Response of barley varieties to attack by the barley shoot fly (Delia flavibasis) in Kenya
1991
Macharia, M. (NPBRC, Njoro (Kenya))
Field and greenhouse experiments were conducted to determine the effect of attack by the barley shoot fly (Delia flavibasis Stein) on several barley varieties. Significant differences (P less than 0.05) were noted in tillering capacity between infested and control plants under field conditions. For infested plants, shoots developed in an asynchronous manner and spikes matured unevenly. Infested plants were observed to compensate for shoot fly attack by recovery growth. Field observations confirmed that the slow rate of development and the compensatory growth delayed maturity. Greenhouse studies revealed that barley plants infested with D. flavibasis larvae at the 1.1-1.2 growth stages (Zadoks) were virtually killed, while plants infested at stage 1.3 survived. Infested plants suffered a check in growth and development, but recovered later. Also, in response to attack, proportionately more tillers were produced by infested plants than control plants. This suggests tolerance as the mechanism of resistance. Virulence analyses of yellow rust isolates were carried out in Kenya between 1986-1989 and compared with earlier results. Races showed a clear increase in the number of virulence factors. Before 1971, races carried from 3 to 7 virulence factors whereas the dominant races after 1986 were characterized by 10 to 12 virulence factors. Virulence on the resistance genes Yr2, Yr2+, Yr6, Yr6+, Yr7, Yr7+, Yr8, Yr9, Yr9+ and on the cultivars Anza, Strubes Dickkopf and Suwon92/Omar occurred at a high frequency, while no virulence for Yr3, Yr4, Yr5, Carstens V and Spaldings Prolific was found
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