PATHOLOGY THINGS

Tutorial : Preparing slide from fungal like and lower fungi B. Plant disease specimens. Downy mildew of cucurbits Disease symptom 1. Club root disease Development of disease - The single zoospore produced from resting spores penetrates root hairs and there develops into a plasmodium. After a few days, the plasmodium cleaves into multinucleate portions and each develops into zoospore. The zoospore are discharge outside the host through pore dissolved in the host cell wall. Some zoospore  fuse in pairs to produce zygotes,which can cause new infections and produce new plasmodium. These zoospores penetrate young root tissues diretly, whereas older, thickened roots and underground stems are penetrate through wounds. From thesse points of primary infections the plasmodium spreads to corticl cells and the cambium by direct penetration.when it reaches the cambium, the plasmodium spread in all directions in the cambium, outward into the cortex and inward toward the xylem

Field diagnosis : Procedures 1. Compare symptom and hosts with past records In this practical , our group using the following hosts and symptoms : Rhapis excelsa ,  necrosis disease non-infected host  infected host  Cucurbits host, necrosis disease non-infected host infected host    Mosaic disease non-infected host (left) and infected host (right) Necrosis disease non - infected host infected host 2. Identification of pathogens Isolate and make pure culture of the pathogen  1) Cucurbits host - necrosis disease 2) Necrosis disease 3) Rhapis excelsa - necrosis disease 4) Mosaic disease

Exercise 1 Tutorial : Preparing slide from fungal culture General Necrosis   Soft rot Host: Brassicae Pathogen: Erwinia carotovora Blast Host: Paddy Pathogen: Pyricularia oryzae Exercise 3 Koch Postulate.

INTRODUCTION  Plant viruses, as obligate parasites of host plants, can cause extreme injury to plants. They contain nucleic acid (ribonucleic acid [RNA] or deoxyribonucleic acid [DNA]) and a protein capsid. Viruses can be classified on the basis of their chemical compounds and morphology , biologic, pathologic, and molecular characteristics. Viruses can penetrate a host plant cell only in a passive way, through a microscab or with the help of different vectors, such as insects. The majority of plant viruses have a broad range of hosts (e.g.  Cucumber mosaic virus  [CMV],  Tomato spotted wilt virus  [TSWV]), whereas others have a narrower host range (e.g.  Sowbane mosaic virus  [SoMV]). Viral infections can be identified on the basis of the symptoms appearing on test plants (for more exact and qualitative identification, other methods, such as serologic and molecular ones, are necessary. AIM  1) To study the virus morphology 2) To determine the disease symptoms caused by