RESUMO
Random amplified polymorphic DNA technology was used to analyze the genetic diversity of 25 salt-tolerant alfalfa varieties using 30 different primers. Results showed that the percentage of polymorphic loci between single-plant DNA was 81.52%, and that between mixed DNA of various varieties was 61.65%. Compared to the mixed DNA samples, single-plant DNA samples can better reveal the level of genetic variation among and between alfalfa varieties. The gene differentiation coefficients of 18 Chinese salt-tolerant alfalfa varieties and 7 American salt-tolerant alfalfa varieties were 0.271 and 0.152, respectively, showing that the exchange of genes between Chinese salt-tolerant alfalfa germplasms was more frequent than that of American germplasms. As a topical cross-pollinated plant, the genetic structure of biological populations of alfalfa was directly linked to its breeding system. According to the analysis of genetic distance (GD), 25 varieties can be divided into 9 groups, among which, the GD of Tumu No. 1 and Tumu No. 2 was the shortest (0.148), and the GD of Jieda No. 1 and Tumu was the longest (0.786). The analysis of genetic diversity of salt-tolerant alfalfa germplasms provided a theoretical basis for the creation of an alfalfa salt-tolerant core germplasm repository and for the selection and breeding of new salt-tolerant varieties.
Assuntos
DNA de Plantas , Variação Genética , Medicago sativa/genética , Plantas Tolerantes a Sal/genética , Melhoramento Vegetal , Técnica de Amplificação ao Acaso de DNA PolimórficoRESUMO
OBJECTIVE: To compare the efficacy of injections of 1.2 million units of benzathine penicillin G given every 3 weeks versus every 4 weeks for secondary prevention of rheumatic fever, based on the long-term outcome of patients receiving such prophylaxis. METHODS: A total of 249 consecutive patients with rheumatic fever, randomly assigned to either a 3-week or a 4-week regimen, were examined every 3 to 6 months, and followed for 794 and 775 patient-years, respectively. RESULTS: Compliance with each regimen was comparable: 83 (66.9%) of 124 patients in the 3-week group versus 92 (73.6%) of 125 patients in the 4-week group stayed in the program (p > 0.05). Streptococcal infections occurred less frequently in those receiving the 3-week regimen: 7.5 versus 12.6 per 100 patient-years (p < 0.01). Prophylaxis failed in 2 patients receiving the 3-week regimen and in 10 receiving the 4-week regimen (0.25 and 1.29 per 100 patient-years respectively; p = 0.015). Serum penicillin levels were adequate (> or = 0.02 micrograms/ml) in 100 (56%) of 179 samples obtained 21 days after penicillin injection in the 3-week regimen, and in 51 (33%) of 155 samples obtained 28 days after injection in the 4-week regimen (p < 0.01). Of 71 patients with mitral regurgitation in the 3-week regimen, 47 (66%) no longer had the murmur; of 87 patients in the 4-week regimen, 40 (46%) no longer had the murmur (p < 0.05). CONCLUSIONS: This 12-year controlled study indicates that the outcome of patients with rheumatic fever is better with a 3-week than with a 4-week penicillin prophylaxis regimen. Greater emphasis and more widespread use of the 3-week regimen should be recommended.