Canada is a major producer of malting barley. With more than 9 million acres devoted to barley (30% more than the United States), Canada produced over 536 million bushels in 1994. In contrast with the United States, approximately 50% of total Canadian production is two-row malting barleys, while six-row malting types account for 20%, marking a shift over the past 10 to 15 years from predominantly six-row to two-row malting barleys; the rest is feed. A major reason for this shift is that barley production in Canada greatly exceeds domestic use, resulting in an increased emphasis upon the export of barley and malt -- and two-row is the preferred choice around the world. Typically, over 20% of the Canadian crop is exported annually. The United States and China are major customers.

Mexico ranks in the top 10 beer-producing nations, and the national per capita consumption of beer is increasing; however, the domestic supply of malting barley has declined in recent years. Mexico now imports significant amounts of malt and barley from the United States.

(Sources: American Malting Barley Association [Milwaukee, Wisconsin] and Impulsora Agricola, S.A. De C.V [Mexico City, Mexico].)

The Structure of a single barley floret and bracts (spikelet).

The floral structure of the barley plant is the spike, or, as it is sometimes referred to, the head or ear (6). The spike rests at the tip of each stem, also known as a tiller. Several quality variations between six-and two-row barley are directly attributable to spike morphology, so an understanding of the differences is meaningful.

The central axis of the spike is known as the rachis. The rachis is composed of nodes and internodes, with spikelets that can later develop into kernels attached at the rachis nodes. A barley spikelet comprises an individual floret with surrounding bracts. The barley floret is "perfect," meaning that it contains both male (stamen) and female (pistil) floral components; barley is self-pollinating. Following pollination, the fertilized ovary develops into the embryo (germ) and endosperm of the kernel, while the bracts form the husk of the mature kernel.

In both two- and six-row barley, each individual node of the rachis has three spikelets, but the fertility (or sterility) of the florets differs in each type. In six-row barley, all three spikelets (per rachis node) contain a fertile floret. These florets develop into kernels and thus each rachis node in the mature spike of six-row barley has three kernels. When the rachis is viewed from one side, there appears to be three rows of kernels. Kernels occur at nodes on both sides of the zigzag rachis, however, so it looks like six rows. This is perhaps most easily seen when viewed downward from the top of the spike. In two-row barley, only the central floret is fertile and will develop into a kernel; the lateral spikelets are sterile, leaving alternating single kernels on opposite sides of the rachis, for a total of two rows. Barley has multiple stems (tillers) per plant, with many of the stems producing spikes. Two-row barley plants generally have more spikes per plant, but the number of tillers is greatly influenced by environmental conditions.

An additional characteristic used to distinguish malting barley types is the color of the aleurone (3). The aleurone layer is directly under the husk tissues and largely surrounds the endosperm. It is of extreme importance in malting because it is a major site of enzyme synthesis (7). When certain phenolic pigments are present in the aleurone, they may give the dehusked (pearled) grain a black, violet, purple, blue, or green appearance. It should be noted that these aleurone pigments do not have an easily identified contribution to beer color, but are thought to impact flavor. But again, this impact is not easily quantified.  Absence of pigment results in a white aleurone. Blue aleurone color, which is controlled by a single gene, was once quite common in North American six-row cultivars. In the Canadian grain trade, the blue aleurone trait was once used as a marker to distinguish six-row malting cultivars (blue) from six-row feed cultivars. For the most part, blue aleurone barleys have fallen out of favor with North American brewers, and little blue aleurone is currently produced. All North American two-row barley cultivars have white aleurone.