Effects of nodulation on resistance to alfalfa sickness among ten alfalfa cultivars |
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Authors: | Geok-Yong Tan Wai-Koon Tan |
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Institution: | (1) Plant Science Department, University of Alberta, Edmonton, Canada;(2) Present address: c/o Lowlands Agri. Expt. Station, Cocoa Industry Board of PNG, Keravat, East New Britain, Papua New Guinea |
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Abstract: | Summary Ten alfalfa cultivars were used to study the effects of nodulation and variations in resistance to alfalfa sickness. The alfalfa
seedlings were planted in sick soil with three treatment,,i.e.: pasteurized sick soil inoculated with Rhizobium ‘Nitragin’ which served as the control, the inoculated non-pasteurized sick
soil and the non-inoculated non-pasteurized sick soil. None of the alfalfa cultivars were immune from the sickness. Cultivar
‘Anik’ fromMedicago falcata was among the most resistant cultivars. Three Phytophthora root rot resistant cultivars including ‘Agate’, ‘Apollo’ and ‘Ramsey’
were not resistant to the disease. Alfalfa inoculated with Rhizobium showed greatly improved seedling growth. Correlation
coefficients showed that those alfalfa cultivars more resistant to alfalfa sickness produced more dry weight. Dry weight increase
due to nodulation (82%) had more than compensated for the loss of dry weight due to alfalfa sickness (33%). The present study
suggested that the poor growth of alfalfa on sick soil was attributed to both the soil borne pathogens and the poor nodulation
of alfalfa, probably due to the absence of effective Rhizobium in sick soil. Highly significant differences were also obtained
among olfalfa cultivars for plant dry weight in the inoculation treatment. Selection for effective Rhizobium strains and for
alfalfa genotypes which are resistant to alfalfa sickness and are high in nitrogen fixation rates could improve alfalfa yield
in sick soil. |
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Keywords: | Alfalfa Alfalfa sickness Nodulation Rhizobium |
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