Traits Of Corn Research Articles

Sweet Corn Variety Trials in Ohio: Recent Top Performers and Suggestions for Future Evaluations

A total of 21 and 28 standard and experimental varieties of yellow and white se- and sh2-type sweet corn (Zea mays) were planted in 1999 and 2000 in Fremont and Wooster, Ohio, which are separated by 193.1 km (120 miles) and contain different soil types. Data are reported here for a subset of these varieties (eight yellow, two white) showing a consistently high level of use in Ohio and planted in both years. Endosperm types were planted in distinct, parallel experiments separated by a minimum of 79.9 m (262 ft) at each site. A randomized complete block design with four replications per variety (V) per location (L) was used, with measures of 13 production- and market-based variables taken from emergence to 48 hours after harvest. Soluble solids 48 hours after harvest were greater at Wooster than Fremont in the sh2 study. Variety had a significant, independent effect on mean plant and ear height in the se and sh2 study, respectively, although further analysis of year × variety (Y × V) and location × variety (L × V) interactions suggested that V affected additional traits. On average, `Tuxedo' (se) and `HMX6383S' (sh2) had superior com-binations of grower- and consumer-oriented traits. However, varieties with the highest levels of percent emergence and marketable yield tended to have lower levels of soluble solids, regardless of endosperm type. Y × V interactions were primarily due to changes in the magnitude of values for individual varieties in each year, not from changes in their relative ranking. The Y × L × V interaction was significant (P ≤ 0.05) for marketable yield, plant and ear height, and the ratio of ear length to diameter in the se study, but zero variables in the sh2 study. Coefficients of determination (R2) for selected plant and ear traits were unaffected by location. Overall, R2 values ranged from 0.04 (number of rows of kernels × ear diameter, sh2 study) to 0.83 (shank length × total ear length, sh2 study). These data reinforce that genetics strongly affect key traits in sweet corn and identify two potential top performers. The data also suggest that independent L or L × V effects may be minor relative to V effects, even when locations are separated by moderate distances and contain different soil types. Therefore, including more varieties but fewer sites may be warranted in future variety trials. The data also suggest that 1) ratings of variety performance should be based on objective measures of grower- and market-oriented traits and 2) shank length × total ear length and ear height × plant height relationships may be used to improve the efficiency of future evaluations.

Heritability estimates for quality and ear traits in sweet corn

The development of cultivars with reduced pericarp thickness, high sugar content and husks covering ear tip will improve the market for Brazilian sweet corn and may open a new market for export. The knowledge of parent-offspring relationship helps to choose a breeding method, to decide selection intensity, and to predict genetic gains for the traits under selection. The objective of this work was to estimate heritability for pericarp thickness, soluble solids content and percent of ear tip in three open-pollinated sweet corn populations - BR400, BR401, and BR402 - using half and full-sib families. Genetic variability was detected for all traits in the evaluated populations. The estimated heritability for pericarp thickness was larger than those estimated for soluble solids content, and percent of ear tip for all populations in this study. As a consequence, the expected genetic gains will be larger for pericarp thickness than for the other traits evaluated in this work.

Comparison of Phenotypic and Marker‐Assisted Selection for Quantitative Traits in Sweet Corn

This investigation was designed to empirically compare the efficiency of marker‐assisted selection (MAS) and phenotypic selection (PS) in enhancing economically important quantitative traits in sweet corn (Zea mays L.). Marker‐assisted selection and PS were applied to three F2:3 base populations (C0) with either the sugary1 (su1), sugary enhancer1 (se1), or shrunken2 (sh2) endosperm mutations. One cycle of selection was applied for both single and multiple traits including seedling emergence, kernel sucrose concentration, kernel tenderness, and hedonic rating (taste panel preference). Twenty percent of the families in each of the base populations were selected and intermated to constitute MAS‐ and PS‐based C1 composite populations. Selection efficiencies were evaluated on the basis of gains over one cycle and estimated evaluation costs. A total of 52 paired comparisons were made between MAS and PS composite populations. In 38% of the paired comparisons, MAS resulted in significantly higher gain than PS across the three C1 composite populations, while PS was significantly greater in only 4% of the cases. The average MAS and PS gain across all composite populations and selected traits, calculated as percent increase or decrease from the randomly selected controls, was 10.9% and 6.1%, respectively. Use of MAS is most appropriate when traits are difficult and costly to measure. However, for some traits, the higher gain from MAS can compensate for the higher costs of MAS. It was concluded that incorporating DNA markers to traditional breeding programs could expedite selection progress and be cost‐effective.

