith. Therefore, although pith antibiotic compound seems to play a role in the defense against S. nonagrioides attack, it is not the only possible mechanism of defense.

Length of the internode basal ring (LIBR) in maize is a morphological character that has been associated with resistance to Mediterranean corn borer (MCB), Sesamia nonagrioides Lef. The present study is the first research to evaluate the usefulness of this trait in breeding programmes. Six maize hybrids, from a complete diallel set of four inbred lines (two resistant and two susceptible to MCB), were evaluated under early and late sowing conditions at three locations in northwestern Spain. General and specific combining ability (GCA and SCA, respectively) for LIBR were estimated, and LIBR correlations with grain yield and other important agronomic traits were evaluated. Hybrid by environment interactions were not significant for LIBR and the sums of squares partitioning indicated a greater GCA effect (95%), suggesting that this trait is stable and shows important additive effects for this set of hybrids. Correlation coefficients not only indicate that selection for increasing LIBR could enhance grain yield and other related plant traits (height and silking) but also an increase in the MCB susceptibility. Based on the limited number genotypes evaluated, LIBR could be modified by selection; however, if LIBR is used as an indirect selection criterion to improve MCB resistance, then some negative effects on yield may be expected. © 2010 Blackwell Verlag GmbH.

Sesamia nonagrioides Lefebvre is a major insect pest of maize (Zea mays L.) in northwestern Spain. The inheritance of ear resistance in field corn to this pest has not been studied. This work aims to determine the importance of genetic (additive, dominance, and epistatic effects) and environmental effects in the inheritance of ear resistance to S. nonagrioides. Three field corn inbreds (CM109, EP31, and EP42) were used as parents and two crosses (CM109 × EP31 and CM109 × EP42) were made. These inbreds show different ear resistance levels to S. nonagrioides, with CM109 more resistant than EP31 and EP42. For each cross, parents (P1, P2), F1, F2, and backcrosses to each parent (BC1 and BC2) were evaluated. Correlations among ear damage traits showed that general appearance of the ear should be useful indicator of ear resistance. Ear resistance was dominant to susceptibility and was transmitted from inbreds to their hybrids. The additive-dominance model fit the generation mean analysis for both cross...

Pink stem borer (Sesamia nonagrioides Lef.) is one of the most important insect pests of corn (Zea mays L.) in southern Europe. The objectives of this work were to determine the level of resistance in different sweet corn inbreds and to identify sources of resistance to ear feeding by the pink stem borer. Twenty-eight sweet corn (su(1) and su(1)se(1)) inbreds and four resistant field corn (Su(1)Se(1)) inbreds were evaluated for ear resistance at different sowing dates, under two methods of artificial infestation. There were significant differences between infestation methods for ears with damaged grain, husks, cobs, and shanks. The inbred×infestation method interaction was significant for general appearance of the ear. The most resistant inbreds were identified by using mean comparisons and principal component analysis of ear damage traits. All inbreds were damaged. Hence, resistance was incomplete and in need of improvement. EP59, H3, I5125, IL767b, and V7726 were the most resistant sweet corn inbreds, which did not differ significantly from A635, the most resistant field corn inbred. General appearance of the ear appears to be a good indicator of pink stem borer resistance and can be used in preliminary evaluation. Variability exists in the resistance of these sweet inbreds to the pink stem borer and the use of field corn inbreds may not be necessary in the improvement of resistance, although further research is needed to determine if the sources differ in the pertinent genes conferring resistance.

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.

6 pags., 4 tabls. The definitive version is available at: http://www.bioone.org/doi/full/10.1603/EC12013, In the Mediterranean area, the main corn borer species are Sesamia nonagrioides Lefebvre (Mediterranean corn borer) and Ostrinia nubilalis Hübner (European corn borer). In the overall context of integrated pest control, it is possible to reduce the effect of a pest without having a negative effect on the environment by varying the sowing date. Benefits are possible if the most susceptible stages of the crop no longer coincide with the peak of the pest. We used different cycles of selection (0, 6, 8, 10, and 12) of two populations (Purdue A and Purdue B) of maize selected for early flowering to get a more precise estimation of the relationship between maturity of plant tissues and corn borer damage. We found a relationship between the damage produced by corn borers and the number of days from flowering to infestation. We conclude that, after flowering, a later stage of plant development at the moment of the infestation by corn borers reduces the damage caused by the larvae. Based on our results, we recommend to plant as early as possible so the tissues would be as mature as possible at the moment of insect attack., This research was supported by the National Plan for Research and Development of Spain (Project Cod. AGL2006-13140) B. Ordas acknowledge a contract from the Xunta de Galicia (Isidro Parga Pondal program)

