Maize Accessions Research Articles

Resistance in maize to the Larger Grain Borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae)

Abstract Host plant resistance in maize can be a useful component of Integrated Pest Management (IPM) of the Larger Grain Borer (LGB), Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae). The germplasm bank of the International Maize and Wheat Improvement Centre (CIMMYT) has more than 14,000 maize accessions from all over the world. In 1993, from the seed regeneration nursery of Caribbean land races, 105 land races were selected using good plant type as the criterion. When grains of these land races were infested with LGB in the laboratory, 19 showed resistance as evidenced by the low amount of powder (chewed uneaten maize plus feces) formed 140 days after the infestation. Through a series of infestation, selection and inbreeding (self-pollination of land races) over four generations, S 3 maize ears were generated. These ears showed a high level of resistance as indicated by a low powder production relative to the susceptible control. The LGB reproduction was adversely affected on resistant ears as indicated by the small size of adult populations. Thus, antibiosis could be the mechanism of resistance operating within the S 3 progenies of selected land races. Such sources of resistance can be very useful in developing maize populations/hybrids for use in IPM of LGB.

Heterotic responses of tropical elite maize accessions from Latin America with Brazilian testers

Little emphasis has been placed on identifying new sources of tropical maize germplasm that can be used in breeding programs. Additional information on the performance and heterotic classification of tropical germplasm is needed. This study was conducted to identify elite maize accessions from Latin America that could contribute to increase the level of heterosis with the best heterotic patterns of Brazil. Seventy-two elite accessions from the Latin American Maize Project (LAMP) were crossed with the testers BR 105 (flint kernel Suwan background) and BR 106 (dent kernel Tuxpeño background). The 72 crosses plus 9 checks were evaluated using a simple 9 × 9 lattice in four locations that represent one tropical region. The combined analysis showed highly significant differences among treatments for ear weight and the interaction treatment × location was also significant. With both testers better crosses for ear weight were identified in relation to the double cross BR 201 (commercial check). With the tester BR 105, the high parent heterosis ranged from --28% to 26%, the accessions SE 032 and PE 001 were selected for further work. With the tester BR 106, the high parent heterosis ranged from --35% to 17% and the accessions PE 011 and Pasco 14 were selected for further work. The selected accessions will be improved through recurrent selection schemes to increase yield and improve agronomic traits. Afterwards they can be exploited, within and between heterotic groups, to produce highly productive hybrid combinations, or used per se as improved maize varieties.

Accumulation of amino acids, proline, and carbohydrates in response to aluminum and manganese stress in maize

Synthesis of amino acids, proline, and carbohydrates was studied in roots and shoots of 5 maize accessions, differing in aluminum (Al) and manganese (Mn) tolerance, in response to Al and Mn stress at the seedling stage in solution culture. The concentrations of these metabolites increased in roots and shoots of the seedlings in the nutrient solution with added Al (0.22 mM), and Mn (2.0 mM). Both Al and/or Mn tolerant and non‐tolerant accessions accumulated more metabolites under stress than control. Generally, the tolerant accessions accumulated more solutes than the non‐tolerant maize accessions examined.

Stewart's Wilt Reactions of an International Collection of Zea mays Germ Plasm Inoculated with Erwinia stewartii.

Maize accessions were evaluated in 1997, 1998, and 1999 to identify additional sources of Stewart's wilt resistance and to determine if reactions differed among accessions collected from various regions of the United States and throughout the world. The distributions of Stewart's wilt reactions rated from 1 (no appreciable spread of symptoms) to 9 (dead plants) were relatively similar among groups of accessions from all regions of the world except for those from the Mid-Atlantic/Ohio River Valley region of the United States, the southern United States, and the northeastern United States. The mean and median Stewart's wilt rating for 1,991 accessions evaluated in 1997 was 4. The mean Stewart's wilt rating for 245 accessions collected from the Mid-Atlantic/Ohio River Valley region was 3.1, which was significantly lower than that for accessions from all other regions. The mean rating for accessions from the southern United States was 3.7, which also was lower than mean ratings for accessions from all other regions. Ratings from trials in 1997 and 1998 were highly correlated (r = 0.87) for 292 accessions and 15 sweet corn hybrid checks evaluated in both years. Of 20 accessions rated below 2 in 1997 and 1998, seven were from Virginia, seven were from the Ohio River Valley or central Corn Belt of the United States, four were from the northern or western Corn Belt of the United States, and two were from Spain. Ratings for these accessions ranged from 1.7 to 3.1 in 1999. Ratings ranged from 2.6 to 3.7 for F1 hybrids of these accessions crossed with one of two susceptible sweet corn inbreds, CrseW30 or Crse16, which were rated 5.7 and 5.4, respectively. Based on the reactions of this collection of germ plasm, it appears that high levels of Stewart's wilt resistance are prevalent only among accessions collected from areas where the disease has been endemic for several years, whereas moderate levels of resistance can be found in accessions collected from nearly everywhere in the world.

