Characterization of two races of the stem and bulb nematode (Ditylenchus dipsaci) in Israel

Two distinct races ofDitylenchus dipsaci in Israel were identified: one, which infects and damages onion and garlic, reproduces on pea, but does not infect phalaris grass; and a second, which infects and damages phalaris—and, probably, also ‘Saia’ oats—but fails to infect onion and garlic. A new ‘garlic’ race of the nematode does not appear to have been introduced into Israel together with the ‘Lavinia’ garlic cultivar, as previously speculated, but rather the introduced Lavinia clone is highly susceptible to the existing ‘onion and garlic’ race ofD. dipsaci.     

Pathogenic races and inoculum density ofFusarium oxysporum f.sp.niveum in commercial watermelon fields in southern Turkey

Systematic surveys forFusarium oxysporum f.sp.niveum (Fon) were conducted in a total of 141 fields in the watermelon-growing areas of the Mediterranean and southeastern Anatolia regions of Turkey in 2004 and 2005. The mean incidence and prevalence of the disease were higher in the southeastern Anatolia region than in the Mediterranean region. Maximum disease incidence during the 2-year survey was 46.3%. However, mean disease prevalence ranged from 27.3% to 63.6% in southern Turkey. Of the 33 isolates ofFon recovered, 19 were recovered from Adana, two from Mersin, one from Gaziantep, four from Sanlıurfa, five from Adıyaman, one from Batman, one from Diyarbakır. The physiological race of each isolate was determined by the disease reaction in five differential watermelon cultivars (Citrullus lanatus (Thunb.) Matsum. & Nakai). Of the isolates recovered from the Mediterranean region, 47.6% were identified as race 0, 38.1% as race 1, and 14.3% as race 2. Among the 12 isolates recovered from the southeastern Anatolia region, four isolates were identified as race 0, and eight isolates as race 1. Race 2 was not detected in this region. This is the first report ofFon races 0 and 1 in southeastern Anatolia. The population density ofFon in both the Mediterranean and southeastern Anatolia regions ranged from 116.1 to 4444.7 CFU g⁻¹ of soil. The mean inoculum density was much higher in watermelon-growing areas in the southeastern Anatolia region in comparison with the Mediterranean region, with a mean inoculum density of 1547.2 CFU g⁻¹. Race 0 and race 1 were the most prevalent races in the fields with the mean highest and lowest inoculum density, respectively. http://www.phytoparasitica.org posting March 10, 2008.     

Occurrence of races and pathotypes of cucurbit powdery mildew in southeastern Spain

The causal agent of cucurbit powdery mildew in southeastern Spain has been investigated since 1996. Of the 139 single-spore isolates obtained, all were identified asSphaerotheca fusca. Four physiological races (1, 2, 4 and 5) of the pathogen were detected. During the survey, a population shift ofS. fusca was observed: race 1 was progressively replaced by other races. In addition, race coexistence was observed in several cucurbit greenhouses. Four host range patterns or pathotypes were distinguished among the isolates ofS. fusca. All isolates were highly aggressive on melon and especially on zucchini cultivars. No clear relationships between races and pathotypes could be established, although isolates virulent on watermelon were preferentially associated with race 1. These data show an apparent heterogeneity ofS. fusca populations in southeastern Spain that should be analyzed further. http://www.phytoparasitica.org posting Aug. 9, 2002.     

Occurrence of Fusarium oxysporum f. sp. melonis Race 1 in Japan

In 1994, Fusarium wilt of melon cultivars which are resistant to races 0 and 2 of Fusarium oxysporum f. sp. melonis was observed in southern area of the Lake Biwa region, Shiga prefecture. In commercial fields, mature plants of cv. Amus which were grafted onto cv. Enken Daigi 2, and of cv. FR Amus showed yellowing, wilting and finally death before harvesting of fruits. Diseased plants had vascular and root discolorations, and their stem sections yielded typical colonies of F. oxysporum. When the Shiga strains were tested for their pathogenicity to 12 species of cucurbits, they caused wilts only on melon. Using race differential cultivars of melon, the Shiga strains were classified as race 1 of F. oxysporum f. sp. melonis, which has not been reported in Japan. To further characterize their pathogenicity, the strains were used to inoculate 46 additional cultivars of melon, oriental melon and oriental pickling melon. All the race 1 strains were pathogenic to the cultivars tested, and their host range was apparently different from those of strains belonging to other races (races 0, 2 and 1,2y). DNA fingerprinting with a repetitive DNA sequence, FOLR3, differentiated race 1 strains from strains of races 0 and 2, but not from race 1,2y strains. Received 2 July 1999/ Accepted in revised form 30 September 1999     