In spite of multiple studies elucidating individual defense mechanisms against stalk borer feeding, little information is available about the plant response to these members of Lepidoptera. Four maize inbred lines were cultivated in a greenhouse and challenged with larvae of the corn borer Sesamia nonagrioides. Transcriptome and biochemical analyses were performed to elucidate the maize response mechanisms to this insect. General plant defense mechanisms were activated, including the jasmonic acid biosynthetic pathway, proteinase inhibitors, and four defenserelated transcription factors. Interestingly, gene ontology analysis shows that maize plants undergo cell-wall reorganization after being attacked. These results were confirmed through biochemical analyses showing that the concentration of some cell-wall-related compounds significantly changed after plant infestation in a genotype-dependent way. In conclusion, maize plants respond to the attack of the corn borer S. nonagrioides through cell-wall fortification, activating genes involved in cell-wall organization, which finally is reflected in a higher concentration of some cell-wall components, especially in resistant genotypes., This work by supported by the Spanish National Plan for Research and Development (grant nº AGL2009-09611).

31 Pag., 3 Tabl., 1 Fig. The definitive version is available at: http://www3.interscience.wiley.com, A maize synthetic population was improved for resistance to the Mediterranean corn borer (MCB, Sesamia nonagrioides) while maintaining yield. The objectives of this research were to investigate whether yield and yield stability of the maize synthetic population named EPS12 were affected by selection for MCB resistance; also to determine which genotypic and environmental covariates could explain the genotype (G), environment (E) and genotype × environment (GE) effects for yield under corn borer infestation. Plants from three cycles of selection and their testcrosses to three inbred testers (A639, B93 and EP42) were evaluated at two locations in 2 years, under MCB and European corn borer infestations. After selection EPS12 was a more stable genotype. Hybrids derived from crosses between B93 and inbreds obtained from the initial cycles of selection could be recommended for cultivation in northern Spain. The yield of crosses between cycles of selection and testers increased when there were fewer days with temperatures >25°C and higher mean maximum temperatures. Differences in yield among these genotypes were mostly explained by resistance to corn borer attack. In general, among EPS12-derived materials, genetic characteristics that contribute to increased grain yield were also responsible for increased abiotic stress tolerance., G. Sandoya acknowledges three consecutive grants from: C. Iturriaga and Maria de Dañobeitia Foundation, the Mediterranean Agronomic Institute of Zaragoza (CIHEAM), and the Ministry of Education and Science (Spain).

39 pages, 1 figure, 3 tables.-- Provisional PDF., [Background] Ostrinia nubilalis (ECB) and Sesamia nonagrioides (MCB) are two maize stem borers which cause important losses in temperate maize production, but QTL analyses for corn borer resistance were mostly restricted to ECB resistance and maize materials genetically related (mapping populations derived from B73). Therefore, the objective of this work was to identify and characterize QTLs for MCB resistance and agronomic traits in a RILs population derived from European flint inbreds., [Results] Three QTLs were detected for stalk tunnel length at bins 1.02, 3.05 and 8.05 which explained 7.5 % of the RILs genotypic variance. The QTL at bin 3.05 was co-located to a QTL related to plant height and grain humidity and the QTL at bin 8.05 was located near a QTL related to yield., [Conclusions] Our results, when compared with results from other authors, suggest the presence of genes involved in cell wall biosynthesis or fortification with effects on resistance to different corn borer species and digestibility for dairy cattle. Particularly, we proposed five candidate genes related to cell wall characteristics which could explain the QTL for stalk tunnelling in the region 3.05. However, the small proportion of genotypic variance explained by the QTLs suggest that there are also many other genes of small effect regulating MCB resistance and we conclude that MAS seems not promising for this trait. Two QTLs detected for stalk tunnelling overlap with QTLs for agronomic traits, indicating the presence of pleitropism or linkage between genes affecting resistance and agronomic traits., This research was supported by the National Plan for Research and Development of Spain (Project Cod. AGL2006-13140). B Ordas and Rogelio Santiago acknowledge a contract from the Xunta the Galicia (Isidro Parga Pondal program) and from the Spanish Ministry for Science and Innovation (Juan de la Cierva program), respectively.

