KETAHANAN POPULASI VARIETAS BAWANG MERAH TERHADAP EPIDEMI PENYAKIT BERCAK UNGU (Alternaria porii) DI DAERAH BATU MALANG

Purple blotch, caused by Alternaria porri is the most severe disease of shallot worldwide. Controlling purple blotch epidemics is difficult, and resistance of host cultivars is either not effective enough, or too easily overcome by the pathogen to be used alone Based on the field trials conducted for one year under natural epidemic, purple blotch severity was significantly lower in cultivar mixture than in unmixed plot of susceptible cultivar alone. Mixtures of cultivars reduced disease progress rates and sometimes delayed disease onset over unmixed plots. This suggests that reduction of area under the disease progress curve (AUDPC) in mixtures resulted from the cumulative action minor effects. Cultivar mixture significantly reduced polycyclic epidemics in shallot plant attacked by A. porri, naturally