Variation among Andean races of maize for cold tolerance during heterotrophic and early autotrophic growth

Cold in the initial growth stages is an important stressfactor for maize grown in regions with a temperate climate,particularly in case of early sowing. Sources of tolerancehave been identified in adapted genotypes, but promisinggenes for cold tolerance should also be found in materialdeveloped under the lower-temperature margins of the cropdistribution. This research was conducted in order to testAndean maize accessions for cold tolerance expressed duringboth the heterotrophic and early autotrophic growth stages.Experiments were conducted in controlled environments tostudy cold tolerance traits (germination %, germinationindex and plant growth rate) at continuous 10°C (heterotrophic growth) and at varying 10–16°C (autotrophic growth). An experiment was also performed inthe field with early sowing (both heterotrophic and autotrophic growth). In each experiment, a control trialwas conducted in more favourable conditions (i.e. continuous25°C in a controlled environment or late planting inthe field) so that cold tolerance traits could also beexamined as the ratio between the stress and the controltrial. None of the accessions was superior for all coldtolerance traits. However, several Andean maize accessionsoutperformed the US Corn-belt hybrid checks for one or moretraits, both in heterotrophic and autotrophic growth. Overall, BOZM 855, PMS 636, Poblacion D, Poblacion E andBOZM 696 were the best accessions, suggesting that they canbe a promising source of genes for improving cold toleranceof adapted maize genotypes.

Genetic relationships among Native American maize accessions of the Great Plains assessed by RAPDs

Genetic variation among 15 accessions of Native American maize from the Great Plains was investigated using random amplified polymorphic DNA (RAPD). RAPDs revealed very high levels of polymorphism among accessions. Banding patterns ranged in percentage polymorphism from 46.7% to 86.2% with an overall mean of 70.7% for the primers analyzed. The construction of genetic relationships using cluster analysis and principal coordinates analysis revealed that RAPDs are successful in confirming hypothesized relationships and in identifying misclassified specimens. Furthermore, the phenogram fails to reveal a strong correspondence between genetic relationships and the geographical position of Native Americans prior to contact. This provides support for the hypothesis that multiple introductions of maize into the Great Plains via trade may have resulted in the great morphological variation found among accessions in the region. Based on these data, it is unlikely that a separate Great Plains race of maize can be distinguished. In general, we conclude that RAPDs are potentially very useful in organizing seed collections and understanding intraspecific genetic differentiation.

A Two‐Stage, Three‐Way Method for Classifying Genetic Resources in multiple Environments

Cluster analysis is commonly used when gene bank accessions are evaluated in different environments and several continuous and categorical attributes are measured. The objectives of this study were (i) to develop a two‐stage classification strategy for three‐way data (accession × attribute × environment) using the Modified Location Model (MLM) with categorical and continuous variables and (ii) assess this approach for classifying observations of one simulated data set (with known structure) and two experimental data sets consisting of multi‐attribute, multi‐site field trials of Caribbean and Cónico accessions of maize (Zea mays L.). Clusters were compared including and excluding the categorical variables. Results from the simulated data showed good recovery of the group structure and a balanced effect of both categorical and continuous variables on the classification. The two‐stage, three‐way MLM method formed well‐defined groups of accessions and characterized them based on the continuous as well as the categorical variables. As expected, groups formed using only continuous variables showed no clear response patterns concerning the categorical variables; however, those formed using both types of variables had clear response patterns with respect to each type. Furthermore, groups of Caribbean accessions showed dear association with geographical origin. The MLM model should be useful for classifying genetic resources evaluated in multi‐environment trials into homogeneous groups with the objective of forming core subsets. When a large number of categorical variables are combined across environments, the MLM may not improve the initial classification obtained from hierarchical clustering strategy.