In maize, the Mediterranean corn borer (MCB), Sesamia nonagrioides Lef, is the insect pest that causes the most significant yield losses in north-western Spain. A S1 recurrent selection program to improve resistance of EPS12 against MCB was evaluated previously. In the current study two experiments were conducted to determine if antibiosis and/or structural mechanisms were responsible for the improvement in resistance in this synthetic. Larval growth or survival of MCB was not significantly affected to consider the presence of antibiotic factors in the pith. Besides, pith puncture resistance, previously reported as a possible resistance trait in single inbred lines, did not show significant differences between cycles of selection. Length of the internode basal ring (LIBR) was the structural character most related to stem resistance improvement to MCB in the current evaluation. There was a high positive correlation between MCB tunnel length and LIBR (P ≤ 0.01, R2 = 0.99). The larvae would enter the plant throughout the internode basal area and, this way, they could avoid the increased thickness or hardness of the remaining rind area. LIBR might be a useful measure in future resistance breeding programs against this borer., This research was supported by the Plan Nacional I + D + I (AGL2003-00961, AGL2006-1314, and AGL2009-0961). G. Sandoya acknowledges a fellowship from the Ministry of Education and Science that allowed him to carry out this study. R. Santiago acknowledges a postdoctoral contract “Juan de la Cierva” partially financed by the European Social Fund., MCYT, MIC, UE

Our knowledge of the genetics of resistance to the pink stem borer (Sesamia nonagrioides) in maize (Zea mays) is restricted to a few crosses among maize inbreds. The objectives of this study were to enlarge our understanding of the genetics of traits related to damage by pink stem borer and yield under infestation and to use generation means analyses to compare per se and testcross performance for detecting epistatic effects. All generations, either per se or crossed to testers, were evaluated in a 10 × 10 triple lattice design under artificial infestation with S. nonagrioides in 2005 and 2006. Most traits fit an additive–dominance model; but evidence for epistasis for resistance and yield under infestation was shown. Epistasis, in general, did not appear to play an important role in the inheritance of yield under pink stem borer infestation. However, the epistasis contribution to maize yield performance could be important in some outstanding crosses such as EP42 × A637. Testcross generation means revealed epistatic effects undetected by the generation means analysis, but neither method was able to eliminate dominance effects that could prevail over epistatic effects., Research supported by the Ministry of Science and Education of Spain (AGL2006-13140-C02-01) and the Excma. Deputación Provincial of Pontevedra, Spain. G. S. acknowledges a fellowship from the Ministry of Science and Education of Spain., MEC, Diputación Provincial de Pontevedra

In northwestern Spain, the grounded whole kernel of flint maize (Zea mays L.) landraces is traditionally used for making bread and other bakery products. We have identified some local varieties appropriate for traditional bakery. Thus far, evaluations have been made under low corn borer pressure, but to know their ability to compete for yield and quality in a wider area, evaluations should be done under higher corn borer, specifically targeting Sesamia nonagrioides (Lepidoptera: Noctuidae) and Ostrinia nubilalis (Lepidoptera: Crambidae) pressure. Therefore, the objectives of this study were to explore the stem and ear resistance to corn borer attack of maize landraces already evaluated for yield, kernel, and bread tasting qualities under organic farming conditions and to know possible relationships among yield, quality and corn borer damage traits. No significant correlation coefficients were detected between yield and quality-related traits. Therefore, simultaneous progress for yield and quality could be made. Many varieties providing high yield and kernel density under high insect pressure were similar to the ones selected by the same characteristics under low insect pressure in a previous study. However, under high insect pressure, varieties with less stem and shank damage by S. nonagrioides are recommended for reducing losses and the risk of kernel contamination with fumonisins. Among the late varieties, Bianco Perla would be the most appropriate to obtain high yield along with reduced stem damage by S. nonagrioides and reduced risk of fumonisin contamination. In areas with shorter growing season, EPS12 (T) C3 and Rebordanes would be the most suitable varieties for obtaining high-quality flours under high insect pressure., This research was supported by the National Plan for Research and Development (AGL2003-0961 and AGL2006-03140-C02-01) and the Excma Diputación Provincial de Pontevedra. G. Sandoya acknowledges his fellowship from the Ministry of Education and Science of Spain., MCYT, Diputación Provincial de Pontevedra, MEC

