It is estimated that there are over 400 people engaged is microbiological scudies dealing with agriculture and industry, mostly in research Work, and some in research administration. They are scattered in some 40 institutions with a heavy concentration on the two universities (National Taiwan University and Chung Hsing University) and Academia Sinica. Nearly 60 percent of the research funds come from sources outside the institution, primarily from the National Science Council (NSC) the Council for Agricultural Planning and Development (CAPD) .
The Council for Agricultural Planning and Development (CAPD) is responsible for program planning as well as research funding; the National Science Council (NSC) is a research funding organization; and the Agricultural Division of the Ministry of Economics is responsible for legal and administrative affairs.
Plant diseases have increased greatly Taiwan, in a tropical climate like ours, natural ecosystem tends to be species rich, and two major trends in the evolution of pathogens can be rationalized. Many of the pathogens may also introduced together with new crops or now cultivars from abroad, particularly the temperate fruittrees. The extensive use of pesticides during the last two decades has also caused significant .changes in the patterns of diseases. Virus/MLO (mycoplasmalike organism) and soil-borne diseases, are now major plant protection problems. Citrus viruses (tristeza, MLO or RLO, and others) have damaged many orchards and are on the brink of ruining the entire industry. The ring spot virus of papaya has shattered our dream of exporting the fruit. No garlic plants are free from mosaic. Tomatoes, peppers, crucifers and cucurbits are multiple-infected with viruses. research projects have been directed at these problems, but answers are still awaiting.
Banana Fusarium wilt or Panama disease is outstanding in soli-borne disease. Rice bakana disease (Fusarium) has long been known. Fusarium of watermelons, pot peas, radishes. sorghum and other crops, has been found increasingly important. Other pathogens, such as Phytophthora and Pythium, render cucumber & melon growing impossible in some areas, and cause great damage to eggplants and other vegetables and to citrus trees. Rhizotania and other fungi and nematodes also cause severe damage.
Of the bacterial disease, the Xanthomonas group are most frequently found, and some Pseudomonas and Erwinia species are also reported. The broad spectrum of P. solanacearum has been found on a number of solanaceous plants.
Many different rice diseases have been found in Taiwan. Blast and sheath blight remain the most serious problems. Traditionally, rice has been grown for two crops per year in Taiwan. In the first crop, neck blast is particularly severe, leaf blast is milder but affects a large area. In the second crop, limited area are affected by blast and only mild infection is found. The disease distribution is island wide. Chemical control of blast is most effective. The effect of fungicides is to inhibit spore germination and penetration. Breeding for disease resistance is the ultimate approach for controlling blast. Most of the varieties presently cultivated are susceptible. The resistance of some rice varieties is not very stable and often breaks down in different parts of the island. Another disease, sheath blight, is considered serious which affects the sheath of the rice plants. High disease incidence is observed in the second crop all over the island, while in the first crop it is found in highest frequency in the central part. For the time being, chemicals offer the only effective control.
Taiwan is one of the chief sugar producing country. Sugar cane diseases are rather diverse, over 56 diseases having been reported. Smut is one of the major diseases while downy mildew is a potentially threatening diseases. The causal agent of the disease is Ustilago scitaminea which infects only sugarcane. The chief control measures are roguing of diseased plants, prohibition of ratooning in diseased plantings arid breeding for disease resistance. Downy mildew is a common disease of sugar cane, having been introduced from Australia.
About 10% of the total agricultural acreage of Taiwan is devoted to fruit Cultivation. Citrus and banana are economically important as they have overseas markets. Citrus diseases found in Taiwan include a number of virus, fungal, bacterial, pleomorphic organism and nematode diseases. Post-harvest disease such as Penicilliumt rot present some problems, it has been reasonably well controlled by applying benomyl and thiabendazol, but resistant strains have been reported recently. Citrus black spot (Guignardia citricarpa) presents more serious problems. Black spot is the most important fungal disease of citrus is Taiwan. The disease is most serious. on sweet orange. In general, chemical control for black spot has been relatively satisfactory, however, its effectiveness may vary with location and variety.
Around 12,000ha. of bananas are cultivated in Taiwan. Sigatoka has been one of the major diseases of banana whereas the freckle disease bas only become important in recent years. The two diseases are somewhat similar in nature, water dispersal in terms of rain is the chief means of pathogen spread. Sigatoka is widely distributed in banana growing countries while freckle is found predominantly is Taiwan and the Philippines. The causal agent of freckle disease is believed to be Phyllosiictina musarum. Sanitation and cehmical control are the chief means for controlling the two diseases. By removing diseasedpleaves, the inoculum can bereduced considerably. Fusarium wilt caused by a new race (race 4) of Fusarium osysporum f. sp. cubense is another disease that seriously threat the banana industry of Taiwan. No effective control has been found so far where disease is severe.
About 300 research projects are carried out annually on plant pathology studies. Their nature is very diverse. It covers taxonomy of rust fungi, sexuality of Phytophthora sp., mycotoxias, healthy seedlings from tissue cultures, ecological studies, chemical control, and plant resistance to diseases etc. Food and feed crops have received more attention because of their large acreages.
For control of plant diseases, various chemical programs have been implemented at DAIS and at other experimental station levels. They include fungicide screening programs which determine the best fungicide and the best concentration to use for control of certain diseases. They also advise farmers on appropriate chemical controls when a question arises.
Various programs of physical control have been implemented, they include internation and domestic quarantines, propagation of disease free materials, disease indexing and certification programs and other control measures through physical means.
Breeding is an expensive, long-term undertaking which requires planning and systematic endeavor. At present, our immediate concern is the actual effectiveness of the resistance, although awareness for horizontal and vertical resistance exists. extensive studies of the subject matter is not feasible at the moment since the genetics of the major crops have not been adequately studied.
|