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REGISTRATION OF 'WL 605' ALFALFA 'WL 605' alfalfa (Medicago saliva L.) (Reg. no. 145) (PI 508281) was developed by W-L Research. It was tested under the experimental designation B-57 and released in September 1985. WL 605 is a 177-clone synthetic cultivar. Parental clones were selected following a cycle of recurrent phenotypic selection for resistance to the blue alfalfa aphid [Acyrthosiphon kondoi (Shinji)] and one cycle for tolerance to anthracnose (caused by Colletotrichum trifolii Bain.). The component populations had been screened previously for resistance to spotted alfalfa aphid [Therioaphis maculata (Buckton)], Phytophthora root rot (caused by Phytophthora megasperma Drechs. f. sp. medicaginis Kuan & Erwin), and Fusarium wilt [caused by Fusarium oxysporum Schlecht f. sp. medicaginis (Weimer) Snyd. & Hans.]. Source germplasm includes plants selected for resistance to downy mildew (caused by Peronospora trifoliorum d By.) within field plots of two WL experimental cultivars, plus germplasm tracing to 'CUF 101', 'Shiver', and three releases from the University of California, namely, UC 123, UC 143, and A77-10B. The fall dormancy of WL 605 is similar to that of CUF 101, It has high resistance to Phytophthora root rot (superior to MnPD-1), spotted alfalfa aphid (equal to PA-1), Fusarium wilt (equal to 'Moapa 69'), blue alfalfa aphid (superior to CUF 101), and pea aphid [Acyrthosiphon pisum (Harris)] (equal to PA-1); and moderate resistance to stem nematode [Ditylenchus dipsaci (Kuhn) Filipjev]. It is susceptible to anthracnose and bacterial wilt [caused by Corynebacterium insidiosum (McCull.) H.L. Jens.]. WL 605 is a very nondormant cultivar adapted for forage use in the southern USA, particularly in the southern portion of the southwestern region. The flower color is purple (100%) with occasional variants. One generation each of breeder seed (Syn 1), foundation (Syn 2), and certified (Syn 3) seed classes is recognized. Breeder seed was produced under cage isolation at Bakersfield, CA. Sufficient foundation seed was produced in the lower San Joaquin Valley, CA, for the life of the cultivar. A maximum of 3 and 5 harvest yr are permitted on fields producing foundation and certified seed, respectively. WL 605 was reviewed favorably in 1985 by the National Certified Alfalfa Variety Review Board. Seed of WL 605 must be sold by cultivar name only as a class of certified seed, under provisions of U.S. Plant Variety Certificate 8600042.

Diallel cross progenies, including reciprocals, of six alfalfa (Medicago sativa L.) clones that differed in miridinduced leaf malformation and aphid resistance were studied to obtain estimates of combining ability effect for characters associated with resistance to the spotted alfalfa aphid (SAA), Therioaphis maculata Buckton; the peaaphid (PA), Acyrthosiphon pisum Harris; and two mirids: the alfalfa plant bug (APB), Adelphocoris lineolatus Goeze, and the tarnished plant bug (TPB), Lygus lineolaris Beauv. The responses to mirid feeding were measured in the field with controlled APB and TPB infestations under cages. Aphid tests were conducted on seedlings in the greenhouse. The hypothesis that the same genetic system controlled feeding by APB and TPB was supported by the absence of significant genotype ✕ mirid species interactions. Forage yield and stem length were reduced 5 and 20%, respectively, whereas percentages of dry matter were unchanged and protein percentages increased 4% due to mirid infestation. Resistance to mirid‐induced forage yield reduction and stunting was not found. Leaf malformation, a symptom of mirid feeding, appeared to be a highly heritable trait, but was not correlated with forage yield reduction, stunting, forage quality, or aphid resistance. General combining ability effects were far more important than specific combining ability effects among single crosses for forage yield, stem length, and leaf malformation under mirid infestation, and for PA and SAA resistance.

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