DETECTION OF RATOON STUNTING DISEASE (RSD) BACTERIUM BY ELISA

Abstract

Ratoon stunting disease (RSD) caused by the bacterium Clavibactor xyll subsp. xyli display limited symptoms on the diseased stalks and no symptoms are noticed in the root or foliar region. An indirect enzyme linked immunosorbent assay (ELISA) technique was standardised to detect the RSD bacterial infection in sugarcane. Bacterial ooze/diffusates from the infected stalk tissues were used as antigen in the assay. Antiserum dilution of 1:1000 and enzyme conjugate dilution of 1:8000 were found optimum for the detection of the RSD bacterium in ELISA. In general the sugarcane varieties showed variation in the bacterium titer. All the varieties showing apparent disease symptoms have shown positive reaction for ELISA and many clones which were not showing any conspicuous symptoms also proved positive by ELISA. Varieties like Co 421, Co 997, Q 28 and CP 52-68 which are used as indicator hosts for the RSD, showed highest titer for the bacterium. Most of the sugarcane varieties evolved recently have shown negative reaction to the disease as compared to the old varieties. This technique was reliable for the detection of the suspected infection of the bacterium in sugarcane than the visual symptoms expressed by the cultivars, wherein the symptomless carriers might escape the detection and spread the disease.