Naked, or hull-less, barley is gaining increased interest for human consumption because of its free-threshing habit (lowering processing costs and avoiding loss of bran during pearling) and higher -glucan (soluble fibre) content, implicated in lowering glycaemic index. The naked seed trait is coded by a single recessive gene, nud, where the palea and lemma do not adhere to the caryopsis. However, a persistent problem with naked barley is poor establishment in typical British cool, damp late winter sowing conditions. It was hypothesized that this was due to short coleoptile length in the few European varieties that possess the naked seed trait (most European barleys being hulled). However, the naked trait is widespread in those nations where barley forms a significant component of human diet such as Ethiopia and Central Asia, but where growing conditions are often harsh.
Germination and establishment characteristics of several lines from these areas were tested in the field, cold room and glasshouse. Coleoptile length was found to vary significantly between genotypes and was correlated with successful establishment. However, many exotic genotypes have agronomic traits which are poorly adapted to British growing conditions, such as low disease resistance, unduly short or long duration, lax leaf habit and weak straw. The genotype with the longest coleoptile length, Tibet-37, was crossed with Taiga, a cultivar from Germany which has a short coleoptile and poor field establishment. From this cross a mappingpopulation was produced using the single seed descent method by uni-culm micro plant. 145 recombinant inbred lines (RILs) were produced from which 68 were black, 47 grey and 30 were white seeded. Among these black colour and grey colour lines were true hybrids. However, white testa lines were doubtful; their performance was similar to the Taiga parent. Coleoptile length was found to be heritable in the progeny. Using the rapid micro-plant technique, it was possible to advance to the F6generation within two years. F7 RILs were XVIIIphenotyped in the glasshouse as a first stage in genetic mapping, and the F8 RILs were field tested for coleoptile length and seedling emergence characteristics. Results show that coleoptile length is a continuously variable trait with Tibet-37 and Taiga at the upper and lower ends of the range, respectively. CL showed significant correlation between field and cold room experiment. Seed colour was significantly associated with CL, EP and SE. The black testa colour RILs showed highestCL length hence, it is concluded that black seed colour might be linked with long coleoptile traits and a good morphological marker for coleoptile length and establishment in this population.