Monitoring physiological races of<Emphasis Type="Italic">Podosphaera xanthii</Emphasis> (syn.<Emphasis Type="Italic">Sphaerotheca fuliginea</Emphasis>), the causal agent of powdery mildew in cucurbits: Factors affecting race identification and the importance for research and commerce

Identification of the physiological races ofPodosphaera xanthii (syn.Sphaerotheca fuliginea), the causal agent of powdery mildew in cucurbits, is based upon the differing responses of various melon cultigens to the pathogen. Eight races of the pathogen have been identified to date in the USA, Africa, Europe and around the Mediterranean Sea, and four new races were reported from greenhouse melons in the major growing area of Japan. Plant responses to powdery mildew may be affected by environmental factors such as light intensity, temperature and humidity, as well as by age and nutritional status of the plants. The same factors affect the accuracy and reliability of race identification. In an attempt to overcome those obstacles, the genetic diversity ofP. xanthii was studied using molecular markers. Unfortunately, no correlation was found between DNA polymorphism and the race of the pathogen as identified by biological tests. The usefulness of race identification as a guide for the grower in selecting appropriate cultivars is limited because changes or shifts in the pathogen population are common. Such changes may be found among growing seasons, geographic regions and hosts, and also within a single greenhouse during a single season. On the other hand, race identification is important for basic research and is especially important for the commercial seed industry, which requires accuracy in declaring the type and level of resistance to powdery mildew in its products. http://www.phytoparasitica.org posting March 2, 2004. Contribution from the Agricultural Research Organization. No. 501/04.     

Development of sequence tagged site markers to identify races of Fusarium oxysporum f. sp. lactucae

By random amplified polymorphic DNA (RAPD) analysis of the representative isolates of each race of Fusarium oxysporum f. sp. lactucae, RAPD fragments of 0.6, 1.6, and 2.9kb were obtained. The 0.6-kb RAPD fragment was common to the representative isolates of all three races. Amplification of the 1.6- and 2.9-kb fragments were unique to the isolates of races 1 and 2, respectively. Sequence tagged site (STS) marker FLA0001, FLA0101, and FLA0201 were generated from the 0.6-, 1.6-, and 2.9-kb RAPD fragments, respectively. Polymerase chain reaction (PCR) analysis showed that FLA0001 was common to all 49 isolates of F. oxysporum f. sp. lactucae. FLA0101 was specifically generated from all 23 isolates of race 1 but not from races 2 or 3. FLA0201 was specifically amplified from all 12 isolates of race 2 but not from races 1 or 3. In two isolates of F. oxysporum f. sp. lactucum, PCR amplified FLA0001 and FLA0101 but not FLA0201. On the other hand, these STS markers were not detected from isolates of five other formae speciales. Because these STS markers were not generated from isolates of other plant pathogenic fungi, bacteria, or plant materials examined in this study, PCR analysis combined with the three STS markers should be a useful means for rapid identification of races of F. oxysporum f. sp. lactucae.     

Host genotype- and temperature-dependent colonizationof In vitro carnation callus cultures byFusarium oxysporum f.sp.dianthi race 2

Differentin vivo resistance/susceptibility levels of 14 carnation cultivars toFusarium oxysporum f.sp.dianthi race 2, the causal agent of Fusarium wilt disease of carnation, were also expressed in anin vitro system and assayed as the degree of fungal colonization of callus cultures at 20° C. Temperature influenced thein vitro expression of carnation resistance. An incubation temperature of 27° C increased the colonization of calli derived from both the susceptible (‘Corrida’ and ‘Ambra’) and the resistant (‘Pulcino’ and ‘Pallas’) cultivars. At 15°C, the colonization of calli derived from Pulcino and Pallas diminished significantly more than for Ambra and Corrida. Inhibition of fungal growth on resistant calli was correlated to retardation in hyphal development. Both scanning electron microscopy and light microscopy observations showed that hyphae did not penetrate into carnation cells.     

