Introduction

Barley was perhaps the most important cereal of the Classical world and has a history of cultivation extending back some 9000 years in the Near East (1). Although its use as a staple for human consumption has declined in modern times, it continues to be the world's forth major cereal crop overall and has important niche applications such as the production of malt. Barley maintains its status as a major crop in the countries of Northern Europe, and enjoys a uniquely broad distribution of cultivation, from the southern shores of the Mediterranean to the Himalayas, the deep sands of Australia, and as far north as the Arctic circle in Scandinavia. In the 15 EU countries, barley is the second in total area planted and in total yield behind wheat.

Virtually all uses of barley depend upon the grain, whether milled as flour or germinated to produce malt. In turn, the characteristics of the foods, beverages, and non-food products made of the grain depend upon the grain's components, primarily starch, protein, lipid, and (3-glucans.

♦Research by the authors reported herein was funded by Academy of Finland Grant 38053

These accumulate during grain filling, the time following fertilization of the ovule when the storage compounds which will support the growth of the young seedling accumulate. Grain yield, the key to sufficient food production and a long-time breeding goal, is merely the sum of grain-filling activity until the point that the grain dries and ceases growth. Due to its importance to yield and downstream applications, a full understanding of the mechanism and control of grain filling is essential.

The dry weight of mature barley grains is comprised largely of carbohydrate and protein, as seen in Table 1. A mature grain, in addition, contains about 15% water by weight following harvest. The thousand-grain weight for barley is approximately 50 g but varies with the cultivar and number of its rows (6-row barley being lower than 2-row). Yields in variety trials are well correlated with starch content (2) and, in the 15 countries of the EU, averaged 4.6 metric tons (range, 1-6.9) per hectare in 1998.

Table 1

Components of the mature barley grain_

Component % of total by weight

Table 1

Components of the mature barley grain_

weight

Carbohydrates

78 —83

starch

50 — 70

p-D-glucan

3 — 6

arabinoxylans

0 0

Post a comment