Drought resistance of the new alfalfa line NXNKY05 and ‘Gannong 6’ variety during germination

To determine the drought resistance of the new alfalfa (Medicago sativa) line NXNKY05 and the drought-resistant variety ‘Gannong 6’ during the germination period, we simulated drought stress conditions using different concentrations (0%, 5%, 10%, and 15%) of polyethylene glycol 6000 (PEG-6000) solution, and assessed the following indices: germination potential, germination rate, germination index, vigor index, relative germination potential, relative germination rate, relative germination index, relative vigor index, germination drought index, promptness index, germination stress index, root length, seedling length, fresh weight, and dry weight. The drought resistance of the two alfalfa materials was comprehensively evaluated based on correlation analysis and affiliation function. The results revealed that the germination rate, vigor index, relative germination rate, relative vigor index, and root length of the two alfalfa species tended to initially increase and subsequently decline in response to an increase in PEG-6000-induced stress, whereas in contrast, we recorded reductions in the germination potential, germination index, relative germination potential, relative germination index, promptness index, germination drought tolerance index, germination stress index, seedling length, and seedling fresh and dry weights with increasing PEG-6000 stress. Correlation analysis indicated that germination rate, relative germination rate, germination potential, relative germination potential, germination index, relative germination index, promptness index, germination drought tolerance index, germination stress index, seedling length, and fresh weight could be used as reliable indices for identifying the drought tolerance of alfalfa seeds during the germination period. Moreover, on the basis of our comprehensive evaluation, we established that compared with that of ‘Gannong 6’, NXNKY05 is characterized by a superior resistance to drought.