The Mediterranean corn borer or pink stem borer (MCB, Sesamia nonagrioides Lefebvre) causes important yield losses as a consequence of stalk tunneling and direct kernel damage. B73 and Mo17 are the source of the most commercial valuable maize inbred lines in temperate zones, while the intermated B73 × Mo17 (IBM) population is an invaluable source for QTL identification. However, no or few experiments have been carried out to detect QTL for corn borer resistance in the B73 × Mo17 population. The objective of this work was to locate QTL for resistance to stem tunneling and kernel damage by MCB in the IBM population. We detected a QTL for kernel damage at bin 8.05, although the effect was small and two QTL for stalk tunneling at bins 1.06 and 9.04 in which the additive effects were 4 cm, approximately. The two QTL detected for MCB resistance were close to other QTL consistently found for European corn borer (ECB, Ostrinia nubilalis Hübner) resistance, indicating mechanisms of resistance common to both pests or gene clusters controlling resistance to different plagues. The precise mapping achieved with the IBM population will facilitate the QTL pyramiding and the positional cloning of the detected QTL., This research was supported by the National Plan for Research and Development of Spain (Project Cod. AGL2006-13140). B Ordas and R Santiago acknowledge a contract from the Spanish National Research Council (I3P Program) and G Sandoya acknowledges a fellowship from the Ministry of Education and Science (Spain)., MEC, CSIC

6 Pag., 4 Tabl., 1 Fig., Selection against pink stem borer (Sesamia nonagrioides Lef) (PSB) attack was performed in the maize (Zea mays L.) synthetic EPS12. The direct response of the EPS12 population to three cycles of selection to reduce tunnel length damage by PSB while maintaining yield was evaluated. S0 (cycles of selection) and S1 (selfed cycles of selection) generations and testcrosses to three testers were evaluated under artificial infestation with two corn borers, PSB and European corn borer (Ostrinia nubilalis Hubner) (ECB). Genotypes and the genotype × environment interaction were significant for tunnel length and yield. Differences among cycles of selection were significant for tunnel length, and the linear decrease for this trait (−1.80 cm cycle−1) achieved during selection accounted for most of these differences. Yield was not significantly reduced with selection. Inbreeding for yield significantly increased due to selection. EPS12 crossed to EP42 showed a significant increase in yield with selection, while crosses to other testers showed a nonsignificant reduction in yield. Although crosses to EP42 were not significantly different for tunnel length, the high heterosis between EPS12 and EP42 and the increased yield of EPS12 × EP42 during selection suggest that inbred lines developed from advanced cycles of EPS12 could be crossed to EP42 to generate promising hybrids. In general, resistance to PSB and ECB was improved, while yield was maintained, inbreeding was increased, and yield of the cross EP42 × EPS12 was improved.

The leaf sheaths of selected inbred lines of maize (Zea mays L.) with variable levels of stem resistance to the Mediterranean corn borer Sesamia nonagrioides (Lefèvbre) were evaluated for antibiotic effect on insect development. Phytochemical analyses of leaf sheaths were conducted for cell wall phenylpropanoid content to gain a better understanding of maize-resistance mechanisms. Laboratory bioassays established that sheath tissues from different genotypes significantly affected the growth of neonate larvae. Three hydroxycinnamates, p-coumaric, trans-ferulic, and cis-ferulic acids, and three isomers of diferulic acid, 8-5‘, 8-O-4‘, and 8-5‘ b (benzofuran form), were identified. Significant negative correlations were found between larvae weight and diferulic acid content for six genotypes. These results are in agreement with previous studies concerning the role of cell wall structural components in stem borer resistance.

