Registration of an Induced Tetraploid Sunflower Genetic Stock Line, Tetra P21

A TETRAPLOID SUNFLOWER (Helianthus annuus L.) genetic stock line, Tetra P21 (Reg. no. GS-1, PI 559480) was developed cooperatively and released by the USDA-ARS and the North Dakota Agricultural Experiment Station, Fargo, ND, in December 1990. Tetra P21 was derived from colchicine-treated P-21 VR1, a nuclear male-sterile line selected from P-21 ms, both were released by the USDA and the Texas Agricultural Experiment Station in 1970. Seedlings of P21 VR1 (two true-leaf stage) were inverted and submerged in 0.15% colchicine solution for 5 h in the dark. Heads with doubled chromosome numbers were identified by reduced pollen stainability, larger pollen grains, and larger disk florets. Putative tetraploid, male-fertile heads were selfor sib-pollinated. The resulting tetraploids (2n = 4x = 68) plants selected from the initial population were selfor sib-pollinated to produce sufficient seed for release. Chromosome stability, meiotic chromosome pairing, pollen stainability, and seed set of Tetra P21 have been previously reported (1). P-21 VR1 and Tetra P21 are phenotypically identical, except for the larger disk florets in Tetra P21. Tetra P21 is self-compatible, has 47% pollen stainability, and averaged eight seeds per head upon selfor sib-pollination. Seeds of Tetra P21 are black with a few gray stripes, and have a 1000-seed weight of 66 g. Tetra P2rhas reduced meiotic chromosome pairing and has been cytologically less stable than the diploid P-21 VR1 progenitor. Progenies of Tetra P21 segregate with =75% tetraploid plants (2« = 68), and 25% aneuploids (2n = 67, and 2n = 65 to 70). Tetra P21 will facilitate studies on the effects of polyploidy, production of aneuploids, and evaluations of chromosome doubling on interspecific crossability. Limited quantities of seed of Tetra P21 are available from the Seedstocks Project, Dep. of Crop and Weed Sciences, North Dakota State University, Fargo, ND 58105.