Assessment of techniques for screening alfalfa cultivars for aluminum tolerance

Screening toxicity tests are an effective method to characterize aluminum tolerant plants. In this paper, three screening procedures were used to assess aluminum tolerance among 13 cultivars of alfalfa (Medicago sativa L.). The procedures used were: Petri dish screening, black glass plot method and the soil-on-agar procedure. Major biological indices used to analyze aluminum tolerance were relative root length (RRL), relative germination rate (RGR), relative hypocotyl length (RHL), relative fresh weight (RFW) and root emergence (RE). Aluminum negatively affected all five indices. A Pearson correlation test indicated that the results of the three screening procedures were consistent, suggesting that all three could be used for screening purposes. However, because of the short test period and the simplicity of operation, the black glass plot method might be the best choice. Overall, cv. Super No. 7 and WL-525HQ were the most aluminum-tolerant alfalfa cultivars, while Pondus S was the most sensitive.