Registration of a Powdery Mildew Resistant Sunflower Germplasm Pool, PM1

THE powdery mildew resistant sunflower (Helianthus annuus L.) gerrnplasm pool, PM1, (Reg. no. GP-94) (PI 518661) was developed cooperatively by USDA-ARS and the North Dakota Agricultural Experiment Station, Fargo, ND, and released in September, 1987. PM1 was derived from interspecific hybridization between H. debilis Nutt. and H. annuus L. Genotypes highly resistant to powdery mildew have not been reported in sunflower. PM1 was derived by bulking equal amounts of BC2F2 seeds of three rows of BC2Pi plants having the parentage P-21/3/ H. debilis/P-2l// 'Peredovik'. The multiple-headed H. debilis parent, PI 435667 was highly resistant to sunflower powdery mildew (incited by Erysiphe cichoracearum DC.), when compared with infection in single-headed cultivated H. annum. P-21 is a reselection from Peredovik, and carries a recessive gene for male sterility. In greenhouse evaluations, both P-21 and Peredovik are highly susceptible to powdery mildew. Detailed descriptions of the gene transfer and its inheritance have been reported by Jan and Chandler (1). Their greenhouse evaluations indicated the mean infection percentage, measured as the percent of leaf surface covered by mildew, of P-21, P-21/PI 435667, and PI 435667 were 100, 15 and 0, respectively. Resistance was partially dominant in the F, and backcross progenies and was suggested [Jan and Chandler, (1)] to be under the control of one or a few major gene(s). Initially, two highly resistant F, plants of H. debilis X P-21 were identified and backcrossed to Peredovik. Three highly resistant BC,F, plants were selfpollinated or sibpollinated and three BC,F2 plants having zero infection were identified. These plants were used to pollinate P-21. The resulting BC2F, families, heterozygous for powdery mildew resistance, were sibpollinated and equal amounts of seed from each family were bulked to form the gerrnplasm pool PM1. PM1 has 87.5%cultivated//, annuusand 12.5%H. debilis nuclear genes in normal P-21 cytoplasm. It contains the partially dominant powdery mildew resistance gene(s) at a frequency of approximately 50%. It also contains a recessive genetic male-sterility gene, derived from P-21, at a frequency of approximately 50%. Even though PM1 is still heterogeneous and is expected to segregate for certain traits, most plants are of the cultivated type with a plant height of 1.7 m, single-headed and selfcompatible. Seeds are either black or black with white stripes, and have a 1 000 seed weight of 57g. Limited quantities of seeds are available from the Seedstocks Project, Agronomy Department, North Dakota State University, Fargo, ND 58105.