Evaluation of Carribean Maize Accessions to Develop a Core Subset

Core subsets of germplasm collections facilitate their evaluation and use. Field evaluations were conducted to develop a core subset of Caribbean maize (Zea mays L.) accessions from the CIMMYT maize germplasm bank. Most accessions were from the West Indies and others were from Central and South America. The accessions were divided into two trials of 249 accessions and seven common checks that were evaluated in a 16 by 16 α‐lattice design with two replications. The trials were planted in two seasons at two sites in Mexico during 1992 through 1994. Data were taken on agronomic and morphological traits and the combined analysis was performed by a mixed linear model. The adjusted means of plant height, ear height, senescence, ear diameter, ear length, days to silk, days to anthesis, moisture (%), rating on ease of shelling, and number kernel rows were used to cluster accessions into homogeneous groups. Twelve non‐overlapping clusters were formed and patterns of phenotypic diversity among and within clusters were determined using canonical discriminant analysis. A selection index based on yield (Mg ha−1), ear rot (%), erect plants (%), and moisture (%) was calculated for each accession. The upper 20% of the accessions (100 in total) which represent the phenotypic diversity of the clusters and have superior selection indexes were used to form a core subset of the Caribbean maize collection.

Evaluación de las características cuantitativas de 25 accesiones de maíz (lea mays L.) de la zona andina

Con el objeto de evaluar morfológicamente 25 accesiones de maíz (Zea mays L.) de la zona andina, consignadas en el Banco de Germoplasma de ICA-CORPOICA, se aplicó una metodología propuesta por el Centro Internacional de Mejoramiento de Maíz y Trigo (CIMMYT ) que emplea 27 descriptores relacionados con la planta, la mazorca y el grano. El maíz se sembró en surcos de 10m de longitud, con uno a cinco surcos por parcela para cada accesión. En cada una de las parcelas se evaluaron 10 plantas en plena competencia para los caracteres varietales en estudio. Los datos se analizaron mediante estadísticas simples: desviación estándar, coeficientes de variación y correlaciones; para clasificar las accesiones se usaron análisis multivariados de variables canónicas y análisis de conglomerados (cluster). Los resultados mostraron que las primeras cinco variables canónicas explicaron el89% de la variación total; las variables con mayor contribución fueron peso de la mazorca, número de granos por 100 gramos, número de granos por hilera, altura de la planta, ancho de la lámina foliar y posición de la mazorca. Del análisis de agrupamientos, realizado mediante graficación en un plano cartesiano con base en las dos primeras variables canónicas, se pudo inferir que existe diversidad genética en las accesiones de maíz evaluadas, lo cual permitió clasificar las mismas en 7 grupos uniformes según las características morfológicas discriminantes y su lugar de origen.

Breeding Potential of Maize Accessions from Argentina, Chile, USA, and Uruguay

The Latin American Maize Project (LAMP) evaluated nearly 12 000 maize (Zea mays L.) accessions in 12 countries to select germplasm that can be used in breeding programs to improve commercial materials. In Argentina, Chile, Uruguay, and the USA, 1692 and 988 native accessions were evaluated in the first and second period, respectively. Sixty‐nine selected accessions were evaluated in all countries in the third stage. Accessions per se showed silk delay, indicating a lack of adaptation. The 69 selected accessions topcrossed with B73 × B14A, Oh43 × MolT, and SR76 were evaluated in the four countries to (i) identify temperate accessions from Latin America and the USA that could enhance yield, tassel and silk synchronization, lodging resistance, and maturity; and (ii) identify the U.S. heterotic group to which the accessions belong. The topcross results identified germplasm equal or superior to the performance of the checks in all countries, indicating that selected germplasm could be used to increase yield. Even though topcrosses showed significant improvement for silk delay and stalk lodging across the accessions, additional improvement is needed to facilitate wider use of the material. The Argentinean accessions had the best mean per se and topcross performance. Some accessions performed well in most countries and should be included in cooperative enhancement efforts.

