Incidence

Dry seed examination of 103 samples of chilli (Capsicum sp.) collected from 16 districts of Rajasthan revealed asymptomatic (06.25-94.25%), moderately discoloured (01.75-42%) and shrivelled-discoloured (01.25-27.75%) seeds in 103, 101 and 100 seed samples, respectively. The discolorations varied from cream to purple-brown spots, water-soaked translucent areas which yielded colonies of Xanthomonas axonopodis pv. vesicatoria on incubation. The standard cultural, biochemical and pathogenecity tests were carried out for identification of the bacterium. The isolates were gram's negative, KOH solubility test positive, levan negative, lipase activity positive, Kovac’s oxidase negative or weak, nitrates were not denitrified or reduced but catalase positive, starch hydrolyzing, gelatin liquefying, hypersensitivity on tobacco leaves after infiltration. Out of 103seed samples, 85 (82.52%) seed samples of 16 districts of Rajasthan revealed 10-100% incidence of the pathogen on Tween-80 medium. The seed-borne inoculum caused pre- and post- emergence losses and symptoms of browning of radicle, splitting of plumule; necrotic spots with bacterial oozing and bright in cotyledonary leaves.

Total seventy five seed samples of brinjal (Solanum melongena L.) collected from major areas of Jaipur districts of Rajasthan revealed 10-100% incidence of Ralstonia solanacearum (RS) on semi-selective TZC Agar medium. For the study all the seed samples were categorised into asymptomatic, shrivelled discoloured and heavily discoloured seeds. Dry seed examination of these samples revealed asymptomatic (07.75-97.5%), shrivelled discoloured (04.50-67.50%) and heavily discoloured (03.25-34.75%) seeds. Two naturally infected seed samples of brinjal carrying 100% incidence of RS were selected for histopathological studies. The heavily infected seeds were with or without epidermal appendages and with water-soaked symptoms. On bisecting such seeds the embryo and endosperm showed necrosis and browning. The pathogen was found confined to the outer seed coat layer particularly at funiculus in the asymptomatic seeds. In shrivelled discoloured seeds of brinjal it was found in seed coat, space in between seed coat and endosperm. It colonised in all the seed components including embryo and endosperm in heavily discoloured seeds. The pathogen caused necrosis, formation of lytic cavities, reduction in cell contents and aggregation of the bacterial cells. The pathogen was found extra- as well as intra embryonal.

For the study of incidence and transmission of diseases of brinjal, a survey was conducted in various fields and market. Dry seed examination of 110 seed samples of brinjal (Solanum melongena L.) collected from 10 districts of Rajasthan revealed asymptomatic (07.75-97.50%), moderately discoloured (02.50-78.50%) and shriveled discoloured (04.25-95.50%) seed samples were studied. The discolouration varied from yellow to brown and black spots on seeds which yielded colonies of Xanthomonas axonopodis pv. vesicatoria on incubation. The standard cultural, biochemical and pathogenicity tests were carried out for identification of the bacterium.