Oilseed crops of the Cruciferae are widely adapted and are of particular importance to countries in the northern latitudes. Cruciferous seed oils from the crops, rapeseed, mustard, Camelina, oilseed radish and Crambe, enter edible or industrial markets, or both. The oil-seed meal can be used either as a high protein feed supplement or as an organic fertilizer. The spring and winter forms of the two species of rapeseed,Brassica napus andB. campestris, are commercially the most important. Advances in crop management and plant breeding have resulted in a 40% to 50% increase in seed yield over the past 25 years. In the next 10 to 15 years, application of newer plant-breeding techniques will result in varieties even higher in yield and seed with improved oil and meal quality. Some of the quality improvements will be new patterns in fatty acid composition, higher oil and protein content, lower fiber content, and removal of the undesirable glucosinolate compounds from the meal. The mustard cropsBrassica juncea andB. hirta are important condiment crops which have considerable potential as edible oil sources. Oilseed radish,Raphanus sativus, yields significantly less seed and oil than other cruciferous oil crops but its oil, which contains a low level of erucic acid (3.7%) and a relatively high content of 16-carbon fatty acids (9.3%), may be useful in blending with normal or zero erucic acid rapeseed oils.Camelina sativa or false flax has many desirable agronomic characteristics but the oil of camelina seed contains too high a level of linolenic acid (36%) to penetrate the edible oil market and too low to compete industrially with linseed oil.Crambe abyssinica andC. hispanica are potentially important producers of high erucic acid industrial oils. Factors limiting Crambe development are the high cost of seed transportation due to the high volume to weight ratio of the threshed seed and the need for extra seed processing steps to render the meal suitable as a high protein feed supplement for livestock and poultry.

Agricultural and genetic potentials of cruciferous oilseed crops

Estimating quantitative contributions to specific traits can be accomplished from a variety of genetic models (Mather 1949; Mather and Jinks 1971; Falconer 1981). Residual genetic effects, those beyond main and interaction effects of the embryo genotype, are often pooled under a single classification, termed maternal effects. Maternal contributions to seed-related traits can originate from various maternal sources (e.g., endosperm, testa and cytoplasm). Quantitative contributions of a maternal nature are not predictable from parental performance and effects are largely non-persistent over generations (Jinks et al. 1972). The methods used to determine maternal effects in quantitative traits often do not measure quantitative genetic parameters, while those that do are either complex or partially resolve potential contributions of individual sources of maternal effects. We present simple genetic models for estimating quantitative genetic parameters which take into account maternal effects expressed in the major seed tissues of higher plants.

Models to estimate maternally controlled genetic variation in quantitative seed characters

Selections for different levels of C18 fatty acids in rapeseed to date have had only limited success, due in part to the low frequency of occurrence of desired genotypes with increased linoleic and decreased linolenic acid. In the progeny of mutation experiments with seeds of the variety Oro (linolenic acid content 8–10%) two stable mutants were selected, one with 5% and the other with 20% linolenic acid in the seed oil. The level of linoleic acid in the two mutants is the same as Oro (16–20%), but the levels of oleic and linolenic acids are inversely altered. In this paper several problems associated with selecting for linoleic and linolenic acids, which became apparent during the mutation studies, are discussed. Many selections made from the mutated material were unstable, reverting to the original Oro fatty acid composition after two or three self-pollinated generations. This fact plus environmental and maternal effects made selection difficult. However, with the use of rapid and simple analytical methods and space-saving growing techniques, these difficulties were overcome.

Opportunities and problems in modification of levels of rapeseed C18 unsaturated fatty acids.

The primary aim of this study was to optimize in vitro culture protocols to establish an efficient reproducible culture system for different Brassica interspecific crosses, and to synthesize yellow-seeded Brassica napus (AACC) for breeding and genetical studies. Reciprocal crosses were carried out between three B. rapa L. ssp. oleifera varieties (AA) and five accessions of B. oleracea var. acephala (CC). All the parental lines were yellow-seeded except one accession of B. oleracea. Hybrids were obtained through either ovary culture from crosses B. rapa × B. oleracea, or embryo culture from crosses B. oleracea × B. rapa. A higher rate of hybrid production was recorded when ovaries were cultured at 4–7 days after pollination (DAP). Of different culture media, medium E (MS with half strength macronutrients) showed good response for ovaries from all the crosses, the highest rate of hybrid production reaching 45% in B. rapa (1151) × B. oleracea (T2). In embryo culture, the hybrid rate was significantly enhanced at 16–18 DAP, up to 48.1% in B. oleracea (T3) × B. rapa (JB2). The combinations of optimal DAP for excision and media components increased recovery of hybrids for ovary and embryo culture, and constituted an improved technique for B. rapa × B. oleracea crosses. In addition, yellow seeds were obtained from progenies of two crosses, indicating the feasibility of developing yellow-seeded B. napus through the hybridization between yellow-seeded diploids B. rapa and B. oleracea var. acephala.

Improving ovary and embryo culture techniques for efficient resynthesis of Brassica napus from reciprocal crosses between yellow-seeded diploids B. rapa and B. oleracea

The oleic, linoleic, and linolenic acid content of rapeseed (Brassica napus L.) oil was investigated in self- and cross-pollinated seed on parental lines and reciprocal F1 populations. The seed was derived from three strains of rapeseed that produce seed oil practically free of eicosenoic and erucic acids. A definite maternal genotype effect on the oleic and linoleic acid content of the cross-pollinated embryo was evident in two of three combinations. Embryo control for the quantities of these two fatty acids was indicated for the third combination. Both embryo and maternal genotype control of linolenic acid content was indicated. There were no cytoplasmic effects evident in the reciprocal F1 populations for any fatty acid in all three combinations.

B. R. Stefansson

Papers

A maternal effect on the fatty acid composition of rapeseed oil (Brassica napus)