In maize, Zea mays L., the timing of vegetative phase transition from juvenile to adult vegetative phases can be modified through selection. A reduction in the juvenile vegetative phase has been associated with resistance to diseases and pests. The major maize pest in temperate areas is Ostrinia nubilalis (Hübner) and in Europe Sesamia nonagrioides Lefebvre. The objective of our study was to determine the effects of divergent selection for the timing of vegetative phase transition in maize on resistance to corn borers. Three cycles of divergent selection for early and late phase transition in a field corn synthetic and in a sweet corn population were evaluated separately under S. nonagrioides and O. nubilalis artificial infestation. For the field corn experiment, yield and moisture improved with selection for phase transition in both directions, but improvement was due to artifacts of selection, rather than to the change in phase transition. There were no correlated responses for corn borer damage, yield, or grain moisture due to selection for the timing of vegetative phase transition. In the sweet corn experiment, selection for the timing of vegetative phase transition had no significant effects on corn borer damage in sweet corn harvested at the fresh stage. Our results do not support the use of phase transition as an indirect criterion for improving resistance to corn borers in maize. The relationship between phase transition and pest resistance reported by other studies could depend on the genotypes or could be too weak to be detected in a selection program with wild-type maize.

Flint maize, Zea mays L., varieties provide some interesting agronomic characteristics and kernels that possess a better ability than other kernels for developing high-quality flour. The pink stem borer, Sesamia nonagrioides Lefebvre, is an important constraint for the maize crop in Mediterranean regions. The objective of this work was to identify a >flint X flint> heterotic pattern that would perform well under artificial infestation by S. nonagrioides. A 10-population diallel was evaluated under infestation by S. nonagrioides in 2 yr. Variety effects were the only significant effects involved in stem and ear resistance to S. nonagrioides attack. Variety effects and average heterosis effects were the only significant effects for grain yield under artificial infestation conditions. Considering variety effects and cross-performance, the heterotic pattern Basto/Enano levantixo X Longfellow (BA/EL X LO) would be recommended for obtaining flint maize hybrids tolerant to S. nonagrioides attack because BA/EL had the most favorable variety effects for stem resistance, LO exhibited the most positive variety effects for grain yield, and the cross BA/EL X LO yielded significantly more than the remaining crosses.

[Background] Corn borers are the primary maize pest; their feeding on the pith results in stem damage and yield losses. In this study, we performed a genome-wide association study (GWAS) to identify SNPs associated with resistance to Mediterranean corn borer in a maize diversity panel using a set of more than 240,000 SNPs., [Results] Twenty five SNPs were significantly associated with three resistance traits: 10 were significantly associated with tunnel length, 4 with stem damage, and 11 with kernel resistance. Allelic variation at each significant SNP was associated with from 6 to 9% of the phenotypic variance. A set of genes containing or physically close to these SNPs are proposed as candidate genes for borer resistance, supported by their involvement in plant defense-related mechanisms in previously published evidence. The linkage disequilibrium decayed (r2, [Conclusions] Most of the candidate genes found in this study are part of signaling pathways, others act as regulator of expression under biotic stress condition, and a few genes are encoding enzymes with antibiotic effect against insects such as the cystatin1 gene and the defensin proteins. These findings contribute to the understanding the complex relationship between plant-insect interactions., This work was supported by the National Plan for Research and Development of Spain (projects AGL2012-33415). L.F. Samayoa acknowledges a contract JAE-Predoc from the Spanish Council for Scientific Research (CSIC).

Popcorn adapted to Spanish conditions could be an interesting and profitable alternative to field corn. However, little is known about breeding popcorn germplasm for adaptation to Spain. Sesamia nonagrioides Lefèvbre is the main insect pest affecting popcorn quality and yield under Spanish growing conditions. The objectives of the study were the search for sources of resistance to S. nonagrioides among popcorn germplasm and to study the genetics of the resistance to S. nonagrioides attack. Eight breeding populations along with a five-inbred line diallel and two popcorn commercial checks were evaluated under S. nonagrioides infestation in 2 yr. Significant differences were found among general combining ability (GCA) effects for days to silking, S. nonagrioides tunnel length, general appearance of the ear, kernel moisture, and yield. Specific combining ability (SCA) effects were found to be significant for yield and ear damage. Therefore, heterotic patterns among popcorn materials should be taken into account to generate new popcorn hybrids that are not only more productive but also have higher kernel quality. Breeding popcorn populations BSP4APC0 and PSPW1C1 could be base germplasms in a breeding program for obtaining parental inbreds of healthy kernel popcorn hybrids. New inbred lines could be generated from the cross BP1 × BP2 that would have improved GCA and SCA effects for S. nonagrioides resistance when crossed to South American inbreds