Variability in aluminium and manganese tolerance among maize accessions

Tolerance to aluminium and manganese toxicity at the seedling stage for 72 maize accessions was examined in solution culture. 0.22 mM Al and 2.0 mM Mn gave better genotypic separation for aluminium and manganese tolerance assessed on the basis respectively of relative root length, and visual symptoms of leaf chlorosis and necrosis. There was considerable variability among accessions for tolerance to aluminium and to manganese. Three accessions, Bozm 1335, Bozm 1337, and Bozm 1536 showed tolerance to Al, while 4, Chzm 01009, Champ, Bozm 0715, LG 20.80 exhibited tolerance to Mn. Accession, Zea 769 was tolerant to both metals. A significant Al x Mn interaction was found when five accessions were grown in a mixture of 0.22 mM aluminium and 2.0 mM manganese. Root length inhibition in Al alone was slightly ameliorated when the accessions were grown in the Al + Mn solution. Tolerance to aluminium and manganese does not necessarily coincide, different mechanisms being involved in tolerance to the two metals.

Identifying Subsets of Maize Accessions by Three‐Mode Principal Component Analysis

Gencbank accessions are a potential source of genetic variability for maize (Zea mays L.) breeding programs. Identification of useful individual entries is commonly based on the expression of one or more attributes in different sites or environments. This study was motivated by the need to identify a subset of Caribbean accessions for introgression in to elite germplasm of the western Corn Belt. Thus the objective was to identify potentially useful Caribbean accessions, based on (i) simultaneous consideration of six agronomic attributes deemed economically important for the western Corn Belt, and (ii) response patterns observed across four sharply contrasting environments. Both (i) and (ii) were addressed by means of three‐mode principal component analysis (PCA) of data on six agronomic and morphological attributes for 184 Caribbean maize accessions evaluated at four environments. Three‐way data were analyzed by three‐mode PCA and based on (i) and (ii), two joint plots were generated. From the PCA and joint plots, two subsets of accessions were identified. First, a subset of 14 accessions having body yield, intermediate plant height, and average days to anthesis was identified. Secondly, a subset of 10 accessions having average performance over all environments was identified. Two accessions were common to both subsets. Jointly, the two approaches produced a combined subset of 22 accessions, representing 12% of the total evaluated, and including representatives of 11 maize races. Three‐mode PCA integrated information on accessions, attributes, and environments, and provided a means of simultaneously visualizing these three types of information. Three‐mode PCA can complement standard methodologies used by plant breeders for identification of potentially useful accessions in introgression programs.

Classifying Mexican Maize Accessions Using Hierarchical and Density Search Methods

Cluster analysis is commonly used for studying genetic diversity. Problems with hierarchical cluster analysis include how to combine different types of variables (discrete and continuous), choosing distance measurements, applying an appropriate clustering strategy, designating the optimal number of clusters, and identifying variables with significant discriminatory power. Hierarchical clustering methods are only descriptive and do not represent probabilities for classifying individuals into groups. The objectives of this study were to: (i) examine the performance of different cluster strategies based on several criteria, (ii) propose a classification method for germplasm accessions with statistical properties, and (iii) examine how the results of the proposed classification classification method can be applied to form core subsets. Morphologic and agronomic attributes collected for 115 Mexican maize (Zea mays L.) accessions, grouped in five races, from the Latin America Maize Project (LAMP) were subjected to the hierarchical cluster algorithms UPGMA (arithmetic mean method), Centroid, Median, and the Ward method. Two other techniques were studied, Density and the Normix (Nor) density search methods, which were both restricted continuous variables. The Nor method was applied to groups formed “a priori” by means of the hierarchical methods UPGMA, Centroid, Median, and Ward and resulted in subgroups denoted as NorU, NorC, NorM, and NorW, respectively. The NorW method formed five well defined groups of accessions and was an appropriate strategy for grouping accessions into relatively homogeneous groups. Strategies UPGMA, NorU, Centroid, NorC, Median, NorM, and Density were not very effective for classifying accessions into homogeneous groups. Different subsets can be formed based on the characteristics of the five homogeneous groups formed by NorW.

