In this article we will discuss about:- 1. Vegetative Body of Peronospora 2. Reproduction in Peronospora 3. Control Measures for Disease.
Vegetative Body of Peronospora:
The mycelium is typically coenocytic, consisting of much-branched hyphae. These hyphae usually ramify in the intercellular spaces of the host cells. It draws nourishment from the adjustment living cells by means of haustoria.
Reproduction in Peronospora:
Peronospora reproduces both asexually and sexually. At the time of asexual reproduction several conidiophores developed from the intercellular mycelium, emerge through the stomata on the ventral surface of the leaves. Subsequently elongate considerably and bifurcate 6-8 times at the apex and the ultimate branches bear conidia at their tips.
The conidia are usually oval sometimes spherical, hyaline and uninucleate. Eventually these conidia are disseminated by the wind, and when fall on suitable host they germinate under favourable conditions and give rise to germ tubes from indeterminate points on the sides of the conidia. The germ tubes usually enter into the host through the stomata, or direct penetration of the epidermal cells of the host plants.
Sexual reproduction is oogamous. In this case well differentiated antheridia and oogonia are developed from the nearby hyphae.The antheridium is multinucleate in the beginning, but gradually the nuclei except one degenerate.
The remaining nucleus acts as the male nucleus. On the other hand, the oognium is also multinucleate at the early stage but with further development, it becomes differentiated into central uninucleate oosphere and peripheral multinucleate periplasm.
During gametangial contact a fertilization tube is formed by the antheridium which penetrates the periplasm and finally discharges the male nucleus into the oosphere. The male nucleus then fuses with the female nucleus and consequently, a zygote is formed.
After fertilization, the zygote develops a thick wall and after a period of rest inside the host or in the soil, it germinates by producing germ tubes under favourable conditions, and initiates fresh infection. Possibly, the first nuclear division is reductional inside the zygote.
Control Measures for Disease Caused by Peronospora:
The disease may be partially controlled by spraying with chloranil (spergon) and zinc sulphate, and crowding of plants should be avoided.
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