No abstract

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.

Alfalfa (Medicago sativa L.) varieties are generally bred as synthetics. The number of selected parents to create a variety is important during breeding, as alfalfa suffers from severe inbreeding depression. In this study, we tested if there was more genetic drift in synthetic populations with fewer parents (i.e., narrow‐based synthetics) as measured by two parameters: a loss of allelic richness and changes in disease resistance. Out of five base germplasms, parents were selected based on plant field vigor to create derived narrow‐based (six‐parent) and broad‐based (56‐ to 86‐parent) synthetics in order to test the new synthetics compared with their base populations for resistance to four diseases: anthracnose, Phytophthora root rot (PRR), Aphanomyces root rot (ARR), and Fusarium wilt (FW). Using simple sequence repeat (SSR) DNA markers, we also calculated allele frequency changes and allele richness for the original populations and the selected parents of the derived synthetics. Based on the DNA markers, we saw strong evidence of greater genetic drift in the narrow‐based selections compared with the broad‐based selections. The narrow selections had greater allele frequency changes and had fewer (11.5–33.9% fewer) alleles compared with the broad selections and original populations. There was only moderate evidence of genetic drift affecting disease resistance. Within some populations, parent number had an effect on anthracnose and FW resistance, but not PRR or ARR resistance. We suspect that because disease resistance is a complex, often multigenic trait in alfalfa, disease resistance is less influenced by genetic drift, particularly compared with neutral DNA markers.

No abstract

REGISTRATION OF 'WL 516' ALFALFA 'WL 516' alfalfa (Medicago saliva L.) (Reg. no. 143) (PI 508279) was developed by W-L Research. It was tested under the experimental designation B-10 and released in September 1985. WL 516 is a 219-clone synthetic cultivar. Parental clones were derived from two experimental cultivars that had exhibited superior persistence and forage yield potential in tests at Bakersfield, CA. The two experimental cultivars were screened for resistance to Phytophthora root rot (caused by Phytophthora megasperma Drechs., f. sp. medicaginis Kuan & Erwin), recombined, and screened for resistance to anthracnose (caused by Colletotrichum trifolii Bain.). Clones contributing to the two experimental cultivars were selected on the basis of three to four cycles of recurrent phenotypic selection that included screening for resistance to one or more of the following: spotted alfalfa aphid [Therioaphis maculata (Buckton)], pea aphid [Acyrthosiphon pisum (Harris)], blue alfalfa aphid [Acyrthosiphon kondoi (Shinji)], Fusarium wilt [caused by Fusarium oxysporum Schlecht f. sp. medicaginis (Weimer) Snyd. & Hans.], and bacterial wilt [caused by Corymb act erium insidiosum (McCull.) H.L. Jens.]. The original germplasm traces primarily to 'Sonora', 'Lahontan', 'Moapa', 'Buffalo', and Kansas Common, with limited contributions from 'Saranac', 'Ranger', and 'Atlantic'. The fall dormancy of WL 516 is similar to 'Moapa 69'. It has high resistance to Phytophthora root rot (superior to MnPD-1), spotted alfalfa aphid (equal to 'CUF 101'), pea aphid (superior to PA-1), Fusarium wilt (equal to Moapa 69), and blue alfalfa aphid (equal to CUF 101); moderate resistance to stem nematode [Ditylenchus dipsaci (Kuhn) Filipjev] and bacterial wilt; and low resistance to anthracnose. WL 516 is a nondormant cultivar adapted for forage use in the southern and southwestern regions of the USA, and in other areas where nondormant cultivars are grown. Essentially all flowers are purple at full bloom, although occasional variants may be observed. 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 516 was reviewed favorably in 1985 by the National Certified Alfalfa Variety Review Board. Seed of WL 516 must be sold by cultivar name only as a class of certified seed, under provisions of U.S. Plant Variety Certificate 8600041.