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

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

Allozyme frequencies, heterozygosity and genetic distances following S1 recurrent selection in two synthetic maize populations

Three cycles of S1 recurrent selection for yield were carried out in two synthetic maize populations, EPS6 from humid Spain and EPS7 from arid Spain. One-hundred S1 lines were evaluated from each cycle of selection and the ten highest-yielding S1 lines were recombined to produce the next cycle. Changes in variability and genetic distances in two synthetic maize populations, following three cycles of recurrent selection, recombining ten S1 lines in each cycle, were determined. Isozyme analysis was performed on 125 seedlings per cycle of selection (four cycles in each of two populations). Regressions of each allozyme frequency on cycles of selection were performed, genetic distances between populations were determined, and simple correlations between genetic distances and heterosis were calculated. The average heterozygosity per locus was also calculated for each population. Regression analysis did not reveal any common trend between EPS6 and EPS7 for changes in allele frequencies presumably due to selection. The number of polymorphic loci, the mean alleles per locus, and the mean heterozygosity did not show any reduction in variability. Finally, selection did not affect genetic distances among cycles of selection. The agronomic evaluation of the selection program, after three cycles of selection, revealed that the genetic variance was not significantly reduced for most traits, and that the heterosis among cycles of selection of both populations had not changed significantly. The conclusions based on isozyme data supported the deductions made from agronomic data. Three cycles of selection neither caused relevant changes on variability nor on genetic distance among cycles of selection of both maize synthetic populations. These data did not indicate any basis for increasing the number of S1 lines recombined for recurrent selectionResearch supported by the Committee for Science and Technology of Spain (project cod. AGF95-0891-C02-01) and Excma. Diputación Provincial de Pontevedra, Spain. M.I.Vales acknowledges a fellowship from the Excma. Diputación Provincial de Pontevedra.MCYTDiputación Provincial de PontevedraN

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

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

Six cycles of selection for adaptation in two exotic populations of maize

The maturity rating of maize (Zea mays L.) grown in Galicia (Northwestern Spain) varies from FAO 200 to 600. Later germplasm has usually too much moisture content in the kernel at normal harvesting time so serious problems with storing could appear. Besides, farmers have tended to use earlier varieties in the last few years. All this imposes limitations on the amount of germplasm available to develop varieties adapted to this area.To study the possibility of adapting late, exotic material to the environment of the Atlantic coast of Galicia we carried out six cycles of individual selection on two non-adapted populations of maize (Purdue A and Purdue B). The criterion of selection was early silking and the criterion of response was moisture content of kernel at harvesting.The original populations and the populations obtained after each cycle of selection were crossed to the hybrids CM105 × CM109 (tester Reid) and H99 × H95 (tester Lancaster) and were evaluated in four environments to study the efficiency of the selection scheme. There were significant reductions in days to silking (6.1 and 6.7 days from cycle 0 to cycle 6 for Purdue A and Purdue B, respectively) and grain moisture at harvesting (3.0 and 3.9% from cycle 0 to cycle 6 for Purdue A and Purdue B, respectively). There were also reductions in plant height and yield in both populations.In general, the crosses ‘population × Lancaster’ were higher for yield than the crosses ‘population × Reid’. Yield of the population crosses by both testers decreased after the six cycles of selection probably because of the earlier maturity of the selected populations. Some inbreeding depression may also have occurred.Diputación Provincial de PontevedraPeer reviewe

Recurrent selection for grain yield in two Spanish maize synthetic populations

The most common maize (Zea mays L.) heterotic pattern in Europe is European flint × U.S. dent. Northern Spain × southern Spain has been proposed as an alternative heterotic pattern. Three maize synthetic populations, namely EPS6 from northern Spain, EPS7 from southern Spain, and EPS10 formed by early American populations, were produced in Pontevedra, Spain. Because of their low yield, the two Spanish synthetic populations were subjected to three cycles of intrapopulation S1 recurrent selection for grain yield. Our objectives were to evaluate the effect of selection on grain yield and other agronomic traits, and to determine the changes in heterosis and general (GCA) and specific (SCA) combining ability brought about by selection. The three original synthetic populations, the three cycles of selection of the two Spanish synthetic populations, and the crosses among the original and the improved cycles were evaluated in two locations in northwest Spain in 1994 and 1995. Yield significantly increased with selection in both Spanish synthetic populations. The GCA improved with selection in both EPS6 and EPS7. Heterosis and SCA did not change significantly with selection. The third cycles of each Spanish synthetic would be the most appropriate maize populations to start a reciprocal recurrent selection to improve the heterotic pattern northern Spain × southern Spain.M. Isabel Vales acknowledges a fellowship from the Diputación Provincial de Pontevedra.Peer reviewe

