Fig. 1. Blue corn sales by one United States company.
Consumption and sales of blue corn is increasing (Fig. 1). The market is in Mexican restaurants, health food stores, and some supermarkets. The term "blue corn" is a generic term with plants producing blue and mixtures of blue and white kernels. Bluecorn sales continue to show growth as shown in Fig. 2.
These maize populations have not been utilized to a great extent in major maize improvement programs and are of value not only historically, but also as germplasm pools for future evaluation. We know that maize landraces are uniquely variable not only from region to region but also from cultivar to cultivar and from plant to plant. For geneticists, such populations provide a stockpile of genes that have rarely been sampled or studied. If these various strains are not preserved, it is inevitable that many of them will be lost to introgression. Furthermore, the germplasm of drought tolerance may reside in the southwestern Indian maizes and this material has not yet been utilized extensively in United States maize improvement programs.
Five Hopi blue flour maize populations were compared to similar populations described in the 1950s by Brown et al. (1952). Two landraces of Southwestern flour maize were obtained from the Talavaya Center (Espanola, New Mexico) and two landraces identified by Krumpacker were provided by Robin Cuany, both from Colorado State University. These maize races had been obtained from local American Indian farmers (New Mexico) and from Hispanic farmers (Colorado). A fifth population was obtained from the Talavaya Center and was identified as "Hopi blue corn." To avoid confusion, this population was referred to as "Hopi blue corn" with other populations having the designation of New Mexico and Colorado blue corn. Variances and covariances between the races of maize indicate significant differences for the traits studied and that these populations do not appear to have a common origin (Table 1). Plant height varied from 1.00 to 1.35 m for both New Mexico and Colorado populations. The Hopi blue corn population differed significantly from the other populations and reached a plant height of 1.8 to 2.4 m. Tillering was observed with eight to ten tillers per plant in the New Mexico and Colorado populations while two to three tillers were seen in the blue corn 1 population. A typical population of New Mexico blue corn is described in Table 2.
The number of rows per ear varied within each New Mexico and Colorado population from 8 to 16 and average 12.3 populations. Row number ranged from 10 to 18 in the Hopi blue corn (Fig. 2). This character is similar to those previously reported by Brown and Anderson (1947). The characteristic 14 row trait noted in Hopi corn was observed in all races but lacked the apparent preponderance noted by Brown et al. (1952). Ear characteristics such as yield, ear length, cob diameter, kernel thickness, and kernel weight are similar to the Hopi corns previously reported. The differences from prior research (Brown and Anderson 1947) were primarily noted to be in the greater width and reduced length of the kernels, greater ear length, reduced number of rows, greater internode length, greater tillering, and a narrowing of the leaf blades. Many of the phenotypic traits observed differed greatly from those of the Mexican dent corns and the Basketmaker corns. We anticipated that these races might have affected introgression into the Hopi corn populations.
In the Colorado and New Mexico populations, ear length and kernel yield were positively correlated in both the New Mexico (r = 0.73) and Colorado (r = 0.76) cultivars. A significant correlation between kernel thickness and cob diameter was observed in all populations. These values when compared to those reported by Brown et al. (1952) were similar to the Hopi corns of the early 1950s with one exception: Brown et al. (1952) showed that blue and white flour corn had a negative correlation between kernel width and kernel thickness. This was not been observed in the Colorado study. Positive correlations for these traits to the purple corn were, however, observed in the study. Path analysis of the five corn populations indicates kernel weight, width of kernel, and thickness of kernel are the most important components of yield in these races of blue corn and each had a positive direct influence on yield.
The Hopi corn ear possesses several characteristics not generally found in more common corn. The most conspicuous is the width of the ear at the shank end which averaged 18.5 mm in these landraces. Several traits showed significant to highly significant differences between the landraces (Table 1). These results are very similar to that of other Hopi corn races as reported by (Brown et al. 1952).
To keep blue corn quality high and prevent cross-pollination of other types, it is recommended to maintain minimum isolation distances of 230 m from other types of corn for seed production. If minimum distances are not adhered to, F1 seed will be blue as the blue color is dominant. Subsequent crosses may show color segregation as well as endosperm variation. Some color variation is normal in currently available cultivars.
As blue corn advances in maturity, the kernels will be white until the drydown period. At this time, the blue color appears and darkens as drydown progresses. Harvest should begin when the grain moisture reaches 18% and should progress rapidly. As kernel moisture declines, lodging increases depending on plant height, amount of stalk rot present, and the incidence of wind. Combine cylinder speeds must be reduced with special efforts to minimize seed cracking. Seedcoat cracking interferes with its removal during processing. Combined grain should be dried with aeration to less than 13% prior to shipping. Commercial operations use popcorn cleaners and baggers for their crops.
Buyers generally require delivered clean grain that is free of disease, insect, and foreign matter. Cracked and broken grain is objectionable and a 5% tolerance is allowed for total defects.
| Variable | MS | F | P | |
| Kernel yield (g) | 16585 | 25.1 | 0.000 | *** |
| Shank diameter (cm) | 164 | 0.9 | 0.349 | NS |
| Ear length (cm) | 15307 | 10.9 | 0.001 | ** |
| Cob diameter (cm) | 168 | 10.1 | 0.002 | ** |
| Kernel width (mm) | 1 | 3.8 | 3.860 | NS |
| Kernel thickness (mm) | 5.6 | 7.7 | 0.006 | ** |
| Row number | 3 | 1.3 | 0.289 | NS |
| Kernel weight (gm) | 602 | 43.3 | 0.000 | *** |
| Variable | Mean | SD | Min. value | Max. value |
| Kernel yield (g) | 53.6 | 17.6 | 32.0 | 98.0 |
| Shank diameter (cm) | 7.4 | 0.3 | 1.0 | 2.6 |
| Ear length (cm) | 15.2 | 3.3 | 9.0 | 21.0 |
| Cob diameter (cm) | 2.9 | 0.4 | 2.2 | 3.8 |
| Kernel width (mm) | 6.7 | 0.7 | 5.0 | 8.0 |
| Kernel thickness (mm) | 4.2 | 2.7 | 3.7 | 4.8 |
| Row number | 12.2 | 1.6 | 8.0 | 16.0 |
| Kernel weight (gm) | 19.1 | 3.3 | 10.5 | 28.9 |
