Sources and Genetics of Resistance to Soybean Rust <I>Phakopsora Pachyrhizi (H. Sydow & Sydow)</I> in Nigeria

Abstract

In searching for resistance genes to soybean rust (Phakopsora pachyrhizi (H. Sydow & Sydow), twenty eight soybean genotypes obtained from the International Institutefor Tropical Agriculture (IITA) Ibadan were screened on rust infested field for resistance to rust. These genotypeswere planted at the National Cereals Research Institute (NCRI), Yandev station in Benue State, Nigeria during 2007 and 2008 cropping seasons. Soybean rust is known to be endemic to the Yandev station. Field observations revealed significant variation among the soybean genotypes to rust. Seven soybean genotypes were identified to be resistant to rust which were TGx1987-62F, TGx1935-3F, TGx1951-3F, TGx1936-2F, TGx1987-10F, TGx1972-1F and TGx1949-8F. Genetic analysis of the parental materials after hybridization for the mode of inheritance indicated that rust resistance in soybean was monogenically controlled by dominant genes. The relationship among the resistance genes was established through allelic testing which indicated that genes in TGx1972-1F and TGx1987-10F are allelic and independent of the dominant resistance genes of TGx1951-3F, TGx1936-2F, TGx1987-62F and TGx1935- 3F which are also allelic. The results revealed that dominant alleles at three loci conditioned resistance to soybean rust races found in Nigeria and the tentative symbols formulated for the three loci controlling resistance to rust in soybean were Rsbr1, Rsbr2 and Rsbr3 (Resistance to soybean rust )