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Dep. of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078
* Corresponding author (jlc{at}mail.pss.okstate.edu)
OK 190 alfalfa (Medicago sativa L.) germplasm (Reg. no. GP-346, PI 619203), was released by the Oklahoma Agricultural Experiment Station in 2000. OK 190 provides a unique combination of a broad genetic base, pest resistance, and production potential needed in alfalfa for the southern Great Plains. This germplasm is the result of the interpollination of 579 plants derived from the convergence of three lines of pest resistance breeding, that is, resistance to the blue alfalfa aphid (Acyrthosiphon kondoi Shinji), spotted alfalfa aphid [Therioaphis maculata (Buckton)], and Phytophthora root rot (caused by Phytophthora megasperma Drechs. f. sp. medicaginis T. Kuan & D.C. Erwin.). Source populations screened in the greenhouse for resistance to the blue alfalfa aphid, collected in Oklahoma prior to 1990 (Zarrabi et al., 1994), included ‘Aggressor’ (North American Alfalfa Improvement Conference, 2000), ‘Apollo Supreme’, ‘Arrow’, ‘Cimarron’ (Plant Variety Protection No. 7900092), ‘Cimarron VR’, ‘CUF 101’ (Lehman et al., 1983), ‘Garst 630’, ‘OK 169’ (Caddel et al., 2002), ‘WL 317’ (Kugler et al., 1991), ‘WL 320’ (Hanson et al., 1987), ‘WL 322 HQ’ (Huset et al., 1991), ‘555’ (Woodward and Miller, 1989), ‘5472’ (Woodward et al., 1993), and three experimental populations. Source material screened in the greenhouse for resistance to the spotted alfalfa aphid included Aggressor, Apollo Supreme, Arrow, ‘Baker’ (Kehr et al., 1978), Cimarron VR, CUF 101, ‘Good As Gold’, OK 169, WL 317, WL 320, WL 322 HQ, 555, and three experimental populations. Material screened in the field for resistance to Phytophthora root rot included Cimarron, WL 320, WAPH-1 (Grau, 1992) germplasm, and two experimental populations. From these three breeding lines, a total of 579 plants were transplanted to an isolated field and interpollinated with honey bees (Apis mellifera L.) to produce syn 1 seed. The plants traced to approximately 25% 555, 18% experimental populations, 8% each Cimarron and WL 320, 7% CUF 101, and 5% each Arrow and OK 169. Other cultivars contributed less than 4% each to the population.
Seedling tests to evaluate resistance (North American Alfalfa Improvement Conference, 1999) to blue alfalfa aphid and spotted alfalfa aphid were conducted at Stillwater, OK. The percentages of seedlings exhibiting resistance after infestation with aphids collected in Oklahoma were blue alfalfa aphid—OK 190 = 13, CUF 101 (R) = 25, and ‘Arc’ (S) = 6; spotted alfalfa aphid—OK 190 = 55, Baker (R) = 50, and ‘Caliverde’ (S) = 2 [(R) = Resistant; (S) = Susceptible].
On the basis of its parental sources, OK 190 also should provide resistance to bacterial wilt [caused by Clavibacter michiganensis subsp. insidiosus (McCulloch)]; Verticillium wilt, (caused by Verticillium albo-atrum Reinke & Berthier), Fusarium wilt [caused by Fusarium oxysporum Schlechtend.: Fr. f. sp. medicaginis (Weimer) W.C. Snyder & H.N. Hans], anthracnose (caused by Colletotrichum trifolii Bain & Essary), Phytophthora root rot, and pea aphid [A. pisum (Harris)]; and a low or moderate level of resistance to alfalfa stem nematode [Ditylenchus dipsaci (Khn) Filipjev] and Aphanomyces root rot [caused by Aphanomyces euteiches Drechs].
Flower color of OK 190 is predominately purple (>95%) with some variegated flowers and a trace of white and yellow flowers. Fall dormancy of OK 190 is similar to ‘Legend’, approximately 4 (1–9 scale, where 9 is very non dormant). Winter hardiness has been sufficient for the germplasm to survive several winters in Oklahoma. Forage yield potential for OK 190 has been tested since 1995 in several Oklahoma sites. Each trial included the best cultivars developed by public and private breeding programs. Detailed results of each forage evaluation have been distributed in Central Alfalfa Improvement Conference Variety Test Reports and are available online at www.agr.okstate.edu/alfalfa/var-test/alf-var.html; verified 10 Dec. 2001. Yields of OK 190 have been good, but not as consistently highly productive as the best cultivars for the area.
Twenty grams of syn 3 seed will be provided upon written request to the corresponding author and agreement to make appropriate recognition of its source when this germplasm contributes to the development of a new germplasm, cultivar, hybrid, or strain cross. Request for seed from outside the USA should be accompanied by the appropriate customs and control documents.
NOTES
Contribution from the Oklahoma Agric. Exp. Stn. Registration by CSSA.
Accepted for publication October 31, 2001.
REFERENCES
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