In vitro microspore mutagenesis and selection was used to produce five fertile double-haploid imidazolinone-tolerant canola plants. The S2 plants of three of the mutants were resistant to at least the field-recommended levels of Assert and Pursuit. One mutant was tolerant to between five and ten times the field-recommended rates of Pursuit and Scepter. Two semi-dominant mutants, representing two unlinked genes, were combined to produce an F1 hybrid which was superior in imidazolinone tolerance to either of the heterozygous mutants alone. Evaluation of the mutants under field conditions indicated that this hybrid and the original homozygous mutants could tolerate at least two times the field-recommended rates of Assert. The field results indicated the mutants were unaffected in seed yield, maturity, quality and disease tolerance. These genes represent a potentially valuable new herbicide resistance system for canola, which has little effect on yield, quality or maturity. The mutants could be used to provide tolerance to several imidazolinones including Scepter, Pursuit and Assert.

1979. The early morphogenesis of Glycit~~mcix and Pislit~l scitiurrm root nodules. Can. J. Bot. 57: 2603-2616. The development of preemergent and early emergent stages of soybean (Glycine tncis) and garden pea (Pisurn scitic~rnl) root nodules has been studied utilizing the superior preservation and resolution obtained by noncoagulative fixatives and subsequent embedding in plastic. In both species, extensive mitotic activity and cytological changes occur in the root cortical cells while the infection thread is restricted to the infected root hair cell. In soybean the central mass of infected tissue is derived mainly from the outer layer of cortical cells whereas the inner cortical cells contribute extensively to the infected tissue of the pea nodules. The temporal and spatial patterns of mitosis differ in the nodules ofthe two species. Mitotic activity is restricted to a nodule rneristern and occurs over a period of many weeks in pea nodules. In soybean nodules, mitotic activity occurs throughout the central zone and before decreasing, persists over a period of a few weeks. The timing and distribution of mitotic activity affects nodule rnorphogenesis. NEWCOMB, W., D. SIPPELL et R. L. PETERSON. 1979. The early rnorphogenesis of Glycine tnax and Pisrrtn satiolrtn root nodules. Can. J. Bot. 57: 2603-2616. Les auteurs ont etudie le developpernent des stades de pre-emergence et de debut d'lrnergence des nodules racinaires du soja (Glycine max) et du pois (Pisrrt~l sci~iuutn), en utilisant les avantages d'une conservation et d'une resolution superieures obtenues grHce a I'utilisation de fixatifs non-coagulants avant I'enrobage dans le plastique. Chez les deux espkces, d'irnportants changernents surviennent dans I'activite cytologique et rnitotique au niveau des cellules du cortex racinaire alors que le cordon d'infection ne se retrouve que dans le poi1 absorbant infect&. Chez le soja, la rnasse centrale de tissus infectes provient surtout des couches les plus externes des cellules corticales alors que les cellules corticales internes contribuent beaucoup aux tissus nodulaires infectes chez le pois. Le patron spatial et ternporel des mitoses diffkre chez les nodules des deux especes. L'activite rnitotique est restreinte a un rneristeme nodulaire et s'effectue au cours d'une periode de plusieurs sernaines chez le nodule du pois. Quant au nodule du soja, I'activite rnitotique a lieu a travers toute la zone centrale et, avant de decliner, persiste pendant une periode de quelques sernaines. La chronologie et la distribution de I'activite mitotique affecte la rnorphogentse du nodule.[Traduit par le journal]

No abstract

No abstract

No abstract

No abstract

No abstract

No abstract