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Inheritance of resistance of soybean [Glycine max (L.) Merrill] to races 4 and 15 of frogeye leaf spot fungus (Cercospora sojina Hara)

Carlos Alberto Arrabal Arias^I; José Tadashi Yorinori^II; José F. Ferraz de Toledo^II; Romeu A.S. Kiihl^II

^IDepartamento de Biologia Geral, Universidade Estadual de Londrina, Caixa Postal 6001, 86055-900 Londrina, PR, Brasil. Send correspondence to C.A.A.A.
^IICentro Nacional de Pesquisa de Soja (CNPSo-EMBRAPA), Rodovia Carlos João Strass, Acesso Orlando Amaral, Caixa Postal 1061, 86001-970 Londrina, PR, Brasil

ABSTRACT

Frogeye leaf spot caused by Cercospora sojina is one of the most important soybean diseases in Brazil and has caused severe losses in many regions. The development of new cultivars resistant to C. sojina is a priority in all breeding programs, since it is the most efficient and economical control method. Although more than 20 races of C. sojina have been identified, the genetic control of resistance to this pathogen is largely unknown. To determine the inheritance of the resistance of soybean to races Cs-4 and Cs-15 of C. sojina, crosses between cultivars Davis, S. Rosa (Santa Rosa), BR-27 (Cariri), Paraná and Bragg were made and quantitative and qualitative analyses applied to the data. There are three distinct alleles for resistance to race Cs-4, one in Davis (Rcs^a₃), one in Paraná (Rcs^b₃) and a third in S. Rosa and BR-27 (Rcs^c₃), which independently determine resistance. The two alleles Rcs^a₃ and Rcs^b₃ also confer resistance to race Cs-15. Additional genes for resistance to Cs-4 appeared in the crosses S. Rosa x Bragg, S. Rosa x BR-27 and Paraná x Bragg, and to Cs-15 in the crosses Davis x S. Rosa and Davis x Bragg, but these are not the sole determinants of resistance. A progeny test must be performed to confirm these results.

Keywords: soybean; frogeye leaf spot; fungus.

REFERENCES

Arias, C.A.A. (1991). Herança da resistência da soja (Glycine max) às raças 4 e 15 de Cercospora sojina. Master's thesis, Universidade Estadual de Londrina, Londrina, PR, Brasil, pp. 170.

Arias, C.A.A., Toledo, J.F.F. and Yorinori, J.T. (1994). An improved procedure for testing theoretical segregation models in qualitative genetic studies of soybeans. Rev. Bras. Genet. 17: 291-297.

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Toledo, J.F.F. (1986). The biometrical studies of inbred lines and their hybrids. Doctoral thesis. The University of Birmingham, Birmingham, pp. 139.

Veiga, P. (1973). Cercospora sojina Hara: obtenção de inóculo, inoculação e avaliação da resistência em soja [Glycine max (L.) Merrill]. Master's thesis. ESALQ, USP, Piracicaba, SP, pp. 32

Yorinori, J.T. (1988). Determinação de raças de Cercospora sojina. In: Resultados de Pesquisa de Soja 1986/87. Empresa Brasileira de Pesquisa Agropecuária, Centro Nacional de Pesquisa de Soja, Londrina, PR, Brazil, pp. 174, 180-181.

Yorinori, J.T. (1989). Frogeye leaf spot of soybean (Cercospora sojina Hara). In: World Soybean Research Conference - IV, March 5-9. Vol. III. Buenos Aires, Argentina, pp. 1275-1283.