The inheritance of erucic acid content in Ethiopian mustard

Ethiopian mustard (Brassica carinata A. Braun) is a highly productive oilseed crop in the central highlands of Ethiopia. Cultivars currently in production in Ethiopia produce seed which contains 35–40% erucic acid in its oil which is undesirable for human consumption. Zero erucic acid B. carinata has recently been developed. The objective of this study was to investigate the inheritance of erucic acid in progeny of crosses between the high erucic acid cultivars Dodolla and S-67 with the zero erucic acid line C90-14. The erucic acid content of F1 seed born on either the high or low erucic acid parents was intermediate between the parents indicating embryonic control of erucic acid content in B. carinata. Erucic acid contents of backcross seed derived from the backcross to the zero erucic acid parent segregated into three classes with <0.5%, 6–16% and >16% erucic acid at a ratio of 1:2:1 and F2 seed segregated into five classes with a ratio of 1:4:6:4:1. These segregation patterns indicated that erucic acid in B. carinata was controlled by two genes acting in an additive manner with each locus contributing about 10% erucic acid. It was concluded that the B and C genomes of B. carinata each carry one gene for erucic acid synthesis. The knowledge of the inheritance of erucic acid in B. carinata will assist in the development of zero erucic acid B. carinata cultivars. Key words:Brassica carinata, erucic acid, inheritance

Physical and chemical defences of pods and seeds of white mustard (Sinapis alba L.) against tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois) (Heteroptera: Miridae)

Adult tarnished plant bugs (Lygus lineolaris) fed 5–10 times less frequently on seeds within pods of white mustard (Sinapis alba L.) than on seeds within pods of canola (Barssica napus L.) in no-choice feeding tests in the laboratory. The presence of long, sharp spines (trichomes) on pods of S. alba did not account for all of the difference in feeding on this mustard and on the smooth pods of canola because the feeding rate on shaved pods of S. alba was only twofold higher than on unshaved controls. Lygus lineolaris fed four times less frequently on seeds within pods of a commercial cultivar than on seeds of a near-isogenic low-glucosinolate line of S. alba, suggesting that it is the high concentration of the glucosinolate "sinalbin" in seeds that largely determines the low rate of feeding of L. lineolaris on this species.Plant breeders are currently developing low-glucosinolate lines of mustards such as S. alba for the oilseed market. Seed damage by L. lineolaris in an oilseed S. alba likely will be considerably higher than currently occurs in the mustard S. alba. Key words:Brassica, Sinapis, Lygus, trichome, glucosinolate, feeding damage, antixenosis

Inheritance of the waxless character of Brassica napus Nilla glossy

Inheritance studies using two reciprocal and two backcross combinations made from a wax-less (Wl) line of oilseed rape, B. napus 'Nilla glossy' and two normal wax (Nwl) genotypes showed that the Wl character of Nilla glossy is recessive to the Nwl. Chi-square tests revealed that the segregation ratios of B1 and F2 plants fit 3:1 and 15:1 (Nwl:Wl) ratios, respectively, and these are consistent with the presence of two gene pairs. Key words:Brassica napus, epicuticular wax, genetic marker, cer mutant

The possible role of embryo sac degeneration in yield reduction of summer turnip rape cultivar Candle

When pollination occurred within 24 h after anthesis, 69.2% of the pods of Brassica rapa cultivar Candle contained at least 50% fertilized ovules. If pollination occurred later than 4 d after anthesis, an occasional ovule near the base of the pistil was fertilized; however, no significant seed set was observed. Pollen tubes were observed entering the locules of the ovary from pollinations carried out as late as 5 d after anthesis. At 3 d after anthesis, in unpollinated flowers, a general deterioration of the embryo-sac contents began and gradually increased to include integumentary cells by 6 d after anthesis. Some ovules swelled as though they were fertilized, but no embryos were present. The results suggest that yield reductions in this species may occur because of the reduction of fertilization potential through rapid degeneration of embryo sacs following anthesis. Key words:Brassica rapa, embryo sac, yield

Free fatty acid levels in Ontario-grown summer rape cultivars

High levels of FFA have been a recurring problem in the seed oil of Ontario-grown, canola-quality summer rape (Brassica napus L.). Examination of seed samples from the Eastern Canadian Co-operative Cultivar Trials conducted at several locations in 1988–1993 showed significant, consistent differences in FFA levels among cultivars. In each year from 1988 to 1991 the cultivars Kristina, Delta and Westar had FFA levels that were about 40% of those of Global and the triazine-tolerant cultivars Stallion, OAC Triton and OAC Triumph. Pearson's correlations and Spearman's rank correlation between years for FFA levels of genotypes were all significant, with the exception of the Spearman's rank correlation between 1992 and 1993. Significant differences in FFA occurred among locations in southern Ontario, but location differences were not consistent across years. Cultivars grown in western Canada, however, had FFA levels between 2 and 41% of their FFA levels at the southern Ontario locations. The FFA levels of cultivars at one Ontario location were significantly correlated with the mean FFA levels of the same cultivars from all the other Ontario locations in the same year, 28 out of 34 times. Correlations were higher before the high-FFA cultivars were removed from the trials in 1991. Screening of lines in a breeding program for susceptibility to high FFA at one southern Ontario location appeared to be predictive of FFA levels at other southern Ontario locations. Selection of cultivars that have low FFA levels should reduce the FFA problem in Ontario-grown spring canola. Key words:Brassica napus, canola, free fatty acids, cultivars, stress, environment

