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Johnson, D.L. and M.N. Jha. 1993. Blue corn. p. 228-230. In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York.

Blue Corn

Duane L. Johnson and Mitra N. Jha

  6. Table 1
  7. Table 2
  8. Fig. 1
  9. Fig. 2

Blue corn or maize (Zea mays L.) is an open pollinated flour corn and contains soft starch useful in the milling of specialty foods. Currently, these foods include tortillas, pancake mixes, cornbread mixes, corn chips, and cereal. Experimental extrusion of blue corn has been successful, and extruded blue corn products are now being marketed (Arrowhead Mills pers. commun.). Studies at Colorado State University indicate that the protein content of commercial blue corn is consistantly 30% higher than dent corns in adjacent fields (Johnson and Croissant 1990).

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.


Maize, has been closely associated with the culture and life of the Southwestern American Indian. This paper focuses on a maize of the Hopi Indian, one of the most adaptive of the American Indian tribes. Their culture has been predominantly agricultural throughout their long history in the arid southwest and they have established a reputation as superior dryland farmers (Carter and Anderson 1945). The conservation of their farms is reflected in their crop plants--most notably in their maize. Maize is utilized in ritual as well as a food source. The use of maize in the rituals appears to have preserved these ancient cultivars. Foreign cultures have impacted the Hopi just as they have other cultures in this region. Many of the cultivars of maize grown a century ago by the Hopi are now believed to be extinct while others show an introgression of genes from other maize populations. The number of blue corn races is unknown at this time.


Blue corn planted in non-irrigated conditions has yielded 1,020 to 3,360 kg/ha with market prices of approximately $0.33 to $0.35/kg paid during the last two years. Hybrid development is ongoing, but open pollinated cultivars are currently the only material available for commercial use.

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).


Production practices of blue corn will require modification of those used on conventional yellow dent corn. The seed is planted 4 to 6 mm deep in good moisture at the rate of 20 to 30 kg/ha in dryland (425 mm precipitation) environments. This will provide a final stand of 30,000 to 45,000 plants/ha. Under dryland conditions, seed must be planted into soil moisture. If high production levels are attempted using conventional high soil fertility and additional irrigation water management techniques, severe lodging may be expected. To keep plant height to a minimum, it is advantageous to stress the plants both with low soil nutrition and water until the 12 leaf stage. If irrigated prior to that time, farm experience shows burial of the culm to the last emerged leaf to be effective in reducing lodging and for weed control. All blue corn is open pollinated, therefore uniform field growth, plant size, maturity, and resistance to insect diseases that we experience with hybrid corn should not be expected.

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.


Western corn rootworms may be a problem on fields where corn follows corn in the rotation on hardland soils. Blue corn planted on fallow, following crops other than corn or that planted on sandy soil should escape attack by the Western corn rootworm (Diabrotica virgifera LeConte). Current cultivars of blue corn are very susceptible to European Corn Borer (Ostrinia nubilalis Hubner). In 1991, interplanting rows of amaranth with blue corn in Rocky Ford, Colorado reduced borer damage in the blue corn when compared to borer damage of surrounding dent corn. Stalk rot, (Fusarium spp.) a disease of the lower stalk may cause severe lodging. Lodging may be controlled to some degree by keeping plant height to a minimum or by burial.

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.


Table 1. Analysis of racial variances in New Mexico and Colorado Hopi flour corns for eight traits.

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 ***
Probabilities are reported as ***(P = 0.001)

Table 2. Description of a New Mexico Hopi corn population grown in Colorado.

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

Fig. 1. Blue corn sales by one United States company.

Fig. 2. Row number and ear length of Hopi blue corn populations.
Last update September 10, 1997 aw