Changes of Gramine Contents as an Aphid Resistant Substance with Barley Growth

Barley plants may be severely damaged by aphids,mainly because they may transmit viruses,suck food and disrupt tissues. There are resistant lines and susceptible lines in barley to aphids. The changing amounts of gramine from seeding to mature stages were investigated on 27 lines from 1989 to 1991. Barley was sown aound November 20 in the year and harvested in early June. Higher amount of gramine in seeding stage in all lines were detected,then gradually decreased with barley growth until 2 to 3 weeks before the earing stages. At this time aphids had appeared on the barley leaves and increased in population. The susceptible lines had a tendency of greater decrease in gramine content than the resistant lines at the time of aphid population growth. The maximum aphid population was observed from the end of April to early May. The gramine content was almost constant this time. The degradation mechanisms may be important factors determining the defference of resistant and susceptible lines at the aphid population growth stage. The susceptible lines may have a higher activity of degradation mechanism.