Toxic culture filtrates produced byCalonectria ilicicola, causal agent of red crown rot of soybean

Eleven soybean cultivars with different levels of susceptibility to virulent isolate SG915 ofCalonectria ilicicola were examined for reaction to metabolites produced by the isolate. When the culture filtrate from isolate SG915 was applied to trifoliates from 11 cultivars, cvs. ‘Cajun’ and ‘Asgrow 7986’ exhibited reduced wilting severity. However, there was no correlation between sensitivity to culture filtrate and susceptibility to the fungal isolate. Wilting severity on cv. ‘Riverside 699’ was greatest when trifoliates were treated with culture filtrates from isolates SG915 (highly virulent) and C31 (less virulent). The dilution end-point for culture filtrates of virulent isolate SG915 was determined to be 1:8. Nonautoclaved culture filtrates caused complete wilt of soybean trifoliates after 36 h, but autoclaved culture filtrates demonstrated a reduced ability to wilt leaves. Electrolyte leakage from treated leaf tissues increased over time regardless of the concentrations of culture filtrate tested. The greatest electrolyte losses were observed during the initial 30 min incubation of leaf tissues. The highest concentration of culture filtrate (50%, v/v) induced more electrolyte loss than the low concentration (10%, v/v) or control. These results suggest that toxic metabolites ofC. ilicicola may be involved in disease development with leaf symptom expression.     

Extracts of killedPenicillium chrysogenum Induce resistance against Fusarium wilt of melon

Dry fungal biomass ofPenicillium chrysogenum (dry mycelium), a waste product of the pharmaceutical industry, was extracted with water and applied to the roots of melon plants before or after inoculation withFusarium oxysporum f.sp.melonis (Font). Seedlings (4–6 days after emergence) treated with either acidic dry mycelium extract (DME) or neutralized dry mycelium extract (NDME) were protected against challenge infection withFom. A single drench with 2–5% DME applied 12–72 h before inoculation provided significant control of the disease compared with water-drenched, challenged seedlings. No protection was seen in plants treated 0–6 h before inoculation or 0–48 h after inoculation. Neither DME nor NDME (0.5–5%) had any effect on fungal growthin vitro, which implied that disease controlin vivo was mediated by induced resistance. The resistance induced by DME protected melon plants not only against race 1,2, but also against the three other races of the pathogen, indicating a race-non-specific resistance againstFom. Both DME and NDME significantly increased peroxidase activity and free L-proline content in seedlings 12 h and 48 h after soil drench, respectively. Resistance to Fusarium wilt was significantly associated with elevated levels of peroxidase activity but not with free L-proline content. Thus, peroxidase might be involved in the defense mechanisms activated by DME or NDME. http://www.phytoparasitica.org posting Aug. 31, 2001.     

Development and fecundity ofSitobion avenae on some wheat cultivars under laboratory conditions

Nymphal development time and fecundity ofSitobion avenae (F.) (Homoptera: Aphididae) were determined on nine widespread wheat varieties cultivated in Tekirdağ Region in Turkey. Tests were carried out in controlled environment chambers (25±1°C, 65±5% r.h.; 16:8, L:D). Development time (±S.E.) ranged from 5.75±0.25 to 7.20±0.20 days. Fecundity per female ofS. avenae was found to be the highest (12.87±1.50) on wheat cv. ‘Sana’. In this investigation cvs. ‘MV-17’, ‘Miryana’, ‘Pehlivan’ and ‘Saraybosna’ were particularly resistant againstS. avenae. http://www.phytoparasitica.org posting July 8, 2002.     

Population structure,races, and host range of <Emphasis Type="Italic">Aphanomyces euteiches</Emphasis> from alfalfa production fields in the central USA

Aphanomyces euteiches (races 1 and 2) causes root rot of alfalfa; however, its population biology and distribution are poorly understood where alfalfa is a major crop. The objectives of this study were to (1) characterise the distribution and frequency of races of A. euteiches in Illinois alfalfa fields, (2) determine host range of A. euteiches on cultivated and native legumes, and (iii) to describe genetic diversity and population genetic structure of A. euteiches in alfalfa fields. To accomplish this, soil samples (n = 103) were collected from 30 alfalfa fields in 18 Illinois counties. Using the susceptible cv. ‘Saranac’, 148 isolates of A. euteiches were baited from the soil. The virulence phenotype of isolates representing all 18 counties was tested, and 54% were R1 and 46% were R2. Both races were detected in 61% of the counties, whereas only R1 was detected in 22% and R2 in 17%. Thirteen legume hosts for isolates from alfalfa fields were identified based on symptoms and/or production of oospores in roots. In addition to six previously known hosts, seven species were susceptible to infection: kura clover, purple prairie clover, white prairie clover, ladino clover, hairy vetch, Canadian milk vetch, and Illinois tick trefoil. AFLP analysis revealed high levels of genetic diversity among the isolates from different fields and counties and a lack of genetic structuring of populations based on race or geographical origin. The results suggest that populations of A. euteiches in alfalfa fields are diverse, often composed of races 1 and 2, and create risk for alfalfa and to multiple cultivated and native legume species.     