The most important insect pest of maize (Zea mays L.) in southern Europe is the pink stem borer (Sesamia nonagrioides Lef.). The objective of this work was to identify sources of resistance to stem and ear damage by the pink stem borer. One hundred twenty-one inbreds from seven germplasm groups (American, Argentine, European, Lancaster, Northern Flint, Reid, and Other), divided according to their maturity grouping (very early, early, midscason, and late), were evaluated for several years under artificial infestation at Pontevedra (northwestern Spain). Twelve traits were recorded to measure stem and ear damage. Stem and ear damage resistance traits were not correlated, therefore simultaneous selection for the two types of resistance within the same population should be carried out. Eight very early, two early, seven midseason, and four late inbreds were resistant to stem-damage. The Reid germplasm group was more resistant to stem attack than the other groups. Therefore, the best Reid inbreds could be used to form a stem-damage resistant Reid synthetic, which could be a source of new stem-damage resistant varieties. Simultaneously, the best non-Reid inbreds could be used for making a non-Reid stem-damage resistant synthetic. Thirteen very early, 10 early, two midseason, and three late inbreds performed better than the others against ear attack. Only seven inbreds (A509, A635, CO125, EA2024, EP39, Oh43, and PB130) were resistant to both stem and ear damage. These inbreds could be used as sources of resistance to pink stem borer in a breeding program., 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)., MCYT, Xunta de Galicia

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)., MCYT, Xunta de Galicia

The stem borer Sesamia nonagrioides (Lefebvre) is the main pest of maize, Zea mays L., in northwestern Spain. The inheritance of the stalk resistance to this maize borer is unknow. The objective of this work was to study the inheritance of antibiosis to Sesamia in maize stalks. Three maize inbreds with different stalk resistance levels to S. nonagrioides were used and 2 crosses were made: CM109 × EP31 (resistant × medium resistant) and CM109 × EP42 (resistant × susceptible). For each cross, 6 generations, consisting of the P1, P2, F1, F2, and backcrosses (BC1 and BC2), were evaluated for 2 yr. Additive, dominance, epistatic, environmental effects, and the genotype × environment interaction were estimated from generation mean analysis. Correlation coefficients among stalk damage traits showed that tunnel length was a good indicator of stalk resistance to Sesamia. The inheritance of stalk resistance to Sesamia is under genetic control. The additive-dominance model without nonallelic and genotype × environment interactions fit the generation mean analysis for both crosses, but gene action differed from one cross to another. For the cross CM109 × EP31, the additive and dominance gene effects were significant and had, in general, similar importance; whereas for CM109 × EP42, stalk resistance involved largely additive effects. A recurrent selection approach should be used to improve resistance to Sesamia combining additive and dominance gene effects or considering only additive effects, depending on the cross evaluated. Resistance was dominant to susceptibility. The resistant inbred CM109 could be used as a donor of stalk resistance.

