Disease resistance, development

Care must be taken with chemical choice especially with the increase in fungicide resistance particularly against septoria, eyespot and mildew. Strobilurins (Qols) should not be apphed more than twice to any one crop. Most fungicide programmes use mixtures of different active ingredients and alternate fungicides with different modes of action to reduce the risk of disease resistance developing. 

Maintenance of conditions ia the culture environment that keep stress to a minimum is one of the best methods of a voiding diseases. Vacciaes have beea developed agaiast several diseases and more are under development. Selective breeding of animals with disease resistance has met with only limited success. Good sanitation and disiafection of contaminated faciUties are important avoidance and control measure. Some disiafectants are Hsted ia Table 6. Poad soils can be sterilized with burnt lime (CaO), hydrated lime [Ca(OH)2], or chlorine compounds (12). 

The Amazon rubber industry collapsed almost overnight. In 1876 the English botanist Henry Wickham shipped 70,000 Hevea seeds to the Royal Botanic Gardens in London. New strains of Hevea were developed that produced three to four times as much mbber and were more disease-resistant than their wild Amazonian cousins. Soon, seedlings were sent to Malaya, Java, and other islands of the East Indies. Thirty-five years later, rubber plantations on these islands took control of the industry. 

As genetic understanding develops, it will be incorporated into basic breeding programs that are concerned with such characteristics as yield, growth habit, insect and disease resistance, flavor, and texture. These programs will be most effective if present ambient ozone and other oxidant concentrations do not increase. 

Qiapter 8 indicates that oxidant air pollutants may adversely affect the olfactory and sight senses, degree of activity, general health and vigor, reproductive rate, heart and kidney function, protein synthesis, respiratory function, and disease resistance in domestic vertebrates under laboratory conditions. Many of these adverse physical responses develop at or near the concentrations of ozone currently experienced daily in ambient air in parts of the San Bernardino Mountains. 

It is clear that we need more novel antibacterials such as linezolid and daptomycin to counter resistance development and appearance of new pathogeiuc bacteria. These will not be easy to come by but continued control of infectious diseases requires them. It is also clear that we need a continuous flow of effective vaccines as a means to protect us from infections in the first place. 

Water polluted by animal faeces poliomyelitis, cholera, typhoid pathogens that cause these diseases are developing resistance to antibiotics. 

In relatively recent years, it has become clear that under-nntrition of mother leads to low birth weight of the baby and this can increase the risk of development of degenerative disease in later life, e.g. hypertension, obesity, type 2 diabetes. One hypothesis is that the foetus adapts meta-bolically to deficiencies by increasing the number of cells in organs that perform specific functions that can overcome the deficiency, e.g. an increase in the number of liver cells that carry out gluconeogenesis, an increase in cells in the adrenal cortex to produce more of the chronic stress hormone, cortisol. These changes are carried over into adnlthood which can lead to an inadequate response of the liver to insulin so that insulin resistance develops. So far, however, it is unclear whether deficiencies in specific nntrients or undemutrition per se are responsible for snch changes (Chapter 15). 

---