Effects of time and rate of application of triazole fungicides on incidence and severity of blackleg and growth and yield of canola

The ability of three triazole fungicides to reduce blackleg and to increase the yield of spring canola (Brassica napus) was tested at four locations in Ontario in 1990 and 1991 in fields containing stubble infested with Leptosphaeria maculons. In test 1, triadimefon (3.46 kg ha−1), diconazole (1.41 kg ha−1) and uniconazole (2.12 kg ha−1) were sprayed on foliage at the late rosette stage, or when flowers were opening on the main raceme, or at both growth stages at half rate (split). Split applications were most effective and reduced disease incidence and severity by 9.2 and 22.6%. Yields were not increased. In test 2, the fungicides were applied at the late rosette stage at four rates. The highest rates of triadimefon (9.24 kg ha−1), diconazole (3.76 kg ha−1) and uniconazole (5.64 kg ha−1) reduced disease incidence by 12.8, 10.6 and 6.4%, reduced disease severity by 25.7, 31.8 and 24.2%, and increased yield by 17, 33 and 30%, respectively. In both tests, most treatments increased seed weight, delayed crop flowering and maturity, reduced lodging and height, and increased vigor. Triazole fungicides applied as foliar sprays can reduce blackleg and improve yield of canola. Key words:Brassica napus, canola, triadimefon, diconazole, uniconazole, blackleg

Development of zero erucic acid Ethiopian mustard through an interspecific cross with zero erucic acid Oriental mustard

Ethiopian mustard (Brassica carinata A. Braun) is a high-yielding oilseed crop of the Ethiopian highlands, but the seed is high in erucic acid. The objective of this study was to develop zero erucic acid forms in this mustard species. This was achieved through an interspecific transfer of genes for zero erucic acid from Brassica juncea. Key words:Brassica carinata, zero erucic acid

Growth stress induces glucosinolate changes in pakchoy (Brassica campestris ssp. chinensis)

Glucosinolates (GS) are sulphur-containing compounds that yield breakdown products that contribute to the characteristic flavor and aroma of Cruciferae crops. No studies have been conducted on the influence of the environment on the GS levels in the leafy vegetable pakchoy (Brassica campestris ssp. chinensis). Because of the importance of GS, we studied in two separate experiments, the effect of nitrogen (N) nutrition and turnip mosaic virus (TuMV) infection on the GS content of this vegetable. As part of our study in a separate experiment, we also determined the GS profile of developing plants from 5 to 35 d. Nitrogen was applied at 14, 84, and 224 mg L−1 and plants were manually inoculated with TuMV during early (15 d) and late (30 d) development. Plants were grown hydroponically and harvested 35 or 36 d after seeding. Developing plants accumulated GS in leaf tissues. Nine GS were detected in pakchoy tissues. Plants supplied with 14 mg L−1 N and those infected with TuMV during early development had lower fresh and dry weights and had higher total GS content than control plants. Alterations in the concentrations and relative percentages of several GS were also evident in these plants. A decline in the 1-methoxy-3-indolylmethyl-GS percentage in the mature leaf tissues of stressed plants commonly occurred. Data from these experiments indicated that certain GS changes in pakchoy were tissue and stress specific. Key words:Brassica, glucosinolates, nitrogen, turnip mosaic virus

Performance of inter-cultivar summer turnip rape hybrids in Saskatchewan

The agronomic performance of inter-cultivar hybrids of Brassica rapa L. was studied in crosses between four B. rapa cultivars. Six reciprocal hybrid combinations were produced by hand pollination in the greenhouse. Hybrids and their parents were tested in replicated yield tests for 3 yr. An average, over all hybrid combinations, of 13% heterosis for seed yield was observed. Heterosis for seed yield was greatest in crosses between genetically diverse cultivars, which agrees with classical theories on heterosis. There were also significant differences in yield of reciprocal F1 combinations. Seed oil content was not heterotic. The results of this study indicated that the level of heterosis of seed yield in crosses between B. rapa cultivars adapted for production in western Canada is sufficient to warrant the development of a suitable pollination control system for hybrid B. rapa production. Key words:Brassica rapa, Brassica campestris, inter-cultivar hybrids, seed yield, heterosis

Vernalization response in spring oilseed rape (Brassica napus L.) cultivars

Early maturity is a major objective of oilseed rape (Brassica napus L.) breeding programs in western Canada. Maturity of crops is influenced by time of initiation and flowering. The presence of a vernalization requirement affects plant development by delaying floral initiation until the cold requirement of the plant has been satisfied. Five spring oilseed rape cultivars were screened for their response to vernalization. Vernalization treatments consisted of exposure of germinated seeds to 0–42 d at 4 °C. Plants were assessed under a 20-h photoperiod. In general, there was a cumulative response to vernalization, with a decrease in days to each developmental stage as exposure to 4 °C was increased. Vernalization treatment of 6 d at 4 °C was sufficient to decrease both the days to first flower and the final leaf number. The characterization of vernalization response is of interest because variation in flowering time in response to year-to-year variations in the environment could result. Key words:Brassica napus, canola, oilseed rape, vernalization