Onobrychis Species Research Articles

Nodulation and frequencies of wild leguminous species in the northern Negev region of Israel

(1) The nodulation by Rhizobiurn of Old World leguminous range species occurring naturally under semi-desert conditions on soils of medium and lower fertility was assessed for reference to comparable areas in southern Australia and in connection with the development of ley farming practices in dry marginal wheat areas of the Middle East. (2) Nodules were present on all 33 legumes found on three soil associations in a transition zone between the Mediterranean and Irano-Turanian plant geographical territories. All species showed evidence of symbiotic nitrogen fixation; there was great variation between species in that some were uniformly well nodulated, but others were nodulated sparsely and at a low level of effectiveness. (3) In terms of amount and apparent effectiveness of nodulation per plant in spring, species of Lathyrus, Pisum, and Vicia were outstandingly good. A species each of Hymenocarpos and Lotus were well nodulated, and intermediate degrees of nodulation characterized species of Hedysarum, Hippocrepis, another Lotus, Medicago, Onobrychis, Scorpiurus, Trifolium, and Trigonella. Four species of Astragalus, one of Coronilla, and two of Ononis were poorly nodulated in the natural state on these lands. (4) Plants of Trigonella arabica Del. were present at greatest frequency over the three soil associations but species of Trifolium and Medicago were minor components. In terms of volume of active nodule tissue, however, Hymenocarpos circinnatus (L.) Savi was rated best over all soils; Onobrychis crista-galli(L.) Lam. was prominent in this respect in the most arid places.

IX.—Uromyces punctatus Schroet. in Britain

SynopsisOn the European continent, Uromyces punctatus is heterœcious and occurs on 35 species and 1 variety of Astragalus, 6 species of Oxytropis and 1 species of Onobrychis. There are 3 æcidial hosts recorded, the major one being Euphorbia cyparissias. At St Andrews, the uredo stage of the rust is confined to A. danicus and only uredospores and teleutospores have been found. Experiments conducted showed that the local population of the rust was capable of infecting 9 species of Astragalus and 1 species of Medicago, out of 27 species of Astragalus, 5 species of Medicago and 28 species of other legumes inoculated. No host specialization within the local population was evident. Attempts to germinate the teleutospores, using a variety of methods, failed, with the exception of a single spore. The major æcidial host, when inoculated with teleutospores, failed to show any signs of æcidial infection over a period of four years. Possible factors affecting the shortening of the life cycle of the rust are discussed.