Sclerospora graminicola- and arachidonic acid-induced autofluorescence in downy mildew resistant and susceptible genotypes of pearl millet

Autofluorescence of downy mildew resistant and susceptible cells of pearl m illet seedlings undergoing hypersensitive reaction (HR) upon Sclerospora gr aminicola-inoculation and arachidonic acid (AA)-treatment was studied. Two- day-old seedlings of a highly resistant (IP 18296) and a highly susceptible (23D(2)B) genotype of pearl miller were either inoculated with zoospore su spension of S. graminicola or treated with AA for 24 h. The coleoptiles wit h hypersensitive necrotic spots were processed by the standard procedure, a nd the tissues were subjected to fluorescence microscopy. A differential ac cumulation of autofluorescent compounds in resistant and susceptible pearl millet genotypes was observed with most accumulation occurring in resistant cells treated with AA. The variation in the degree of fluorescence and the spatial accumulation of autofluorescent compounds among the two inoculated /treated genotypes is discussed.