VARIETAL DIFFERENCES AND FAMILY ANALYSIS OF THE PERCENTAGE OF HULL-CRACKED GRAINS IN 2-ROWED BARLEY

A total of 48 two-rowed barley varieties with various percentage of hu ll-cracked grains which reduce the germinability of malting barley gra ins, was examined in Kurashiki and Gunma both in 1992 and 1993 with tw o replications. Percentage of hull-cracked grains and thousand kernel weight were recorded (Table 1). Besides, progenitors of Yoshikei 16 an d Nittakei 22, whose hull-cracked grain percentage was extremely high, were examined in Gunma in 1992 and 1993 for analyzing the inheritance of the trait, In the first part of the study, it was demonstrated tha t varietal differences as well as variations due to location and year of cultivation were highly significant; varietal variation of the perc entage of hull-cracked grains ranged from less than 1% to 67%, and the mean percentage was significantly higher in Kurashiki (11.5%) than in Gunma (4.4%), and higher in 1992 (9.2%) than in 1993 (6.8%). The vari ety x location interaction was also statistically significant (Table 2 ). Heritability estimated per plot base was 0.6. Correlation coefficie nts between years and locations were as high as 0.64-0.85 indicating t hat the character expression of the genes concerning the percentage of hull-cracked grains was rather stable over the environmental conditio ns (Table 3). For the thousand kernel weight, variances due to variety , location, year x location, variety x location and variety x year wer e statistically significant (Table 2). Correlation coefficients betwee n gears and locations were slightly lower than those of hull-cracked g rains (Table 4). The thousand kernel weight was larger in Kurashiki (4 4.2 g vs 38.8 g) where the percentage of hull-cracked grains was highe r. Phenotypic correlation coefficient between the percentage of hull-c racked grains and thousand kernel weight ranged from 0.14 to 0.32. Bas ed on the family analysis of Yoshikei 16 and Nittakei 22 for the perce ntage of hull-cracked grains, it was revealed that this trait was not controlled by simple major gene(s), but by the accumulation of multipl e genes controlling its component characters, because none of the prog enitors, except for Nittakei 8, a female parent of Yoshikei 16, showed a high percentage of hull-cracked (Figs. 1 and 2). In addition, no pr ogenitor of Nittakei 8 showed a high percentage. Because the wild two- rowed barley Hordeum spontaneum and local two-rowed varieties do not d evelop hull-cracked grains, while malting barley varieties with higher malt extract and lower husk content tend to develop hull-cracked grai ns, it is assumed that the hull-cracked grain trait may result from in tensive breeding programs aimed at the improvement of the malting dual ity of barley.