[EN] The pink stem borer (PSB) (Sesamia nonagrioides Lefèbvre, 1827; Lepidoptera: Noctuidae) is the main insect pest of maize ( Zea mays L., Poaceae) in the Mediterranean area. Maize varieties partially resistant to PSB have been identified, but few studies have documented the mechanisms of resistance involved. The objectives of this research were to study the levels of leaf and sheath antibiosis of a maize population, EPS12, and determine whether antibiosis improved over the selection process for less stalk tunneling. A hybrid check and two Bacillus thuringiensis (Bt) hybrids were also examined. Several bioassays were carried out in a control chamber to evaluate antibiosis of maize leaves and sheaths against PSB larvae. Leaf antibiosis was significantly higher for EPS12 than for the hybrid check and sheath antibiosis was low for all non-Bt hybrids studied. We conclude that leaf and sheath antibiosis was not significantly improved during the selection process. Future efforts should look for other possible mechanisms of resistance, such as stem rind antibiosis., [FR] La sésamie du maïs (PSB; Sesamia nonagrioides Lefèbvre, 1827; Lepidoptera : Noctuidae) est le principal insecte ravageur du maïs (Zea mays L., Poaceae) de la région méditerranéenne. Des variétés de maïs partiellement résistantes à la sésamie (PSB) ont été identifiées, bien que peu d’études aient abordé les mécanismes de résistance impliqués. Les objectifs de notre recherche consistent à étudier l’antibiose au niveau des feuilles et de la gaine d’une population de maïs EPS12 et de vérifier s’i lyaamél ioration de l’antibiose lorsque nous faisons une sélection pour diminuer le taux de perçage des tiges. Nous avons aussi testé un témoin commercial hybride et deux hybrides Bt (Bacillus thuringiensis). Nous avons procédé à plusieurs bioessais dans des chambres de culture contrôlées afin de vérifier l’antibiose des feuilles et des gaines de maïs aux larves de sésamie (PSB). L’antibiose des feuilles est significativement plus élevée chez EPS12 que chez le témoin commercial hybride et celle des gaines est faible chez toutes les variétés non Bt étudiées. En conclusion, le processus de sélection n’améliore pas significativement l’antibiose des feuilles et des gaines. Les études futures devraient rechercher d’autres mécanismes de résistance, tels que l’antibiose du cortex de la tige., This research was funded by the Ministry of Education and Science (AGL2000–0944-C02–01), Spain, and the Excma. Deputación Provincial de Pontevedra, Spain., MICINN, Excma. Deputación Provincial de Pontevedra

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 (Hübner)]. 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., P. Velasco acknowledges a fellowship from the Excma. Diputación Provincial de Pontevedra. The authors thank E. Muiños for her help in rearing insects. Research was supported by the Project XUGA 40301B98., Diputación Provincial de Pontevedra, Xunta de Galicia

Corn borers are the main pests of maize, Zea mays L., in temperate areas. In Spain and other Mediterranean countries, the principal corn borer is Sesamia nonagrioides Lefebvre, although the European corn borer, Ostrinia nubilalis (Hubner), is also an important pest in sweet corn. The objectives of this work were to study resistance to attack of both species in sweet corn populations and to compare the mechanisms of resistance. Twenty sweet corn populations and 1 field corn population were evaluated for ear resistance under artificial infestation, with eggs of S. nonagrioides and O. nubilalis, under natural conditions, and protected with an insecticide, in 1996 and 1997. There were significant differences between years and the interactions genotype × year and treatment × year were significant for most traits. In 1996, damage produced by S. nonagrioides was greater than damage produced by O. nubilalis. In 1997, attack of O. nubilalis was most important. The insecticide did not protect the crop in 1996, and protection was low in 1997. The field corn synthetic cultivar ‘BSCB1(R)C11’, and the sweet corn synthetic cultivars ‘NE-HY-13A(S)C1’, ‘NE-HY-13B(S)C1’, and ‘AS11’ were resistant to attack by both species in both years. Stowell’s ‘W. Evergreen’ and ‘EPS11’ were resistant to O. nubilalis and showed some resistance to S. nonagrioides. All resistant populations have field corn in their pedigree. Field corn seemed to be more resistant than sweet corn, and mechanisms of resistance to both pests were not entirely independent.

Yield under infestation by the pink stem borer [Sesamia nonagrioides (Lefebvre)] has been proposed as the best estimator of maize (Zea mays L.) performance under pink stem borer attack. Yield is a complex trait that greatly interacts with the environment. Several methods could be used to study the genotype × environment (GE) interaction. The objective of this work was to study the GE interaction for yield of 49 maize hybrids in five different environments by the Site Regression (SREG) and factorial regression methods. Locations presented different levels of natural infestation by the pink stem borer. The biplot obtained by applying the SREG method allowed visual cultivar evaluation. The factorial regression method incorporated genotypic and environmental covariates that enhanced biological interpretation of GE interaction. Hybrid A637 × EP42 would be recommended in northwestern Spain under medium and high natural infestation by the pink stem borer because it showed high and stable yielding ability. Genotypic and environmental covariates explained approximately 75% of the GE interaction variation, but other genotypic covariates could be introduced in the model to reduce GE residual variation to a nonsignificant level. In general, GE effects for grain yield were mainly due to earliness, vigor effects, and environmental yield limiting factors such as the mean of minimum temperature and percentage of air humidity.