Mechanisms of Corn Tolerance and Velvetleaf Suppressive Ability

AbstractCrops that better tolerate weed competition or preempt resources from weeds may reduce dependence on herbicides for weed control and benefit an integrated weed management program. Irrigated field experiments were conducted to identify morphological traits of corn (Zea mays L.) that enhance its tolerance and weed suppressive ability. Two old (circa 1940) and two modern corn hybrids were grown in mixture with five target densities of velvetleaf (Abutilon theophrasti Medik.) in two years. Corn height and leaf area index (LAI) were measured periodically throughout the growing season. Vertical leaf area distribution was measured at corn anthesis. Quantitative estimates of these traits were obtained for each experimental unit using linear and nonlinear regression analysis. Magnitude of the correlation between these trait estimates and corn yield reduction in mixture with velvetleaf or velvetleaf seed capsule production was used as an indicator of the importance of each trait to the enhancement of corn tolerance or velvetleaf suppressive ability. Canopy traits having highest correlation with corn relative yield in 1995 were maximum LAI (r= −0.38) and crop density (r = −0.24). Those with highest correlation in 1996 were crop density (r = ‐0.36), degree days accumulated between emergence and 50% maximum height (r = 0.34) and LAI (r = 0.19), and vertical leaf area distribution (0.49). Corn canopy traits were not correlated with velvetleaf seed production in 1995. However, vertical leaf area distribution (r = 0.60), maximum LAI (r = −0.32), and corn density (r = −0.26) were correlated with velvetleaf seed production in 1996. Results suggest that increasing maximum corn LAI, rate of canopy closure, or height at which leaf area occurs in the canopy can improve corn tolerance and velvetleaf suppressive ability. These traits can be modified by varying cultural practices such as row spacing and population density, or through breeding.

Contributions of Dent Corn Germplasm to Stalk and Root Quality in Sweet Corn

Root or stalk lodging can be a serious problem in sweet corn (Zea mays L.) production. Four dent corn inbreds, crossed to five sweet corn inbreds in a design II mating system, and a half diallel with five sweet corn inbreds were used to 1) determine the effect and potential contribution of dent corn germplasm on stalk and root quality traits in sweet corn, 2) examine the variation for stalk and root quality traits in some sweet corn germplasm, and 3) evaluate the utility of traits used in improving dent corn root and stalk quality in sweet corn improvement. The dent corn germplasm used in this study had a favorable affect on stalk and root quality in the dent × sweet hybrids. Compared to the sweet × sweet hybrids, the dent × sweet hybrids had significantly higher stalk crushing strength and stalk soluble carbohydrates, while having significantly less stalk lodging. The mean stalk lodging for the dent × sweet hybrids was 4.4%, while the sweet × sweet hybrids averaged 18.7%. Within the diallel, effects due to hybrids were highly significant for stalk section weight, rind thickness, and stalk diameter. Percent stalk lodging was negatively correlated with stalk section weight [r = (-0.63), P ≤ 0.05] and crushing strength [r = (-0.64), P ≤ 0.05]. No traits were significantly correlated with root lodging within the sweet corn crosses. Dent corn has potential as a source of improved stalk and root quality in sweet corn.

