detected correspond to VCGs which have been already characterized for pathogenic isolates in the past. No new VCGs specific to soil have been revealed. Rather unexpectedly most isolates were assigned to VCG 1, not frequently present in Europe. So far VCG 1 was restricted to several Verticillium dahliae isolates pathogenic to cotton, grown in several countries, including Spain (Puhalla 1979, Zbengjan et al. 1996, Karolev et al.2000).
Races of Puccinia triticina identified in various regions of Russia in 2000-2002
Zhemchuzhina A.I., Kurkova N.N., Kovalenko E. D.
All Russian Research Institute of Phytopathology, 143050, B. Vyazemy, Moscow region, Russia
Urediospore isolates of Puccinia triticina have been received from leaf samples of wheat from 7 regions of Russia (Northwest, Central, Volgo Vyatka, North Caucasian, Middle Volga, Low Volga, Western-Siberian) in 2000 and from 8 regions (Central, Volgo Vyatka, North Caucasian, Central Chernozem, Middle Volga, Low Volga, Western-Siberian, East-Siberian) in 2001 and 2002. 55 leaf rust races were identified on the set of 12 near isogenic lines of cv. Thatcher (LR 1, 2a, 2c, 3a, 3ka, 9, 11, 16, 17, 24, 26, 30): there were 36 races identified from 368 single isolates in 2000, 32 races from 394 isolates in 2001 and 46 races from 507 isolates in 2002. As all investigated isolates were virulent to Lr 3a, the identified races have been related to 8 groups of races: C- (virulence to Lr 3а), F- (virulence to Lr 2c, 3а), H- (virulence to Lr 2a, 3а), K- (virulence to Lr 2a, 2c, 3а), M- (virulence to Lr 1, 3а), P- (virulence to Lr 1, 2c, 3а), R- (virulence to Lr 1, 2а, 3а), Т- (virulence to Lr 1, 2a, 2c, 3а). Distinctions between regional populations of P. triticina on frequency of occurrence of racial groups and separate races of pathogen are established. The races belonging to C-group in 2000 were widespread on wheat in the European territory of Russia and extremely rare in the Western and East Siberia. The races CGК (virulence to Lr 3a, 11,16, 17,30) and CGT (virulence to Lr 3a, 3ka, 11, 16, 17, 30) are dated to Volgo Vyatka and to North Caucasian region, CBK (virulence to Lr 3a, 11, 17, 30) and CBT (virulence to Lr 3a, 3ka, 11, 17, 30) - to Middle Volga and Low Volga regions. Races CGК and CBК dominated in the Northwest region. Races of M-group annually dominated over the European leaf rust population and very seldom appeared in Siberia. From the M-group, the race МВТ (virulence to Lr 1, 3a, 3ka, 11, 17, 30) dominated in Central Chernozem, Volgo Vyatka and North Caucasian region In other regions it had insignificant concentrations. Races belonging to the T-group were identified in all regions annually, but in the Asian territory of Russia (Western and Eastern Siberia) they were found 1,5-2 times often. From races of this group, the race TVT (virulence to Lr 1, 2а, 2с, 3a, 3ka, 11, 17, 30) dominated in marks regions, except for Northern Caucasus where it was rare. In particular, it was found frequently on Middle and the Low Volga, in Western and Eastern Siberia. The race ТСТ (virulence to Lr 1, 2а, 2с, 3a, 3ka, 11, 17, 26, 30) was identified frequently in the last 2 regions and also in Northwest. Occurrence of Р-race was insignificant in the Central Chernozem and Eastern Siberia regions. Race РВТ (virulence to Lr 1, 2с, 3a, 3ka, 11, 17, 30) in 2002 dominated in Volgo Vyatka and the Western-Siberian populations. Races of R-group were absent in leaf rust populations on Northern Caucasus. In other regions they had insignificant amount of isolates. Races of F-group, on the contrary, annually were determined in populations of Northern Caucasus but in other regions they were not found out frequently. Race FHT (virulence to Lr 2с, 3a, 3ka, 11, 16, 17, 26, 30) dominated over a North Caucasian population in 2002. Races of H-group have not been found out in Volgo Vyatka, North Caucasian, Middle Volga and the Western-Siberian populations. Races of K-group were absent in Central and Volgo Vyatka populations P. triticina. Comparison of Rodger’s indexes of racial structure similarity of the investigated populations have shown that the most precise distinctions were revealed between North Caucasian and all other regions.
Variability of Collectotrichum gloeosporioides isolates from yam in South Pacific islands.
JAMA A.N1, PETERS J.C.2, GOWEN S.R1, CANNON. P3 and ENSENT. J3
1Department of Agriculture, Earley Gate, The University of Reading, Reading, UK, 2 British Potato Council, East bank, Sutton Bridge, Spalding UK, 3CABI-Biosciences, Bake lane, Egham, Surrey, UK.
Yam anthracnose is one of the main causes of economic loss in yam crops worldwide. The causal organism, Colletotrichum gloeosporioides is known to have a wide host range (Murdue, 1977, Descriptions of Plant Pathogenic Fungi and Bacteria, No. 315. Kew, UK. Commonwealth Mycological Institute; Jefferies et al., 1990, Plant Pathology 39, 343-366). However, in the South Pacific, along with other yam growing countries, the epidemiology of the disease has not been fully elucidated. In this study, we focused on the variability of 61 South Pacific isolates of C. gloeosporioides obtained from yam and six non-yam hosts. These isolates revealed high heterogeneity and complex patterns in both morphology and molecular fingerprinting. At the morphological level, isolates clustered into three main phenotypes, consistently distinguishable by their colony and conidial characteristics and their ability to produce the sexual stage, Glomerella cingulata. Moreover, there were strong similarities between these morphological phenotypes and the cluster patterns generated by DNA fingerprints obtained by inter-simple sequence repeat (ISSR) PCR amplification. However, only limited associations were detected between morphology and those molecular groupings obtained from amplified fragment length polymorphism (AFLP) PCR analysis as well as between the two molecular patterns produced by ISRR-PCR and AFLP-PCR techniques. Moreover, although variations in pathogenicity among 49 of the 61 isolates on the yam, Dioscorea alata cv. White Lisbon, showed significant differences (P< 0.001), there was no clear relationship linking isolate pathogenicity either to their morphological or molecular variations. Moreover, despite the existence of notable genetic diversity among some isolates within a given locality, close genetic relatedness was observed among the isolates collected from different South Pacific countries. This indicates that C. gloeosporioides populations in these countries are not entirely distinct. Furthermore, in this study, we report the existence of C. gloeosporioides isolates able to cause cross-infections between yam and non–yam hosts. We also report the occurrence of C. gloeosporioides infections in yam tubers under field conditions. This highlights the importance of infected seed tubers as potential sources of infection.