This study was carried out to investigate the productivity and the natural disease resistance potential of free-ranging local chickens in Tanzania. A total of 84 adult free-ranging local chicken ecotypes were studied, namely: Mbeya, Morogoro-medium, Ching’wekwe, Kuchi and Singamagazi. Adult body weight, body length, shank length and egg weight were assessed and compared. Average body weight for hens and cocks was 1441g (800 to 2,300g) and 2261g (1000 to 3500g), respectively. Egg weight averaged 41.6g (27 to 72g). Mean body length for hens and cocks was 21.6cm (17 to 26cm) and 24.6cm (21 to 29cm), respectively, and mean shank length 9.7cm (7 to 12cm) and 12.7cm (8.5 to 15cm), respectively. Between ecotypes significant differences were seen in the above parameters. The disease resistance potential was tested on 10 offspring of each ecotype, excluding the Mbeya. Twenty chickens (five from each of the four ecotypes) aged 12 weeks were inoculated with Newcastle disease virus while another 20 aged 20 weeks were inoculated with Salmonella gallinarum. Five chickens per group that were not challenged were used as controls. Following oral, ocular and nasal drop inoculation with Newcastle disease virus, the chickens developed clinical signs of Newcastle disease as from day three after infection. Mortality started on day five after infection, and all but one chicken were dead by day seven after infection. The 20 chickens, infected orally with S. gallinarum, showed clinical signs of fowl typhoid on day three after infection. Mortalities started on day seven after infection and by day 12 after infection 13 chickens had died. Seven birds survived without visible signs of the disease, including all five from the Kuchi ecotype and one each of the Morogoro-medium and Ching’wekwe ecotypes. At necropsy enlarged and congested liver and spleen, and catarrhal enteritis of the small intestines were seen. The surviving birds were sacrificed on day 14 after infection. Neither the sacrificed surviving birds nor the controls showed the above necropsy picture. It was concluded that free-ranging local chicken ecotypes in Tanzania differ in both productivity and disease resistance potential.

The study was designed to evaluate the immune response of chickens among different poultry management following challenge to live La Sota vaccine and further more investigated the lower antibody response detected in traditionally managed chicken, by testing the hypothesis that veterinary intervention (treatment with anti-helminthic, antibiotics and vitamin supplements), prior to vaccination, would improve the antibody response to live NDV vaccination. Even if, a protective level of antibody (> 4 Log 2HAI) was detected in all chickens following vaccination, antibody titres were significantly higher (p < 0.05) in the intensively managed chickens Geometric Mean Titre (GMT) 85.4 when compared with the traditionally managed chickens GMT 59.3. From multivariable analysis; following a single live ND virus vaccine at the age of 21 day, chickens rearing in intensive production system were 8.6 times more likely to have high titre (128 vs 32) compared to those rearing in backyard free ranging system. The lower ND-HI titre in extensively managed chickens recorded in our study had be explained by impaired immune-competence due to immune-suppressive of concurrent infection. The study investigated the effect of concurrent parasitic and viral diseases on the immune response; as well as differences in protection among indigenous ecotype and exotic breed of chicken. The hypothesis that parasitism contributes to a poorer response to vaccination was proven (p < 0.05). Chickens that received veterinary treatment (de-wormed chickens) prior to vaccination were approximately 14 (i.e. 14.3) times more likely to have a titre of 128 when compared to titre 32 showing evidence for veterinary intervention had detectable effect on humoral response of chicken to vaccination (p< 0.05). Moreover; it was evident that HI titer differed between individual chickens and was influenced by breed types. Multivariate analysis showed that indigenous chickens were about 7 times more likely to have high HI titre (128 vs 32) compared to exotic breeds (p< 0.05). Though breeds differ genetically in their immune responsiveness to the antigen, and being protected following challenge; difference in their susceptibility to the virulent challenge virus needs to be ruled out in order to facilitate the improvement of disease-resistant traits.

Weather conditions in Latvia are very favourable for the development of potato late blight caused by Phytophthora infestans (Mont) de Bary. The control of potato late blight can be performed using different approaches: standardised technology, prognoses of the first infection and prognoses of the progress of disease development. The negative prognosis model Negfry is based on the last two mentioned above. For the control of potato late blight in Latvia mainly has been used - standardised technology. The first field treatment was made during the row closing or according to prognoses. Regular treatments were made each 8-14 days. The use of NegFry model started in Latvia in 1998. Local varieties and weather data have been used for the trial. For the control of potato late blight in field trials standartised fungicide application was compared with the NegFry model and the untreated variant. The major task of the use of the model is possibility to reduce the number of fungicide treatments. The NegFry model helps to realise an integrated plant protection system, which decreases fungicide application and increases economical efficiency.

Potato is the second important crop in Latvia. The area covered with potato is about 50 thousand hectares. Potato late blight caused by Phytophthora infestans (Mont.) de Bary is the most serious potato disease. Weather conditions in Latvia are very favourable for the development of potato late blight and it is occuring almost every year. The biology of P.infestans was the subject of a number of authors - plant pathologists. Research results about P.infestans population biology and epidemiology are presented in this review, especially focusing on the changes of pathogen biology.

Late blight (Phytophthora infestans) is one of the most serious potato diseases. The light blight forecasting is a very important factor for the protection of potato plants. NEGFRY is a decision support system for scheduling the chemical control of potato late blight. Trials were carried out in 2000-2001 at the Lithuanian Institute of Agriculture (LIA) in Dotnuva in medium early and moderately susceptible to late blight varieties. Ordinary plant protection systems against late blight and different NEGFRY models were compared. Results of two years' investigations show that by using NEGFRY models we can obtain satisfactory protection of potato crop and get higher yield using fewer spray applications.

One of the most serious diseases of the potato crop worldwide is late blight caused by Phytophthora infestans (Mont.) de Bary. Most growers control the disease by applying fungicides at regular intervals of 8-10 days from the time of row closing until the end of the growing season. The NEGFRY model is used for timing the chemical control of potato late blight. The NEGFRY model is based on two existing models, the "negative prognosis", for forecasting the risk of primary attacks, and a model for timing subsequent fungicide applications during the season. The main objective of NEGFRY is to get high yield and quality with minimum use of fungicides. Present work underlies the experiments that were arranged in 2000 and 2001 at the Jogeva Plant Breeding Institute. Two potato varieties with different resistance to late blight were taken to the experiment in both years: susceptible 'Adora' and modarately resistant 'Anti' in the year 2000 and susceptible 'Berber' and 'Anti' in 2001. NEGFRY gave highest economical effect among six tested treatment regimes.