Pathogenic races of the melon-wilt Fusarium in Israel

Two races ofFusarium oxysporum f. sp.melonis were identified among 54 isolates of this pathogen, tested on three differential lines of melon. Of the two races, race 0 was the more prevalent, comprising 92.5% of the total number of isolates tested. Race 1 has been encountered so far in one growing area only. The identity of the local races is compared with those defined in France and in two areas of melon-growing in California.     

Rootstock resistance to Fusarium wilt and effect on watermelon fruit yield and quality

The potential of grafted watermelon for resistance toFusarium oxysporum f.sp.niveum on some Curcurbitaceae,Lagenaria, Luffa, Benincasa and commercial rootstocks was evaluated. Effects of grafting on yield and quality of diseased plants were evaluated. All grafted plants and rootstocks were resistant to the three known races (0, 1, and 2) ofF. oxysporum f.sp.niveum except watermelon cv. ‘Crimson Tide’, which was susceptible to race 2. Fruit yield was positively (21–112%) affected byLagenaria rootstocks but negatively affected (200–267%) byCucurbita rootstocks when compared with the control. While only minor differences in fruit quality were determined in control and grafted plants onLagenaria rootstocks, the quality parameters for watermelon grafted ontoCucurbita rootstocks were lower than in the control. The reasons for low yield and quality might be due to an incompatibility betweenCucurbita rootstocks and watermelon. These results showed that rootstock influence on disease resistance as well as yield and quality of scion fruit is important in determining the potential use of grafting applications in watermelon. http://www.phytoparasitica.org posting Feb. 2, 2003.     

Lack of influence of host plant disease resistance on the evolution of resistance to sterol demethylation-inhibiting (DMI) fungicides in<Emphasis Type="Italic">Cercospora beticola</Emphasis>

Field experiments were conducted during 1997 and 1998 to determine the effects of sugar beet cultivar susceptibility to Cercospora leaf-spot on the sensitivity ofCercospora beticola isolates to the triazole fungicide flutriafol. Four cultivars with different levels of disease resistance were treated in experimental plots with six spray applications of flutriafol. Disease assessments were carried out at 15-day intervals. Sensitivity to flutriafol was measured on isolates collected from the plots ∼15 days after the last flutriafol application. Measurements of disease severity and calculations of AUDPC (area under disease progress curve) values showed a distinct differentiation among cultivars, reflecting their level of disease resistance. Disease severity was significantly lower in cvs. ‘Bianca’ and ‘Areth’ than in ‘Univers’ and ‘Rizor’ both in the untreated and in the flutriafol-treated plots. Fungal isolates from flutriafol-treated plots were less sensitive to the fungicide than were isolates from untreated plots. However, no differences in isolate sensitivity were observed among the cultivars, as regards their level of disease resistance. Despite the fact that the use of resistant cultivars cannot eliminate selectively the resistant strains, it can eliminate both resistant and sensitive isolates. Reducing the number of treatments with DMIs, by applying them only when environmental conditions are favorable for disease development, is a prerequisite for successful resistance management; therefore, the use of disease-resistant varieties could aid toward management of DMIs resistance inC. beticola. http://www.phytoparasitica.org posting May 6, 2003.     

Differences in pathogenesis observed among susceptible interactions of carnation with four races of Fusarium oxysporum f.sp. dianthi

