BP Singh

Symptoms of Fungal and Bacterial Diseases 137Xanthomonas c011lpestl'is pv. ph as eo Ii and Pseudomonas syringae pv.phaseolicola produce a bluish-white fluorescence on bean seeds.Symptoms on host-plantLeaf spotSpots are the most common symptoms observed on a widevariety of plant species. Spots start as minute, chlorotic flecks,which later increase in size and become necrotic. Spots may appearin different shapes, sizes and colours like round, elliptic, elongated,oval or irregular and pale, brown, dark brown, reddish to black.Examples: Spindle shaped (Pyricularia onjzae); long stripes(Drechslera graminea), oval, brown with grey centre {Drechsleraoryzae)j circular to slightly angular with grey centre and reddishborder (Cercospora spp.); spots with concentric rings (Alternariaspp.); and water soaked and raised on lower surface and depressedon upper surface (Xanthomonas vesicatoria).Leaf blightBlight implies sudden and extensive damage to leaves.Under favourable conditions, the spot increase in size, coalescewith each other and occupy larger area of the infected leaves. Atthis stage the leaves appear blighted (scorched). Beside leaves,blight appears on stem. Ultimately whole plant may die. Examples:. Early blight of potato (Alternaria solani); late blight of potato(Phytophthora infestans); maize leaf blight (Drechslera maydis);Phyllosticta leaf blight of maize (Phyllosticta maydis); Halo blightof beans (Pseudomonas phaseolicola); Common blight of beans(Xanthomonas phaseoli); Phomopsis blight of egg plant (Phomopsisvexans); Bacterial blight of pea (Pseudomonas pisi); and Ascochytablights of peas (Ascochyta spp.).AnthracnoseThe anthracnose has been used for two distinct types ofdiseases, one producing typical necrotic spot like lesion of deadtissues and the other like raised border around a more or lessdepressed centre. It develops most commonly on the youngsucculent parts of stems, petioles leaves, fruits and rarely on roots.In case of beans, usually the lesions are dark brown, in moistweather, pinkish spore masses can often be seen. Elongated spots.appear on the veins on the lower side of the leaf and later spread