Inheritance of resistance to ear damage caused by Sesamia nonagrioides (Lepidoptera: Noctuidae) in maize

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 crosses and the degree of genetic control varied depending on the cross and trait. For both crosses, additive and dominance effects were significant for most ear damage traits. Epistatic gene effects were significant for husk and shank damage, and gene effects for number and length of tunnels were not significant. Because ear resistance involved additive and dominance effects for this set of inbreds, breeding procedures based on both types of gene action should be effective.The authors thank E. Muiños for her help in rearing insects. M.I.V. acknowledges a fellowship from the Excma. Diputación Provincial de Pontevedra. A.B. acknowledges a fellowship from the Consejo Superior de Investigaciones Científicas. This research was supported by the Committee for Science and Technology of Spain (project AGF92-0161) and by the Department of Education of the Autonomous Government of Galicia (project XUGA 40301B95).Diputación Provincial de PontevedraCSICMCYTXunta de GaliciaPeer reviewe

Inheritance of antibiosis to Sesamia nonagrioides (Lepidoptera: Noctuidae) in maize

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.Peer reviewe

Integración de patrones heteróticos de maíz dulce y grano

Trabajo presentado en las XI Jornadas de selección y mejora de plantas hortícolas, celebradas en Córdoba (España), entre el 21 y el 23 de octubre de 1998.- 8 páginas y 4 tablas.[EN] Field corn (Zea mays L.) heterotic patterns could improve the sweet corn heterotic patterns. The objective of this work was to determine the most efficient crosses to integrate these field and sweet corn heterotic patterns. A dialIel among the sweet corn populations Country Gentleman, Golden Bantam and Stowell ´s Evergreen, and the fíeld corn synthetics EPS6(S)C3, EPS7(S)C3 and EPS10 was evaluated two years, at two locations in northwestern Spain. Differences for helerosis effects (hjj) and average heterosis (h) were significant for all but grain moisture. Differences for variety heterosis (hj) and specific heterosis (Sjj) were significant for yield, plant height and row number. The best field corn heterotic pattern woulld be EPS6(S)C3 x EPS10, followed by EPS6(S)C3 x EPS7(S)C3, and for sweet corn Golden Bantam x Country Gentleman, followed by Golden Bantam x Stowell's Evergreen. The best choice for integrating the heterotic patterns would be (EPS6(S)C3 x Golden Bantam) x (EPS7(S)C3 x Stowell' s Evergreen).[ES] Los patrones heteróticos existentes en maíz (Zea mays L,) grano podrían ser de utilidad para mejorar los de maíz dulce. El objetivo de este trabajo fue determinar los cruzamientos más eficientes para integrar los patrones heteróticos de maíz grano y los de maíz dulce. Un diaIelo entre las poblaciones de maíz dulce Country Gentleman, Golden Bantam y StoweII's Evergreen y los sintéticos de maíz grano EPS6(S)C3, EPS7(S)C3 y EPS10 fue evaluado durante dos años en dos localidades en el noroeste de España. Las diferencias para efectos heteróticos (hjj) y heterosis medias (h) fueron significativas para todos los caracteres excepto humedad de grano. Las diferencias para heterosis varietales (hj) y heterosis específicas (sjj) fueron significativas para rendimiento, altura de planta y número de filas. El mejor patrón heterótico de maíz grano sería EPS6(S)C3 x EPS10, seguido por EPS6(S)C3 x EPS7(S)C3, y para maíz dulce Golden Bantam x Country Gentleman, seguido por Golden Bantam x Stowell' s Evergreen. La mejor elección para integrar los patrones heteróticos sería (EPS6(S)C3 x Golden Bantam) x (EPS7(S)C3 x Stowell' s Evergreen).Peer reviewe

