SummaryAmong the 12 varieties of tea tested against three isolates of Pestalotiopsis theae, causal agent of grey blight disease, Teen Ali‐17/1/54 and TV‐23 were found to be highly susceptible while CP‐1 and TV‐26 were resistant under identical conditions. Leaf antigens were prepared from all the tea varieties, three isolates of P. theae and a non‐pathogen of tea (Bipolaris tetramera). Polyclonal antisera were raised against mycelial suspensions of P. theae (isolate Pt‐2) and leaf antigens of Teen Ali‐17/1/54 and CP‐1. These were compared an immunodiffusion test and enzyme‐linked immunosorbent assay to detect cross reactive antigens (CRA) shared the host and the parasite. CRA were found among the susceptible varieties and isolates of P. theae (Pt‐1, 2 and 3). Such antigens were not detected between isolates of P. theae and resistant varieties, B. tetramera and tea varieties or isolates of P. theae. Indirect staining of antibodies using fluorescein isothiocyanate (FITC) indicated that in cross sections of tea leaves, the CRA was concentrated in the epidermal cells and mesophyll tissues. CRA was present in the young hyphal tips of the mycelia and on the setulae and appendages of the conidia of P. theae.

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Bacterial cankcr, spot, and speck of romatoes (Lycopersicon esculennnn Milir.) caused by Corynebacteriu.tn mi.chi.ganerue (E.F.S.) Jensen, Xanthontonas uesicatoria (Doidge) Dows., and Pseudomonds tolndto (Okabe) Burk., respectively, were symptomatologically differentiated on 2-to 3-week-old spray-inoculated seedlings only under conditions of 87-97% relative humidity tnd 23-28'C temperature. The numerical threshold of infection of both C. mi.chiganense andP. totnato was 1X106 cells/ml and that ol X. vesicatorla u'as 1X103 cells/ml.Preinoculation host injury and an inocuium concentrarion of 1X10" cells/ml 'were most favorable for high incidence of the diseases.Characteristic symptoms incited by the canker organism were (1) small whitish pimpleJike spois developing into'raised blisrerlike lesions on'tire lamina, (2) elongated swellings on veins, and (3) cankers on the hypocoryl. The distinctive symftoms of thE bacterial' spor'dis""r" were (1) small lreenish-yellow to brown leaf spots, (2) large yellow blotches becoming necrotic and producing a severe blight effect on leaves, and (3) light-brown iueaks on the hypocotyl.The distine-uishins symptoms of the'soeci dit."r. were discrere daik-bro*"n spots and irccasioial' mirgina.l necrori; areas on leaves and coryledons. On cotyledols, both C. michiganense a,nd X. vesicatoria produ,ced, identical minute rvhitish flaky spots often-with greenish cenrers. Sometimes rhese spors coalesccd and iesulted in wrinkline of the surface of the cowledon.

Isolates of Xanthomonas phaseoli var. fuscans (Burkh.) Starr & Burkh. obtained from naturally infected bean (Phaseolus vulgaris L.) seeds stored at 10 C for 2–4 months were more virulent, as indicated by a stunting effect on Sanilac bean plants, than isolates obtained from seeds stored for 7–24 months. Neither the rate of growth of the organism nor its ability to produce a brown diffusible pigment was correlated with virulence. Growth rate and pigment production of all isolates in nutrient broth were similar and reached a maximum after 36 and 48 h respectively. In a medium containing inorganic salts and yeast extract, the growth rate of the organism was relatively slow and pigment development depended upon amendments added to the medium. Tyrosine enhanced, while glucose retarded, pigment production, but neither affected the growth of the pathogen adversely. The formation and color of the pigment in the media were not affected by pH values ranging from 5.5 to 9.0. The presence of living cells was essential for the continued production of the pigment. The melanoid nature of the pigment was demonstrated.

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