Susceptible interactions of Early Sam carnations with races 1,2,4, and 8 ofFusarium oxysporum f. sp.dianthi differed in pathogenesis, both after stem and after root inoculation. Race 1 induced pallescence and withering of leaves. Affected vascular tissue had a uniform pallid to pale brown colour; though heavily colonized, it was not or virtually not degraded. Defence reactions developed only slowly. Race 2 induced yellowing, of the midribs in particular, and withering of leaves. Affected vascular tissue was white with dark brown margins. Colonized tissue was degraded to leave vascular cavities. At lower heights of colonization, many defence reactions developed, which sometimes resulted in localization of the pathogen. Race 4 induced a similar pathogenesis as race 2, except for less intensive defence reactions. Race 8 induced midrib lesions on, and pallescence, withering and necrosis of leaves. Affected vascular tissue had a uniform light brown colour. Degradation of colonized vascular tissues was rare; instead, many defence reactions were observed, even at high heights in the plants.Races 1, 2 and 4 ofF. oxysporum f. sp.dianthi did not induce disease symptoms in Novada carnations, known to be highly resistant to race 2. Stem-inoculated plants localized the infection close to the inoculation site; stems of root-inoculated plants remained unaffected. The localization response also occurred in Early Sam and Novada carnations stem-inoculated withF. oxysporum f. sp.lycopersici.Samenvatting Tussen interacties van Early Sam-anjers met fysio's 1, 2, 4 en 8 vanF. oxysporum f. sp.dianthi werden verschillen in ziekteontwikkeling gevonden na wortel-zowel als stengelinoculatie. Fysio 1 gaf verbleking en verdroging van de bladeren. Aangetast vaatweefsel was gelijkmatig vaal of lichtbruin van kleur, en werd hevig gekoloniseerd, maar vrijwel niet afgebroken. Afweerreacties kwamen slechts traag op gang. Fysio 2 gaf vergeling, in het bijzonder van de hoofdnerven, en verdroging van de bladeren. Aangetast vaatweefsel was wit met donkerbruine randen. Gekoloniseerd weefsel werd afgebroken, hetgeen leidde tot de vorming van holten in het vaatweefsel. In de lagere gekoloniseerde delen traden veel afweerreacties op, hetgeen soms lokalisatie van het pathogeen tot gevolg had. Fysio 4 gaf eenzelfde ziekteontwikkeling als fysio 2, maar minder afweerreacties. Fysio 8 gaf lesies bij de hoofdnerven, en verbleking, verdroging en necrose van bladeren. Aangetast vaatweefsel was gelijkmatig lichtbruin van kleur. Afbraak van gekoloniseerd vaatweefsel werd zelden waargenomen; veel afweerreacties vergezelden de kolonisatie tot hoog in de stengel.Inoculatie van Novada anjers met fysio's 1,2 en 4 vanF. oxysporum f. sp.dianthi had geen ziektesymptomen tot gevolg. Via de stengel geïnoculeerde planten lokaliseerden de infectie ter hoogte van het inoculatiepunt; de stengels van via de wortels geïnoculeerde planten waren onaangetast. De lokalisatiereactie trad ook op in Early Sam en Novada anjers na inoculatie via de stengel metf. oxysporum f. sp.lycopersici.     

Induced resistance in cotton seedlings against fusarium wilt by dried biomass of<Emphasis Type="Italic">Penicillium chrysogenum</Emphasis> and its water extract

Dry mycelium (DM) of killedPenicillium chrysogenum and its water extract (DME) were used to induce resistance in cotton plants againstFusarium oxysporum f.sp.vasinfectum (Fov). Results showed that the efficacy of either DM or DME in controlling the disease depends on both the concentration and the mode of application. DM amended to the soil at 0.25–2% (w/w) provided 32–75% protection againstFov. Soil drench with 2–5% DME (w/v) and pre-sowing seed soakage with 5–10% DME provided 51–77% and 28–35% protection against the wilt disease, respectively, whereas no protection was obtained with foliar sprays of 1–10% DME. DM and its water extract had no direct antifungal activity on growth ofFov in vitro, suggesting that disease control with DM or DME resulted from the induction of natural defense mechanisms in the cotton plants. Soil drench with 5% DME was as effective as 2% DM powder in inducing resistance againstFov, implying that the resistance-inducing substances were mostly water-soluble. Four cotton cultivars with various genetic resistance levels againstFov were tested at the seedling stage: two resistant ‘Pima’ cultivars and two susceptible ‘Acala’ cultivars. The level of protection achieved in the two susceptible cultivars with DME was equal to, or higher than, that of the two resistant cultivars treated with water. Innate and induced peroxidase activity in cotyledons or hypocotyls and roots coincided with the level of genetic resistance and DME-induced resistance, respectively. Based on our results, an integrated control strategy ofFov with both genetic resistance and induced resistance is suggested.     