Identification of Agronomicaily Superior Latin American Maize Accessions via Multi‐Stage Evaluations

Few data exist regarding the agronomic utility of tens of thousands of available tropical maize (Zea mays L.) racial accessions. A long‐term, multi‐stage evaluation project has been developed at North Carolina State University to evaluate the breeding potentials in the temperate USA of typical Latin American maize germplasm collections. Agronomic evaluations of accessions per se were performed in daylength neutral environments. Superior accessions were crossed to a temperate‐adapted inbred line and converted to photoperiod‐insensitive 50%‐exotic and 75%‐exotic populations by selection during 1986 to 1990. These semi‐exotic populations were evaluated as testcrosses to Corn Belt testers in North Carolina during 1993 and 1994. Testcrosses of many 75%‐exotic families were higher‐yielding than the hybrid tester, B73Ht × Mo17Ht, providing evidence that agronomically superior Latin American maize accessions possess favorable genes for yield that apparently are absent from Corn Belt germplasm. Yields of accessions evaluated as 100%‐exotic and 50%‐exotic populations were significantly correlated (r = 0.62, P = 0.005) with each other, but not with yields of 75%‐exotic populations. Some accessions exhibited extreme ranking changes across different testing stages. Multi‐stage evaluations of maize racial accessions successfully identified superior germplasm for use by U.S. breeders, but there is no guarantee that all of the most valuable accessions were advanced to later testing stages. Evaluations in many environments and minimal culling levels at each stage could be used to improve the probabilities of successfully identifying useful accessions in future multi‐stage evaluation procedures.

Variation among maize (Zea mays L.) accessions of Bendel State, Nigeria

Variability in maize zein protein band mobilities in sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was characterized to classify 27 maize accessions (OTUs) collected from Bendel State, Nigeria. The classification of the OTUs was achieved using two numerical procedures: average linkage cluster analysis and principal component analysis (PCA).

Fatty acid composition of oil from exotic corn breeding materials

AbstractThe fatty acid composition of corn oil can be altered to meet consumer demand for “healthful” fats. The first step in altering the oils is to survey existing corn breeding materials for fatty acid composition. The Latin American Maize Project (LAMP), an international program designed to evaluate the agronomic characteristics of maize accessions in Latin American and U.S. germplasm banks for future use, provides useful starting materials. LAMP was based on the cooperative efforts of 12 countries. In a two‐stage evaluation, the project identified the highest‐yielding open‐pollinated top 20% of populations, then approximately the top 5% of those 20%. Twenty of the populations from four countries with temperate climates were randomly selected for fatty acid analysis. The populations were from United States, Chile, Argentina, and Uruguay. Fifty S1 lines from each population were randomly chosen for analysis for a total of 1,000 genotypes sampled. Statistical differences in fatty acid composition were computed among the 20 populations and among the four countries. The findings showed a wide range of fatty acid profiles present in unadapted, elite corn breeding materials with ranges for each fatty acid as follows: palmitic acid, 6.3–18.2%; stearic acid, 0.9–4.5%; oleic acid, 18.5–46.1%; linoleic acid, 36.6–66.8%; linolenic acid, 0.0–2.0%; and arachidic acid, 0.0–1.4%. Several populations were significantly different from the others. Some lines had unusual fatty acid compositions, including one with 8.3% total saturates and another with 20.2% total saturates. This study shows that existing corn breeding materials could be used to produce high‐ and low‐saturate oils, but other methods would probably be required to produce a high‐oleic corn oil.

Evaluation of Peruvian Maize for Resistance to European Corn Borer (Lepidoptera: Pyralidae) Leaf Feeding and Ovipositional Preference

Partial control of the European corn borer, Ostrinia nubilalis (Hubner), in maize, Zea mays L., has been achieved through germplasm resistant to leaf feeding that was incorporated into breeding populations. Leaf-feeding resistance to European corn borer in maize had generally been attributed to presence of the chemical 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA). New sources of resistance, other than that mediated by DIMBOA, are desirable for developing new resistant cultivars. From 1990 to 1992, 1,601 accessions of Peruvian maize maintained in the U.S. National Plant Germplasm System were evaluated for leaf-feeding resistance to European corn borer. Eleven resistant accessions were identified, all of which originated from Peru's north coast. The 11 resistant accessions were then analyzed for 6-methoxybenzoxazolinone (MBOA), the degradation product of DIMBOA and an indicator of DIMBOA levels present in the plant. All 11 resistant accessions contained low MBOA concentrations, equivalent to that found in the susceptible inbred WF9, indicating that DIMBOA is not the basis of this resistance. The factor(s) underlying this source of host plant resistance remains to be determined. Six morphologically diverse Peruvian maize races were evaluated in the greenhouse for ovipositional nonpreference by the European corn borer. Some differences were noted, but morphological factors could not be confirmed as causing the differences.

