Class Tutorial B.Sc(Botany)Part-I Life cycle of Alternaria Dr. Devanand kumar Department of Botany B.N college, Patna University, Patna Life cycle of Alternaria ➢Systemic Position- ▪ Kingdom-Fungi ▪ Division-Ascomycota ▪ Class-Dothideomycetes ▪ Order-Pleosporales ▪ Family-Pleosporaceae ▪ Genus-Alternaria Life cycle of Alternaria ➢Habit and Habitat- ▪ The genus contains about 50 species. ▪ Mostly saprophytes on dead and decaying plant parts and also in soil. ▪ Some species are parasitic on plants. ▪ Alternaria solani causes early blight of potato and other members of family solanaceae. Life cycle of Alternaria ➢Symptoms- • Alternaria shows symptoms of blight. • Early symptoms appear on the leaf as yellowish brown spots or as large concentric rings. • Badly damaged lamina, petiole, stem and tubers can be noticed in severe infection. • Edible parts of tuber turn brown Life cycle of Alternaria ➢Vegetative Structure- ▪ The mycelium is endophytic, profusely branched and septate. ▪ In parasitic species, it is both intra and intercellular, geniculate, light brown and without haustoria. ▪ Hyphal cells are multinucleate. Life cycle of Alternaria ➢Reproduction- ▪ Alternarias have no sexual or perfect stage. ▪ They reproduce asexually by exogenously produced conidia by conidiophore ▪ The conidiophores are short, dark coloured, aerial, septate structures and cannot be easily distinguished from the somatic hyphae. ▪ A conidium develops as an apical bud from the uppermost cell of the conidiophore. Life cycle of Alternaria • The young conidium first divides by transverse septa and some of its cells divide by longitudinal septa. • Conidia with transverse and longitudinal septa are called ‘muriform or dictyospores • In the presence of moisture and suitable temperature each conidium germinates by producing 5-10 germ tubes at a time. • The germ tubes infect the host plant through stomata or, epidermal cells or injuries caused by insects. Life cycle of Alternaria References • www.slm.ignou.com/biology • www.diologydiscussion.com/fungi.