• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.4
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• pp.239-244
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• 1998

Susceptibility of soybean cultivars to Calonectria illicicola was evaluated in a greenhouse by inoculating seedlings with mycelium in agar discs placed on the stems at the soil line. A range of responses was detected among cultivars following inoculation with a virulent isolate of C.ilicicola. Rankings of cultivars between greenhouse tests 1 and 2 were similar for disease severity and areas under the disease progress curves (AUDPC). In addition, rankings of cultivars for Final disease severity were highly correlated with AUDPC in test 1 ($r_s$ =0.88, t =5.48, p<0.001), test 2 ($r_s$ =0.99, t =22.10, p<0.001), and when tests were combined ($r_s$=0.89, t=5.82, p<0. 001). Final disease severity and AUDPC consistently identified Asgrow 7986, Braxton, Cajun, and Forrest as soybean cultivars least susceptible to red crown rot. In 1993 and 1994 field tests, a range in disease susceptibility was observed for tested cultivars but none was completely resistant. Soybean cultivars Braxton, Cajun, and Forrest, which were least susceptible to red crown rot in greenhouse tests, also ranked among cultivars with the lowest disease incidence and AUDPC in field tests. Comparisons .between rankings of the eight cultivars common to greenhouse and field tests showed a correlation between final disease severity from combined greenhouse tests and both final disease incidence ($r_s$=0.63, t =1.99, p<0.1) and AUDPC ($r_s$=0.60, t =1.82, p < 0.2) from the combined field tests. However, AUDPC from greenhouse tests did not correlate with either final disease incidence or AUDPC from field tests. The green-house screening method provided consistent results between greenhouse and field tests and successfully identified the least susceptible cultivars Braxton, Cajun, and Forrest.

• Korean Journal Plant Pathology
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• v.14 no.6
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• pp.571-577
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• 1998

Variability in virulence of Calonectria ilicicola isolates form different hosts and geographic origin provides important information for breeding cultivars resistant to red crown rot. A wide range in virulence for 25 isolates of C. ilicicola from soybean and peanut was observed on six soybean cultivars. Soybean isolates were pathogenic on soybean although some were less virulent. Virulence of isolates was not affected greatly by cultivar and relatively consistent regardless of virulence level. Soybean isolates were more virulent on soybean than were peanut isolates. When virulence of two soybean and tow peanut isolates was compared between laboratory and greenhouse tests, it was stable across a range of cultivars. Mycelial growth of isolates from either soybean or peanut was reduced significantly on potato dextrose chlorate showed significant reduction of fungal growth than isolates from peanut did although their growth on potato dextrose agar was not significantly different. Evidence for physiologic specialization was not recognized in this system. However, the findings that soybean isolates of C. ilicicola were more virulent on soybean and reduction of fungal growth on potato dextrose chlorate than were peanut isolates suggest that host specialization may exist in this fugus.

• The Korean Journal of Mycology
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• v.26 no.3 s.86
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• pp.387-395
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• 1998

Mycelial growth, production of microsclerotia and perithecia, and presence of double-stranded RNA were examined in Calonectria ilicicola isolates from several hosts to detect morphological and/or genetic markers for comparison with levels of virulence. Variability in disease severity, production of microsclerotia and perithecia, and mycelial growth was observed across all isolates. None of 35 isolates of C. ilicicola examined contained detectable levels of double-stranded RNA. Disease severity on soybean cultivars correlated positively with production of both microsclerotia and perithecia. Mycelial growth correlated negatively with production of perithecia. Virulence on the cultivars and production of microsclerotia and perithecia were greater in isolates of C. ilicicola from soybean than those from peanut. These results suggest that the ability of isolates to produce microsclerotia and perithecia is a component of inoculum potential. Perithecia production may serve as a useful marker for characterizing virulence or host specialization in this homothallic fungus.

• Research in Plant Disease
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• v.12 no.3
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• pp.178-184
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• 2006

The 18 isolates of soybean red crown rot pathogen(Calonectria ilicicola) were isolated from infected soybean plants showing chlorosis symptom and red perithecia sign in 2002 and 2003 season in Korea. The morphological characteristics of the typical isolate SC03-15, such as macroconidia and macrovesicles in anamorph as well as perithecia, asci and ascospores in teleomorph, were observed from red crown rot pathogens. The perithecia were red-brown globose to ovoid, and $357.9(312.5{\sim}391.5.7){\mu}m$ high and $474.3(419{\sim}535){\mu}m$ diameter. Asci were hyaline and clavate and included 8 ascospores, which were straight to slightly curved, 1(-3)-septate, and $36.9(31.1{\sim}49.4){\times}5.2(4.5{\sim}6.1){\mu}m$. Macroconidia in anamorph were cylindrical, hyaline and in size $73.2(68.1{\sim}77.6){\times}5.8(4.9{\sim}6.8){\mu}m$. Further identification process was performed through molecular method, such as a phylogenetic analysis by rDNA sequencing of ITS and $\beta$-tubuline genes of all isolates tested in this study. All isolates were identified as Calonectria ilicicola by DNA sequencing of ITS and $\beta$-tubuline genes, and morphological characteristics.