Evaluation of Pure Red Pericarp and Eight Selected Maize Accessions for Resistance to Corn Ear worm (Lepidoptera: Noctuidae) Silk Feeding

New sources of com ear worm, Helicoverpa zea (Baddie), silk feeding resistance art' needed to protect the maize, Zea mays L., crop without increasing the use of pesticides. Previous evaluation of popcorn germ plasm with red peri carp color showed a high incidence of resistance. Within the National Plant Germ plasm System, there are 15 maize accessions with pure red peri carp color. These 15 accessions were grown in the field at Ames, lA, and Tifton, GA. Fresh silks were collected, dried, and incorporated into a standard pinto bean diet for rearing corn ear worms. Diets were infested with neonates, and the larvae were weighed after 8 d. Results of the diet testing identified four plant introduction accessions that produced 8-d larval weights equal to the resistant control, ‘Zapalote Chico’. The 15 accessions were analyzed for the presence of maysin, three of its analogues, and chlorogenic acid. One accession, PI 245138, had low levels of maysin but was resistant. In addition, eight maize accessions acquired by the National Plant Germ plasm System from 1948 to 1951 were evaluated for corn ear worm silk feeding resistance at Ames and Tifton. One accession, PI 172.328, was rated resistant at both locations.

Combining Ability of Tropical Maize Accessions with U.S. Germplasm

To supplement minimal information regarding the utility of tropical maize (Zea mays L.) germplasm to temperate maize breeding programs, agronomic evaluations of typical accessions of the Latin American races were made. Based on data from previous evaluation stages, 40 accessions exhibiting superior agronomic performance in tropical environments were chosen for photoperiod conversion and combining ability evaluations with U.S. germplasm in temperate environments. Accessions were converted to photoperiod insensitive semiexotic populations by crossing each to Mo44, a temperate‐adapted inbred unrelated to either of two major U.S. heterotic groups. Four families from each semiexotic population were crossed to two U.S. testers. Testcrosses were evaluated in three North Carolina locations for 2 yr. Based on these results, 29 agronomically superior semiexotic testcrosses were tested a third year. The variation for combining ability for yield was estimated to be two times greater among vs. within accessions, suggesting that sampling among accessions be given priority compared with sampling within to maximize genetic diversity for combining ability. Family yields were highly correlated across testers (r = 0.78), suggesting that a single temperate tester would be sufficient for evaluating large samples of Latin American accessions. Grain yields, resistance to gray leaf spot disease (incited by Cercospora zeae‐maydis Tehon & E.Y. Daniels), and other agronomic traits of superior semiexotic testcrosses were competitive with the public U.S. hybrid Mo17 × B73. The best accessions should be a promising source of useful genes for commercial U.S. maize breeding programs.

Evaluation of Cateto Maize Accessions for Grain Yield and Other Agronomic Traits in Temperate and Tropical Environments

The temperate maize (Zea mays L.) race Cateto may have potential for improving grain quality in temperate breeding programs. Temperate germplasm may also be useful in tropical breeding programs for improving yield, agronomic traits, and grain quality. The objective of our study was to assess the yield potential of Cateto race accessions testcrossed with two Corn Belt inbreds for grain yield and other agronomic traits in both temperate and tropical environments. Exotic inbreds representing Cateto, intermediate, and non‐Cateto races were crossed to two U.S. Corn Belt inbreds (Mo17 and B73). Testcrosses (F1s), their F2 and backcross generations, and four checks were evaluated in 1989 through 1991 at three temperate (two in Iowa and one in Missouri) and two tropical (Florida and Zimbabwe) locations. Data were recorded for grain yield, harvest moisture content, days to tassel, ear height, stalk lodging, and root lodging. The testcross‐by‐generation interaction was significant for all traits, except grain yield, whereas the testcross‐by‐tester interaction was significant for ear height, stalk lodging, and root lodging. B73 contributed more favorable alleles for improved standability and grain yield than did Mo17. Although the testcross by location interaction was significant for all traits, the tropical and temperate environments ranked testcrosses similarly. The tropical locations had both the highest and the lowest mean grain yields. The best testcrosses identified in temperate locations may have potential for introgression in the tropics.