Induced Disease Resistance and Promotion of Shallot Growth by Bacillus velezensis B-27.

Abstract

Shallot is a vegetable crop with high economic value, but its productivity is still relatively low due to various limitations. One of the most hampering factors is moler disease and purple blotch disease caused by Fusarium sp. and Alternaria porri, respectively. Numerous efforts have been made to control these diseases either using chemical fungicides or through improvement of resistant cultivar. This study aimed to determine moler and purple disease suppression and improvement of plant growth by Bacillus as Plant Growth Promoting Rhizobacteria (PGPR) on shallot. Molecular identification of Bacillus was performed by partial gyrB gene sequencing using universal gyrB-F/gyrB-R primers. Field observation and experiments were performed using completely randomized factorial block design single factor with 3 blocks for replication. The partial gyrB gene sequences showed high similarity between Bacillus isolate B-27 and Bacillus velezensis. The application of Bacillus isolate B-27 to shallots was shown to reduce the intensity of moler and purple blotch diseases by 67%. On top of that, Bacillus isolate B-27 increased the plant height up to 27.12 cm, the number of leaves up to 23 blades, tillers up to 8 bulbs and the tuber weight during harvest time up to 33.64 kg. Molecular identification based on partial gyrB gene sequence analysis suggested that Bacillus isolate B-27 has close relationship with Bacillus velezensis. Besides, the application of Bacillus isolate B-27 on shallot could reduce the disease intensity and increase height, number of tillers and plant yield significantly.