Effects of the Sugary‐1 Locus on Plant and Ear Traits in Corn1

Attempts to use dent corn (Zea mays L.) to improve sugary‐1 (su) sweet corn have not been widely successful due to difficulty with the simultaneous recovery of traits being transferred and acceptable quality. The lack of success may be caused by linkage, pleiotropy of the su gene, inadequate recombination before initiating selection, or insufficient population size. The objective of this study was determine if the su allele affects 19 important sweet corn traits. Plants from starchy (Su) and sugary (su) So seed of a dent ✕ sugary composite were grown in four environments at 36 900, 57 400, and 73 800 plants ha−1, with ear measurements recorded at milk‐stage maturity. The Su and su S1 progenies were grown in two environments at 51 700 plants ha−1, with data taken on mature dried ears. Sugary So segregates demonstrated a greater tendency toward delayed maturity and lodging than Su segregates. Tip blanking was reduced in su So and S1 plants. Ear length was reduced in su So plants and Susu plants from Su‐‐S1 ears. Plant endosperm type had no effect on percent marketable ears or yield among So segregates, or on S1 ear diameter, taper, and curvature. The su gene effects provide some explanation for the difficulty encountered when using dent corn in sweet corn improvement, but were not so pronounced as to be insurmountable in a breeding program.

Effects of Population Density upon Agronomic Traits Associated with Genetic Increases in Yield of Zea mays L.1

AbstractSeveral long term recurrent selection programs with strains of Zea mays L., which were initiated from one to three decades ago, are being carried out at plant densities considerably below those currently used in commercial production. The question arises whether responses realized at low plant densities will be maintained at higher plant densities. We chose to study strains from a selection program initiated three decades ago, in which 10 cycles of full‐sib family selection have been completed at a density of 24,000 plants per hectare. A study was conducted to characterize changes in agronomic traits of corn resulting from recurrent selection for yield when evaluated at 24,710, 38,300, and 49,420 plants per hectare. Comparisons were made among the original strain and strains resulting from the fifth (C6) and 10th (C10) selection cycles.The improved strains, C5 and C10, averaged 27 and 42% more yield than the original strain. Important increases in prolificacy, ear corn/stover ratio, and total N accumulation in the grain were found to accompany the increases in yield due to selection. Increased population density resulted in greater yields per hectare in the improved strains. Interactions between strain and density were not statistically significant.Both ear height and top height increased with selection, but leaf size and ear weight appeared to have decreased. Decreases were also noted in percent N in the grain and the stover.

Effects of Recurrent Selection for Crushing Strength on Morphological and Anatomical Stalk Traits in Corn1

Twelve morphological and anatomical traits were evaluated in two synthetics of corn, Zea mays Lo, which had undergone selection for high and low crushing strength. The two synthetics were represented by third cycle selections designated ‘MoSQ A‐High,’ ‘MoSQ A‐Low,’ and ‘MoSQ B‐Low.’ The study was conducted to determine whether selection for stalk strength resulted in corresponding changes in one or more anatomical traits. Most of the traits evaluated were affected by selection. Significant differences, however, were not detected among the four sub‐populations for rind density. Multiple regression coefficients indicated that stalk density and rind density were relatively less important than rind weight and area of rind in predicting rind crushing strength. The area of vascular bundles, the area of lignification, and the we;.ght of rind and stalk section were correlated with rind crushing strength responses to selection.MoSQ A and MoSQ B were similar in stalk strength, but derived their essentially equal strength in different ways. MoSQ A had greater number of vascular bundles than MoSQ B, and vascular bundle number was greater for the high than for low selections. MoSQ B had more lignification per vascular bundle than MoSQ A, and the lignified area in the rind was correlated with crushing strength. We concluded that populations may differ in the particular array of anatomical traits that contribute to stalk strength. Nevertheless, strength in this study appeared to reside principally in the rind tissue.

Interrelationships Among Plant Height, Number of Leaves, and Flowering Dates in Maize1

AbstractWe evaluated the effect of different environments on the interrelationships among three morphological traits in corn (Zea mays L.) to see if relationships observed in limited environments held true over widely different growing conditions.Data on number of days from planting to anthesis, plant height, and number of leaves per plot were obtained from 10 corn strains involving three greenhouse planting dates and 23 strains planted at 20 different locations ranging in latitude from 21° North (Mexico) and 49° North (Canada). The results indicated that although plant height at maturity was highly correlated with number of days from planting to anthesis in a limited range of environments, this relationship was very low when considered over a wider range of environments. In most cases, the relationship between number of leaves at maturity and number of days from planting to anthesis was even lower than that for plant height and number of days from planting to anthesis, especially when considered over wider environmental conditions. A significant correlation existed between plant height and number of leaves for most strains. The degree of relationship among the three characteristics varied among strains.