Ex.No. 8                 Life cycle of Peach leaf curl, Powdery mildew and Ergot

                 Host                                 :         Peach        Disease: Peach leaf curl          

                 Causal organism         :        Taphrina deformans (Asexual stage is Lalaria)

Asexual reproduction:

                The pathogen survives as blastospores in the bark and the bud scales. They are haploid in nature. By budding ascospores are multiplied and form primary blastospores (haploid, round/ovoid). It is a “spring time” disease as the primary infections occur in spring. By conjugation, these haploid blastospores are converted into dikaryotic blastospores (secondary blastospores) and they are settled on the host surface. On the surface of the leaf, blastospores on germination produce germ tube that infect the host and form dikaryotic mycelium or dikaryotic ascogenous cell (Dimorphic, Enteroblastic).

Sexual reproduction:

                Each ascogenous cell is converted into ascus (dikaryotic in nature/ through crozier formation). After karyogamy, it becomes diploid ascus. They are produced 8 ascospore are inside the ascus. After the ascospores are released they begin to bud and form numerous blastospores which eventually produce germ tube and infect the host.

            Host: Pulses,        Disease: Powdery mildew/ Sac mildew / White mildew

                Causal organism      :           Erysiphe polygoni

Asexual reproduction:

                Ectophytic mycelium produces globose shaped haustoria and terminally aerial mycelium produces conidiophore which arises vertically from the hyphae. The conidia are disseminated by wind (Anemochory). Few days after infection conidia began to cut off from conidiophore and easily carried by wind. Under favourable conditions conidia germinate and producing germ tube which develops into new ectophytic mycelium.

Sexual reproduction:

                The antheridium (male gametangium) and ascogonium (female gametangium) are formed under favourable conditions.  The antheridium is a stalked structure and lies close to the ascogonium and through the crozier formation the eight ascospores are formed. The asci are finally enclosed by enveloping hyphae forming

a closed fruiting body is called as cleistothecium. Later they germinate to produce germ tube and to form new hyphae. 

            Host                              :            Cumbu              Disease : Ergot / Sugary disease in Cumbu

                Causal organism      :            Claviceps fusiformis (Claviceps microcephala)

 (Ergotamine ; Ergot of Commerce – LSD is obtained from the sclerotia)

Reproduction:

Filiform ascospores are disseminated by wind and they germinate on flowers, infect the ovaries. The conidial stage is Sphacelia. The conidia are hyaline, multiply by budding. At the end of the season, they produce pseudograin type of sclerotia, mushroom shaped stromata.

Sexual fruiting body is Perithecium