Heterosis en cruzamientos entre líneas de maíz dulce y de maíz grano

Comunicación presentada en las X Jornadas de selección y mejora de plantas hortícolas, celebradas en Vitoria entre el 24 y el 26 de septiembre de 1996.- 7 páginas y 3 tablas.[EN] Heterotic patterns are not presently defined among sweet corn inbreds. Field corn heterotic groups could be valuable for sweet corn breeding. The objective of this work was to compare the performance of crosses of sweet corn by field corn inbreds from diverse heterotic patterns. Eleven field corn inbreds, consisting of European and American germplasm adapted to Northwestern Spain, were crossed to five susu and two susu sese sweet corn inbreds. Crosses were evaluated along with checks in a 10x10 simple lattice design. Inbreds were evaluated in randomized complete block designs. Neither the germplasm background nor the heterotic group of the field corn inbreds were related to heterosis in crosses of sweet by field corn. The conversion of field corn heterotic patterns into sweet corn presumes that performance of crosses of field corn by sweet corn would differ for diverse heterotic groups. Therefore, these results do not encourage investments to capitalize field corn heterotic patterns for straight conversions to sweet corn.[ES] Actualmente no existen patrones heteróticos entre las líneas puras de maíz dulce. Los grupos heteróticos de maíz grano podrían ser útiles en maíz dulce. El objetivo de este trabajo fue comparar la heterosis en cruzamientos entre líneas de maíz dulce y líneas de maíz grano pertenecientes a distintos grupos heteróticos. Once líneas de maíz grano europeas y americanas fueron cruzadas con 5 líneas de maíz dulce y 2 líneas de maíz superdulce susu sese. La heterosis no estuvo relacionada con el tipo de germoplasma de la línea de maíz dulce ni con el grupo heterótico de la línea de maíz grano. La conversión de patrones heteróticos de maíz grano a maíz dulce presupone que líneas de maíz grano de distintos grupos se comporten diferentemente cuando se crucen con líneas de maíz dulce. Por tanto, estos resultados no apoyan la realización de grandes esfuerzos para aprovechar los patrones heteróticos de maíz grano convirtiendo las líneas de maíz grano directamente en dulces.Peer reviewe

Cultivar heterosis between sweet and Spanish field corn

Field corn (Zea mays L. var. mays) cultivar heterosis could improve sweet corn (Zea mays L. var. rugosa Bonaf) heterotic patterns. Two Spanish field corn (Su) and two sweet corn (su) heterotic patterns have been reported previously. The objective of this study was to determine which sweet × field corn crosses could be used to improve sweet corn heterotic groups. A diallel among three sweet corn cultivars (`Country Gentleman', `Golden Bantam', and `Stowell's Evergreen') that are representative of the variability among modern sweet corn cultivars, and three field corn synthetic cultivars [`EPS6(S)C3', `EPS7(S)C3', and `EPS10'] representing the heterotic patterns involving Spanish field corn, was evaluated for 2 years at two locations in northwestern Spain. Differences in heterosis effects (hjj') and average heterosis (h) were significant for all traits except grain moisture. Differences for cultivar heterosis (hj) and specific heterosis (sjj') were significant for grain yield, plant height, and kernel row number. `EPS6(S)C3' had lower sjj' for yield in crosses to `Golden Bantam' than to `Stowell's Evergreen', while `EPS7(S)C3' had higher sjj' in crosses to `Golden Bantam' than to `Stowell's Evergreen'. The best crosses to establish enhanced sweet corn heterotic patterns involving Spanish maize would be `Golden Bantam' × `EPS6(S)C3' and `Stowell's Evergreen' × `EPS7(S)C3'. New sugary 1 cultivars would require preliminary cycles of intrapopulational recurrent selection for agronomic performance and flavor prior initiating an interpopulational recurrent selection program to enhance heterosis.Peer reviewe