Plant Viruses Assignment Notes

ASSIGNMENT ON INTRODUCTION TO PLANT VIRUSES INTRODUCTION:- →plant viruses are viruses that affect plants. Wke all other Viruses, plant viruses are obligate intracellular parasites that do not have the molecular machinery to replicate, without a host →plant viruses are pathogenic to higher plants. They can cause a dramatic decrease in yield, quality and shelf life and even plant death. →plant viruses are made up of a strand of nucleic acid (DNA COM RNA) Sunounded by protein Sheath. →Technically they are not living, as they are hot-cell based so cannot move or replicate by themselves. There is no cure for plant viruses, they must be managed with cultural practices and virus resistant Plant Stocks. →Head →Nucleic acid → Collar Tail Fiber →Sheath →Base plate Structure:- CMV is a linear positive-sense, Single stranded RNA Virus- It consists of three spherical particles cach approximately 28 m indiameter, one particle containing PNA I, another containing RNA 2, third have RNA 3. Each RNA molecule is enclosed within a protective protein coat- Virus transmission:- →The virus is transmitted by 60 species of aphids, by seeds & dock-der. →Aphids transmit the virus in non-persistant manner. →common sp are- Aphis gossypil, Aphis craccivora, Myzus sp. Symptoms:- →Infected plants show copping of leaves downward. →Yellow mottling & leaf distortion. →Stunting of plants, Shortened Internade & petioles. Gives bushy growth to plants. →fruits are covered with bumpy protusion →Severely affected cucumber fruit may be almost entirely white, which is called as white pickle. protusions yellow Mottling BARLEY YELLOW DWARF VIRUS →The Viruses that cause BYD are typically 25-28 nm in diame-ter and hexagonal in outline. →They are composed of two proteins (a major coat protein && minor read through" protein) that encapsulate the single stian-ded ribonucleic acid (SS RNA) genome. This RNA genome serves as a messenger RNA & has five to 6 genes or open reading frames. →Some proteins are produced directly from the ORFs of the genomic RNA, White Others are expressed from shorter RNAS. Called Suogenomic RNAS. →The viruses that cause BYD are restricted to the phloem of host plants. →They are Seen via electron microscopy in the cytoplasm nuclei & vacuoles of infected Sieve elements, companion & pavenchyma cells. →vesicles containing filaments and inclusions containing virus particles are common cytopathological effects of virus infection →The infection and subsequent death of phloem cells inhib-its translomtion, slows plant growth & induces lass of chlorophyli, resulting in typical Symptoms. Symptoms: The most common Symptom is st ade length. stunting due to reduced intern- →Root mass of infected plants is also often reduced. →The most conspicuous symptom on infected hosts, loss of green colour in leaves is often mote prominent on olles leaves. →Discoloration typically begins in I to 3 weeks after infection & may be preceded by the development of water-soaked areas on the leaves. →Water Soaking Symptoms. TOMATO SPOTTED WILT VIRUS:- Tomato spotted wilt Virus is the type member of the genus Tospovirus in the family Bunyaviridae. →Virus particles que roughly isometric, 80-90 nm in diameter, envolped in a lipoprotein membrane, contain 3 single stran-ded linear RNAs, one of negative & two of ambisense polasi ty, associated with a nucleoprotein to form the nucleacapsid. →TSWV is transmitted by thrips in a circulative & propaga-tive manner →It can effect huntereds of species in 70 botanical families. Symptoms:- →Symptoms may vary widely depending on Variety & enviro-nmental conditions. → Generally leaves become spotted & bronzed in appearance. →plant may droop of writ →fruits develop concentric rings which are light in color & become necrotic. Concentric Spots. 8 X References:- →Alice D & Jeyalakshmi C, 2014, Hand book on introdu-Ctory plant pathology, A. E publishers, coim batore. → Mehrotra RS & Ashok Agarwal, Fundamentals of Plant pathology, Mc Graw Hill Education private limited New Delhi, pp 348-351- →Google images......ا