Irish Famine Essay

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Irish Famine (1845–1849), and still remains the most destructive pathogen of solanaceous crops, including tomato and potato. The soya bean root and stem rot agent, Phytophthora sojae (Anon., 2016e).
e) Macrophomina: It has a very wide host distribution covering most of the tropics and subtropics, extending well into temperate zones (Songa 1995).
f) Fusarium: The fungal pathogen Fusarium oxysporum cause disease to a wide variety of hosts of any age. Tomato, tobacco, legumes, cucurbits, sweet potatoes and banana are a few of the most susceptible plants to this pathogen.
g) Verticillium: Many economically important plants are susceptible including cotton, tomato, potato, brinjal, pepper and ornamentals.
4.2. Bacteria :
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Colonization of a root occurs at fine scales with growth and movement of fungal mycelia through soil. However, epidemics are observed at coarser scales and depend on a cascading spread through populations of roots.
5.1. Factors influencing the soil borne plant pathogens :
a) Moisture: Moisture is of utmost importance for pathogenic fungi and bacteria. Rain splash plays an important role in the dispersal of some fungi and nearly all bacteria, and a period of leaf wetness is necessary for the germination of spores. Propagules germinate in the presence of water and are dispersed. Because the process of germination and infection takes time, the duration of leaf wetness also affects the occurrence of the infection. The duration necessary for infection varies with temperature. Usually, a longer period of leaf wetness is needed to establish an infection in cooler temperatures, as germination and infection are generally accelerated in warmer conditions.
b) Temperature: Temperature affects the incubation or latent period (the time between infection and the appearance of disease symptoms), the generation time (the time between infection and sporulation), and the infectious period (the time during which the pathogen keeps producing propagules). The period of leaf wetness and temperature information is being used to predict outbreaks of diseases (infection periods) and can be helpful in prophylactic
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