Rhigoctaia so&& was found able to grow 0s a saprophyte through natural unsterilized soil. Its rate of growth under different soil conditions in glass tumblers was studied by the Rossi-Cholodny soil-plate method. Growth was most rapid at the lowest soil-moisture content tested, viz. 30 yo saturation, and was accelerated by for& aeration of the soil. The maximum distance to which mycelial growth could be suppofied on the food reserves of the agar inoculum alone was some 5 ~n . , as shown by extent of growth through tubes of moist sand, but in 23 days the fungus grew 21-24 crn. through tubes of soil. Removal of the agar disk 2 days after inoculation of the tubes reduced growth through sand by more than half, but through soil by only a small proportion. In soil, Rhizoctonk was able to cause 100% darnping-off of radish seedlings planted at a radial distance of 4 un. from the agar inocdum, and some 40 yo darnping-off at a distance of 9 an. The depressing effect of additions of I % ground-wheat straw or dried grass to the soil upon growth of the fungus was attributed to (I) the negligible cellulosedecomposing ability of Rhizoctoniu, (2) nitrogen starvation of the mycelium, through rapid utilization of the available soil nitrogen by the cellulose-decomposing micro-organisms multiplying upon the fresh organic material, (3) fungistatic action on Rhizoctonia of the respiratory carbon dioxide produced by the cellulose-decomposers.

No abstract

The development of Eryszphe graminis f. tritici Em. Marchal, from spore germination to spore formation, occupied 6 days and ascospore discharge in the field covered a period of I month. On immune hosts development of the fungus generally ceased at the point of invasion of cell cytoplasm. The features of host plant resistance have been discussed.Lithium chloride soil applications were made as 0.8% solution in glasshouse seedling plant experiments and at 56 lb./acre rate in a factorial field trial. In the former, mildew was reduced from I I % leaf area infected to I % , but under field conditions only from 1-29 to 1.04% over two sampling periods. The limiting effects of lithium on mildew began to decline 18 weeks after soil treatment.Race 4 of E . gramirris f. tritici (Canadian typing) was present in all, and Race 3 in about half the New Zealand wheat localities during 1948-9. The infection types of Races 3 and 4 on 180 wheat varieties and breeding selections have been recorded, and the basis for a mildew resistance plant-breeding programme is discussed, including consideration of adult plant resistance.

Detection of bacteria other than Rhizobium in nodule cultures led to studies on bacteria existing within normal clover roots. Those isolated from clover root tissue appeared to fall into five groups on the basis of morphology and biochemical characteristics. The identity of three of the groups was tentatively established respectively as Aerobaclcr cloacae Jordan, Bergey et al., Bacillus megatherium De Bary, and Flavobacterium rhenanus (Migula) Bergey et al.

l1he Rhizobium content af cammercial inaculant;; has been increased since the time these preparatians were intraduced to' replace the formerly used agar cultures.Regardless of the presence of ather arganisms, the powder inaculants now in use are effective in lucerne nodulation and nitrogen fixaJtion.NO' benefit was demonstrated in favour af disinfectian af lucerne seed priar to' inoculatian, while in seed pelleted with lime there was a decline in the survival of rhizabia aver a 3-months' periad.In a number of soils where lucerne establishment in the past has failed it has been shawn that indigenous lucerne rhizabia (Rhizobium meliloti) were absent ar ineffective, in sharp cantrast with the abundance and nodulation efficacy af Rhizobium trifolii an subterranean claver. In some of these soils lucerne was established by the inaculation of seed with effective rhizabia, aided by raising the sail pH with lime applicatians and ~he use af inaculated seed, pelle ted with lime ar magnesium.Among seven varieties af lucerne different responses were obtained to' inoculatian wi~ single strains of R. meliloti, but the use af multistrain commercial cultures achieved satisfactary nodulatian and grawth of ~hese varieties.