Biological and molecular characterization of Tomato spotted wilt Virus in Israel

Received April 24, 1997; received in final form June 29, 1997. Symptoms resembling tomato spotted wilt virus (TSWV) infections were documented among ornamental and vegetable crops in commercial greenhouses and open fields in Israel. Plants exhibiting these symptoms were collected from January 1992 to December 1996. Among cultivated plants analyzed for TSWV by enzyme-linked immunosorbent assay (ELISA), 19 species representing five families were found to be infected; natural infection was also recorded in six plant species of weeds. Virus identity was characterized by host range, serology and electron microscopy. Serological reaction with the isolates, found in Israel, using antisera from different sources as well as the sequence analysis of the nucleocapsid gene, demonstrated that the Israeli isolates of TSWV are a member of tospovirus serogroup I, type I (BR-01 strain). No virus transmission was found in seeds collected from virus-infected vegetable and ornamental crops. A non-radioactive molecular probe derived from the cloned nucleocapsid isolate enables specific detection of the virus in crude sap from infected plants. The detection of TSWV in Israel constitutes a severe potential threat to the ornamental and vegetable industry.     

Effects of the host, the pathogen, the environment and their interactions, on fusarium wilt in carnation

Fusarium oxysporum f.sp.dianthi causes severe wilting in carnation (Dianthus caryophyllus L.) worldwide. The pathogen is present in the soil profile in which carnation roots are distributed and may infect the plants at any time during the growing season. To minimize the losses induced by Fusarium wilt, growers use carnation cuttings free ofFusarium spp. and fumigate the soil with methyl bromide prior to planting. The severity of epidemics and the resulting losses are governed by the main and interacting effects of the three components of the disease syndrome: the host, the pathogen and the environment. Host variables include the type and the degree of cultivar resistance (i.e., complete, partial or tolerance); pathogen variables include the race, its virulence and infectivity, and the amount of initial inoculum; environmental variables include solar radiation intensity, photoperiod, temperature and the growth substrate. In the present review the information available on the effect of the host, the pathogen and the environment, and their interactions, on Fusarium wilt in carnation is summarized.     

新一代植酸酶的经济效益

现已证明，在酵母中产生的一种新型的6-植酸酶比其他在市场上供应的植酸酶的效率至少高20％。因为6-植酸酶与其他商品化的植酸酶相比，可进一步减少无机磷源的使用，从而降低生产成本以及磷的污染。     

Monitoring of genetic diversity in the Japanese Black cattle population by the use of pedigree information

The gene pool of the Japanese Black cattle has been completely closed to foreign breeds during the last 100 years. Genetic diversity of the Japanese Black cattle from 1960 to 2000 was monitored with three estimates of effective number of ancestors. Founder genome equivalent (N_ge) accounts for all the causes of reduction of diversity. Effective number of founders (N_ef) and non‐founders (N_enf) explain reduced diversity because of unequal genetic contributions of founders and random genetic drift in non‐founders, respectively. Further examination using gene dropping simulation was conducted to obtain information on survival of founder alleles. Unique founder alleles were dropped down along the actual pedigree with Monte Carlo procedure following Mendelian segregation rules, and generated genotypes of all the current live animals (612 959 heads). Pedigree records consisted of 2 075 188 animals was used for these analysis. The estimates of three effective numbers (N_ef, N_ge, and N_enf) decreased from 418.6 to 50.3, 86.6 to 7.3, and 109.2 to 8.5, respectively, during the period 1960–2000. The increasing differences between two kinds of genetic diversity indices derived from N_ge and N_ef showed that large part of the reduced diversity from 1980 was attributed to genetic drift caused by the intensive use of particular limited number of sires. In gene dropping analysis, probabilities of extinction of founder alleles were derived from their distributions of frequency in the current animals. Several founders showed low probabilities of allele extinction, irrespective of their relatively low genetic contributions. This suggests that these founders have lineages through which their alleles are surely transmitted to the current breed. The use of these founders as a strategy for recovering the genetic diversity was discussed.