. 2004. Canola and mustard response to short periods of temperature and water stress at different developmental stages. Can. J. Plant Sci. 84: 697-704. Seed yield of Brassica crops in semiarid environments can be increased by minimizing the crops' exposure to high temperature and water stress that often occurs during the growing season. A growth chamber study was conducted to determine the effect of short periods of high temperature and water stress at different developmental stages on seed yield and yield components of Brassica crops. Two canola-quality Brassica juncea 'PC98-44' and 'PC98-45', a Brassica napus canola 'Quantum', and a B. juncea oriental mustard 'Cutlass' were grown under 20/18°C day/night temperatures with photoperiod of 16/8 h light/dark. High (35/18°C) and moderate (28/18°C) temperature stress was imposed for 10 d during bud formation, flowering, and pod development. Low (90% available water) and high (50% available water) water stress was imposed in combination with the temperature treatments. On average, the 35/18°C stress reduced main stem pods by 75%, seeds pod -1 25%, and seed weight 22% from the control. Seed yield per plant was reduced by 15% when plants were severely (35/18°C) stressed during bud formation, 58% when stressed during flowering, and 77% when stressed during pod development. Plants stressed at earlier growth stages exhibited recovery, whereas stress during pod development severely reduced most of the yield components. Effect of water stress on seed yield was minimal regardless of crop developmental stage. The four Brassica cultivars responded similarly to water stress. In response to temperature stress, B. juncea produced greater number of pods per plant but had a great rate of pod infertility than B. napus. Seed yield of B. juncea in semiarid environments can be increased by improving pod fertility, whereas the seed yield of B. napus can be increased by improving pod production and retention. On peut accroître le rendement grainier des espèces du genre Brassica en milieu semi-aride en réduisant le plus possible l'exposition des plantes aux températures élevées et au stress hydrique fréquents durant la période végétative. Les auteurs ont effectué une expérience en phytotron afin de préciser les conséquences de brefs stress thermique et hydrique à divers stades de croissance sur le rendement grainier et sur divers paramètres du rendement des espèces du genre Brassica. Pour cela, ils ont cultivé deux variétés de Brassica juncea de qualité canola (PC98-44 et PC98-45), le canola (B. napus) Quantum et la moutarde joncée (B. juncea) Cutlass à la température diurne/nocturne de 20/18°C durant une photopériode de 16/8 h de clarté/obscurité. Ils ont ensuite soumis les plantes à un stress thermique intense (35/18°C) ou modéré (28/18°C) pendant 10 jours lors de la formation des bourgeons, de la floraison et de la formation des gousses. Au stress thermique s'ajoutait un faible (90 % d'eau disponible) ou fort (50 % d'eau disponible ) stress hydrique. En moyenne, un stress thermique de 3...

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SummaryBrassica juncea plants transformed with the Arabidopsis ADS1 gene, which encodes a plant homologue of the mammalian and yeast acyl-CoA ∆9 desaturases and the cyanobateria acyl-lipid ∆9 desaturase, were found to have a statistically significant decrease in the level of saturated fatty acids in seeds. The decrease in the level of saturated fatty acids is largely attributable to decreases in palmitic acid (16:0) The present study provides preliminary experimental data suggesting that the Arabidopsis ADS1 encodes a fatty acid ∆9 desaturase and could be useful in genetic engineering for modifying the level of saturated fatty acids in oilseed crops. However, the effect of ADS1 gene expression on seed oil fatty acid composition is beyond the changes of total saturated and mono-unsaturated fatty acids, which suggests a complex mechanism is involved in the regulation of fatty acid metabolism.

Canola-quality Brassica juncea is a potential alternative crop species in lower rainfall Australian environments due to its superior heat and drought tolerance, disease resistance, and pod-shatter resistance compared with the currently grown B. napus species. Canola-quality types of B. juncea that are adapted to flower and mature before water deficits and high temperatures significantly limit yield potential are currently being developed. In this study, the variability in phenological characteristics in canola-quality B. juncea is assessed, with a view to identifying the potential for including a range of genetic phenological controls on the development of the crop to assist with adaptation. Vernalisation response was compared among 17 lines of B. juncea and 3 of B. napus, using a cold treatment of 2.6°C for 25 days. Leaf number, and duration to first flower and maturity were compared in response to the vernalisation treatments. To assess day length response, the same 20 genotypes were sown at five locations with a range of sowing times, and one controlled environment, where day length was artificially extended. Development stages were assessed and the duration of particular phenological phases determined in relation to time, thermal time, and photoperiod. The major factor controlling flowering in canola-quality B. juncea genotypes was day length, with only small responses to vernalisation detected. There was sufficient variability in these traits and in thermal time to flowering under long days (intrinsic earliness) within the current canola-quality germplasm in Australia to select early flowering genotypes with potential adaptation to low-rainfall environments.

. 1997. Inoculation of seeds with Bipolaris sorokiniana and soil fumigation methods to determine wheat and barley tolerance and yield losses caused by common root rot. Can. J. Plant Sci. 77: 691-698. Wheat and barley plants that are severely infected with common root rot yield less than uninfected ones. Resistant cultivars usually have fewer diseased plants but some cultivars show tolerance as no yield loss occurs even though many plants display disease symptoms. This study assessed disease severity and yield loss due to common root rot in cultivars of wheat and barley by two techniques: i) sowing infested seed in soils with low inoculum levels of Bipolaris sorokiniana (Sacc. in Sorok.) Shoem., and ii) planting healthy seed in soil treated with the fumigants, metam and basamid. Infested seed exhibited reduced emergence, increased disease severity, but plot yield was not significantly affected compared with uninfested seed. The average yield loss or gain from seed treatment amongst all selections of wheat and barley was not significantly different. Losses were of the same magnitude (11.1% in barley, 6.2% in wheat) as reported in other studies. Soil fumigation reduced levels of B. sorokiniana in soil and disease severity. It also led to increased nutrient levels in soil and plant tissues, plant height, and plot yields by 16-29% compared with untreated areas. Tolerance to common root rot was exhibited by BW632, Virden, and Melvin. These losses are higher than reported in other studies which suggests yield loss may be underestimated or that common root rot is only one component of a root problem complex being affected by fumigants. infectées par l'agent de la pourriture sèche (piétin commun) rendent moins que les plantes saines. Les cultivars résistants produisent habituellement moins de plantes malades, mais il y a des cultivars dont la tolérance est telle que le rendement n'en souffre pas même si beaucoup de plantes portent les symptômes de la maladie. Deux techniques sont utilisées pour évaluer la gravité de la maladie et le manque à produire : i) semis des graines artificiellement infectées dans des sols faiblement contaminés par Bipolaris sorokiniana (Sacc. in Sorok.) Shem., et ii) semis de grains sains dans un sol traité au fumigant métame et basamide. L'infection artificielle abaissait le pourcentage de levée des plantules et accroissait la gravité des maladies, mais le rendement en parcelles ne s'en ressentait pas significativement par rapport à l'utilisation de grains sains . Les pertes ou les gains moyens de rendement attribuables à l'inoculation, toutes espèces et obtentions confondues ne différaient pas significativement. Les manques à produire étaient du même ordre de grandeur que ceux rapportés par d'autres chercheurs soit 11,1 % chez l'orge, 6,2 % chez le blé. La fumigation réduisait le taux d'infection du sol B. sorokiniana ainsi que la gravité de la maladie. Elle se causait également une amélioration de l'état nutritionnel des sols et des tissus végétaux. Les plantes étaient plus hautes et le rendem...