Characterization Of Malt Barley Quality And Their Responses To Timing Of N Fertilizer Application

This research was conducted to determine the dynamics of β-glucan content and β-amylase activity of barley varieties during kernel development and their relationships with some characters. Meanwhile, the effects of timing of N application with a same rate on grain and malt qualities of barley were also studied. In these experiments, the dynamics of β-glucan content of two barley varieties during kernel development and the effect of some weather factors on P-glucan content were examined. In addition, grain β-amylase activity and protein content of188barley genotypes with different row-types were determined and the dynamics of β-amylase activity during grain development was measured. The main results are as follows:1. The model of P-glucan content dynamic during kernel development is very similar in both barley varieties, but differs greatly between years. The dynamic of β-glucan content during kernel development is completely consistent with those of kernel-weight increase and protein accumulation per grain. The dynamic of β-glucan content in barley kernel is significantly influenced by the weather factors, and there is significantly negative relationship between accumulated temperature during kernel development and P-glucan content in kernel.2. There was a wide large variation in grainβ-amylase activity among varieties with the same row type, and six-rowed type had the highest coefficient of variation among three types of genotypes. The β-amylase activity in most of major barely varieties ranged from of500U/g to1500U/g, and on average of all varieties with same row type, two-rowed barleys had the highest β-amylase activity. Highly significant positive correlation between β-amylase activity and protein content was found for two-rowed barleys, but not for four-and six-rowed barleys. Eight elite varieties with β-amylase activity above1500U/g and protein content below11.5%were identified from two-rowed barleys. P-amylase activity showed more rapid increase at early and late grain-filling stage than at medium stage, and the highest activity occurred just at maturity stage. In addition, β-amylase activity was significantly and positively correlated with protein content in the grains during grain development.3. Grain protein content was significant higher in the treatment N3(all top-dressed N fertilizer was applied at booting stage) than those in other two treatments, N1(all N was applied at two-leaf age stage) and N2(all N fertilizer was equally applied at two-leaf stage and booting stage), and the two cultivars showed the different response to timing of N application, being significant difference for92-11and no difference for Xiumai3between N2and N3. The effect of N treatments on grain β-glucan content also varied with cultivars, with no significant difference among three N treatments for Xuimai3. Grain β-amylase activity and protein content was significant higher in treatments N3and N2than in N1. Grain (3-amylase activity and protein content were increased with increased the ratio of N application at booting stage. There was significantly positive correlation between grain β-amylase activity and protein content. Grain weight was decreased with increased the ratio of N application at booting stage. The grainp-glucan content of92-11was increased with increased the ratio of N application at booting stage, but the grainβ-glucan content of Xiumai3was not sensitive for N application at later stage. Each trait of grain quality was variable between years. There were the highest malt β-glucanase activities for the two barley cultivars in N2, and the difference from other N treatments was significant for Xuimai3, but no difference was detected between N2and N3. After malting, malt β-glucan content was dramatically reduced in comparison with grain β-glucan content, and the reduction was N treatment-and cultivar-dependant. The greatest reduction happened in the treatment N2for the two cultivars, and Xuimai3showed significantly more reduction than92-11. It is suggested that malt β-glucanase activity play the more important role than grain P-glucan content in the determination of malt P-glucan content. The timing of N application had the dramatic influence on malt quality. In the treatment N3, there were significant lower malt extract and kolbach index, but higher diastatic power relative to those in two other N treatments.