Physiological races and vegetative compatibility groups of butterhead lettuce isolates of Fusarium oxysporum f. sp. lactucae in Japan

Races were identified among butterhead lettuce isolates of Fusarium oxysporum f. sp. lactucae collected from three geographical areas of Hokkaido, Shizuoka, and Fukuoka in Japan by inoculation tests using Fujinagas race differential cultivars of lettuce (i.e., Patriot, Costa Rica No. 4, and Banchu Red Fire). Eighteen isolates from Shizuoka and Fukuoka were designated race 3, with two unknown vegetative compatibility groups (VCGs) that differed from Ogisos VCG 1 and 2. These two new VCGs were obtained from both Shizuoka and Fukuoka. On the other hand, three isolates from Hokkaido were classified as race 1 and identified as VCG 1, which represents a VCG of crisphead isolates from Nagano.     

Physiological races and vegetative compatibility groups within Fusarium oxysporum f.sp. gladioli

The pathogenicity and vegetative compatibility of mainly Dutch isolates ofFusarium oxysporum collected from diseased gladioli and other Iridaceae were investigated. Based on their pathogenicity to two differential gladiolus cultivars, the isolates could tentatively be divided into two races. All self-compatible isolates ofFusarium oxysporum f.sp.gladioli belonged to one of three distinct vegetative compatibility groups, VCG 0340, 0341 or 0342, and were incompatible with isolates that were not pathogenic to gladiolus. Isolates of one of the two races were restricted to one VCG while isolates of the other race were present in all three VCGs.     

Production of Beauvericin by Different Races of Fusarium Oxysporum F. sp. Melonis, The Fusarium Wilt Agent of Muskmelon

Fourty-four strains of Fusarium oxysporum were isolated from plants of melon with Fusarium wilt symptoms. Among these strains, thirty-nine were characterized for their pathogenicity on melon. Thirty-seven strains belonged to known races of F. oxysporum f. sp. melonis, while two strains were non-pathogenic. Four strains belonged to race 0, seven to race 1, four to race 2, and twenty-two to race 1,2. Beauvericin was produced by thirty-six strains in a range from 1 to 310gg^–1. Eight isolates of race 1,2 did not produce the toxin. In addition, of the two non-pathogenic strains, only one strain produced the toxin (290gg^–1). The production of enniatin A₁, enniatin B₁, and enniatin B was also investigated. Enniatin B was the only enniatin detected, being produced by eleven strains belonging to all the races, with a range of production from traces to 60gg^–1. Finally, melon fruits belonging to two different cultivars (Cantalupo and Amarillo) were artificially inoculated with one strain of F. oxysporum f. sp. melonis (ITEM 3464). Beauvericin was detected in the fruit tissues of both cultivars at a level of 11.2 and 73.8gg^–1, respectively. These data suggest that the production of both the toxins is not related to the pathogenicity of F. oxysporum f. sp. melonis, nor to the differential specificity of the races. The results confirm that beauvericin is a common metabolite of phytopathogenic Fusarium species.     

Race distribution of Phytophthora sojae on soybean in Hyogo, Japan

Since 1987, Phytophthora root and stem rot of soybean [Glycine max (L.) Merr. cv. Tanbakuro], caused by Phytophthora sojae Kaufman and Gerdemann, has been increasing in the Sasayama, Nishiwaki, and Kasai regions in Hyogo, the most famous soybean (cv. Tanbakuro)-producing areas in Japan. In 2002 to 2004, 51 isolates (one from each field) of P. sojae were recovered from 51 fields in Hyogo. These isolates were tested for virulence on six Japanese differential soybean cultivars used for race determination in Japan, and three additional ones containing four Rps genes used in Indiana, USA. Race E was the most prevalent from 2002 to 2004, followed by races A, C, D, and four new races (proposed as races K, L, M, and N). Interestingly, none of the new races had high virulence on the Japanese differential cultivars, compared with other races in each area. One (race N) was avirulent on all six soybean differentials. There was a difference in race distribution on each of three individual areas; race E seemed to be a major component of the P. sojae population in Sasayama, whereas race A and the new race M were the most prevalent in Nishiwaki and Kasai, respectively. Rps6 (cv. Altona) and Rps1a + Rps7 (cv. Harosoy 63) were infected by 90.2% and 33.3% of all isolates, respectively. However, Rps1d (cv. PI103091) was not susceptible to any of the 51 isolates, nor was cv. Gedenshirazu-1. These two soybean cultivars were considered to be potential sources of resistance to breed new resistant cultivars with the desirable characteristics of cv. Tanbakuro for this region.