found a regression relationship between canola seed yield and precipitation from 21 June to 20 August and Canola (Brassica napus L.) yield is often limited by heat and water mean daily temperature from 15 June to 15 August. The stress. Early seeding may avoid the heat and water stress at critical regression equations indicated that for each millimeter growth stages but will encounter low soil temperatures and frequent increase in precipitation, the yield of canola increased frosts. Three experiments were performed at two locations in Montana by 5.9 kg ha Ϫ1 . Also, for each degree rise in mean daily from 2002 to 2004 to determine (i) early spring seeding effect on seed temperature, there was a corresponding yield reduction yield and oil content and optimum seeding rates for early seeding, (ii) base temperature (T b ) for germination and heat requirement for of 188 kg ha Ϫ1 . In dryland cropping systems, water is emergence, and (iii) suitable cultivars for early spring seeding. Late-the most limiting factor for crop production. In a review March-seeded canola yielded 0 to 5% greater than mid-April seeding. paper, Johnston et al. (2002) suggested that a minimumDelaying seeding from mid-April to mid-May resulted in 43 to 63% of 127 mm of water is required for canola seed producyield reduction. Oil content was 12 to 22 g kg Ϫ1 greater for mid-May tion in the northern Great Plains. After the minimum seeding than mid-April seeding in 3 out of 5 site-year combinations.water requirement is met, canola produces 6.9 to 7.2 A seeding rate of 32 to 65 seeds m Ϫ2 was found sufficient to produce kg ha Ϫ1 of seed for every millimeter of precipitation optimum yields. Oil content tended to decrease 10 to 20 g kg Ϫ1 when consumed. Canola has a tap root system that can extract seeding rate increased from 11 to 97 seeds m Ϫ2 . The T b for germination water from a soil depth of 1.1 to 1.7 m (Nielsen, 1997). In was less than 4؇C, and the growing degree days for 50% emergence shallow soils that have a limited water-holding capacity, (GDD 50 ) were 42 to 81. Yield was negatively correlated (r ϭ Ϫ0.46 such as the Judith clay loam (fine-loamy, carbonatic to Ϫ0.65) to the days to 50% flowering, and biomass measured at Typic Calciborolls) in central Montana, canola may have 60 d after planting was negatively correlated to the chlorophyll fluores-to rely on frequent rainfall to sustain growth and procence ratio (F v /F m ) after cold stress (r ϭ Ϫ0.58). The optimal seeding duce seed during the latter part of the growing season.period for the region is between late March and mid-April. Several genotypes were found to have favorable characteristics for early Precipitation timing and amount vary greatly year to seeding.year and location to location in Montana. Consequently, growers in the region encounter highly unstable canola yields.

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Utilization of the doubled haploid method of breeding usually shortens the time to cultivar release, and methods of haploid production need evaluation in a breeding programme. Thirty-eight different threeway crosses were tested for anther culture response. On average 5.8 percent of the anthers cultured produced calli. Three crosses were found recalcitrant for callus induction. Overall, the anther culture method produced 0.6 plantlet per 100 anthers cultured. Five crosses with an average of 5.8 and 2.8 percent of anthers producing calli and plantlets, respectively, were compared using anther culture and wheat X maize crosses. Non-responsive genotypes for callus induction and plantlet formation in the anther culture method proved to be good parental material in wheat X maize crosses. The average percentages of embryo formation and plantlet production in wheat X maize crosses were 10.3 and 4.7, respectively. Anther-derived plants were cytologically unstable, whereas all the plants regenerated from wheat x maize crosses were haploids (n = 21 chromosomes). The chromosome numbers of the polyhaploids were doubled with a colchicine treatment. Improvement of the two haploid production methods to facilitate their efficient use in a breeding programme is discussed.

This study describes the development of a highly repeatable cold screening procedure for lentil (Lens culinaris Medik.) using controlled conditions which involve first, acclimation of the plants at the vegetative stage in a growth chamber and second, freeze testing in a freeze chamber. The seeds were first germinated in Petri dishes and then planted in styrofoam trays with individual cells. Initial growing temperatures in the growth chamber for two weeks were 25 °C day and 10 °C night with a 12 h photoperiod. In the third week the photoperiod was changed to 10 h and in the fourth the temperatures were changed to 10 °C day and 0 °C night to acclimate the plants. Using a modified freeze chamber (household deep freezer), a freeze test temperature of −15 °C, following a 6–8 weeks acclimation period (because both acclimation times had the same effect for cold tolerance of the genotypes), at 2 and 3 °C/h cooling rate, and an exposure time of 3 h at −15 °C were appropriate to detect significant (P<0·01) differences among several lines at a comparatively low degree of injury for the most cold-hardy genotypes.

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