Hemp (Cannabis sativa L.) Interruption Cultivation Evidently Decreases the Anthracnose in the Succeeding Crop Chilli (Capsicum annuum L.)

Abstract

Continuous cropping increases disease severity and causes arrested development of chilli plants and the decrease of yield and quality. Hemp-chilli rotation cropping evidently eased chilli diseases, but the causation remains unknown. This paper investigated the disease index (DI) of chilli’s anthracnose for hemp-chilli and continuous chilli cropping, the antifungal effect of water extract of hemp and chilli residues, and bacteria antagonistic to chilli anthracnose fungus from hemp and chilli rhizosphere. Hemp grown as a preceding crop decreased anthracnose DI from 35–39% for the continuous chilli to 14–15% for hemp-chilli rotation. Hemp residue water extract executed suppression of chilli anthracnose fungus and the efficiency increased as the extract concentration increased from 1% to 5%. Hemp extract concentration 5% gave a mean inhibition ratio (IR) of 32.34% to spore germination and IR 53.72% to mycelia growth, which was much greater than that of the chilli extract. Antagonistic bacteria isolated from the hemp rhizosphere evidently depressed the mycelia growth of the fungus with a mean IR 32.35%, while no antagonistic bacteria were obtained from the chilli rhizosphere. The stronger allelopathy of preceding hemp plants and antagonistic bacteria from the hemp rhizosphere synergistically suppressed the fungus growth and eased the disease in the succeeding chilli crop.