Rapid-cycling populations of six economically important species in the genus Brassica have unusual potential for resolving many problems in plant biology and for use in education. Rapid-cycling brassicas can produce up to ten generations of seed per year and serve as models for research in genetics, host-parasite relations, molecular biology, cell biology, plant biochemistry, population biology, and plant breeding. Brassicas are a highly diverse group of crop plants that have great economic value as vegetables and as sources of condiment mustard, edible and industrial oil, animal fodder, and green manure. These plants can also be used in the classroom as convenient, rapidly responding, living plant materials for "hands on" learning at all levels of our educational system.

https://science.sciencemag.org/content/sci/232/4756/1385.full.pdf

Rapid-cycling populations of Brassica

Doubled Haploid Production in Crop Plants

Somatic embryogenesis is the formation of an embryo from a cell other than a gamete or the product of gametic fusion This is not an artificial phenomenon, and is known in nature as a form of apomixis called adventitious embryony, first described by Strasburger in 1878 [1] (see Sharma and Thorpe, this volume) Although Steward [2] and Reinert [3] are generally given credit for the first descriptions of somatic embryogenesis in 1958, such credit might more properly belong to Levine [4], who in 1947 reported the recovery of carrot “seedlings” from tissues exposed to low levels of α-naphthaleneacetic acid, via a process whose description sounds very much like somatic embryogenesis

Morphogenic Aspects of Somatic Embryogenesis

High frequency embryogenesis through isolated microspore culture in Brassica napus L. and B. Carinata braun

Microspore embryogenesis is the most commonly used method to produce doubled haploids. It is based on the ability of a single haploid cell, the microspore, to de-differentiate and regenerate into a whole plant after being exposed to stresses, such as low or high temperatures, carbon starvation and colchicine. Some stresses such as temperature treatments and carbon starvation have been used with success in many plant species, whereas others such as colchicine had limited application in a few species. Reports on the application of whole plant treatments with feminizing agents on inflorescences and buds are scarce. Furthermore, the technical means to apply some stresses such as γ-irradiation are not readily available. Recently, novel stresses such as pH, inducer chemicals, carrageenan oligosaccharides and heavy metals were reported to induce microspore embryogenesis. It remains to be seen, however, whether these stresses are effective in a wider range of species. Finally, pretreatment of cultured cells with high concentrations of 2,4-D efficiently induces somatic embryogenesis in several species (carrot, alfalfa). However, reports on the use of this particular chemical stress are not available in microspore embryogenesis. The paper presented here gives an overview of various stresses and mechanisms of action of these stresses in inducing microspore embryogenesis.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1399-3054.2006.00675.x

Stresses applied for the re‐programming of plant microspores towards in vitro embryogenesis

SUMMARY

Following anther culture of a range of cultivars of winter oilseed rape, Brassica napus ssp. oleifera, approximately 15 to 70 % of the resulting embryoids developed directly into plants. The rest grew abnormally in culture, giving rise to abnormal plantlets which formed large numbers of secondary embryoids on their surfaces (up to 100 per abnormal plantlet). The secondary embryogenic plantlets were haploid, and the secondary embryogenic potential was maintained for over a year in culture without diminution. More than 70% of the secondary embryoids, and the plants regenerated from them, were haploid. These results are discussed in connection with the possibility of producing large numbers of haploid plants throughout the year for breeding purposes and for the production of novel disease resistant plants through genetic manipulation in culture.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.1982.tb03329.x

Production of haploid plants from anther cultures and secondary embryoids of winter oilseed rape, brassica napus ssp. oleifera

It was shown that only a small proportion of haploid (= amphihaploid; n = 19) secondary embryoids of winter oilseed rape (Brassica napus ssp. oleifera) grew into plants when transferred to a medium without plant growth regulators. The majority grew abnormally and formed further secondary embryoids on their surfaces. It was then found by experiment that an effective method of inducing leaf initiation and reducing secondary embryogenesis was to transfer the secondary embryoids to a basal medium supplemented with 6-furfurylaminopurine (kinetin; 10-4 M), alone or in combination with low concentrations of indole-3-acetic acid. Roots were initiated by further transfer of the cultures to basal medium without plant growth regulators. The plantlets so produced were normally haploid and were suitable for growing on into whole plants. The reduction of secondary embryogenesis by cytokinins is discussed in the general context of response by plant tissues to plant growth substances.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.1983.tb03502.x

Cytokinins and the regeneration of plantlets from secondary embryoids of winter oilseed rape, brassic a nap us ssp. oleifera

SUMMARY
Culture filtrates of Alternaria brassicicola (Schw.) Wilts, were found to be toxic to secondary embryoids of Brassica napus ssp. oleifera (Metzg.) Sinsk. The culture filtrates were partially purified and added to tissue culture media to produce a selection medium. Different secondary embryoid lines of B. napus were found to differ in their sensitivity to the selection medium, and it was possible to select lines which showed increased resistance to the selection medium. Some plants that were regenerated from secondary embryoids were found to be more resistant to the pathogen than were seed-grown plants of the same cultivar, although there was no correlation between sensitivity to the selection medium and susceptibility to the pathogen.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.1986.tb00662.x

Towards the selection in vitro for resistance to Alternaria brassicicola (Schw.) Wilts., in Brassica napus ssp. Oleifera (Metzg.) Sinsk., winter oilseed rape

SUMMARY
It was shown by experiment that the treatment of cultured haploid detached secondary embryoids and secondary embryogenic tissues of Brassica napus ssp. oleifera with colchicine resulted in diploidy, tetraploidy and mixaploidy. The proportions of the different ploidy levels so induced depended on the concentration of colchicine used and the duration of treatment. The highest levels of diploidization were obtained by exposing the tissues to 0.05 % colchicine in 2% dimethylsulphoxide for 72 h. The capacity for secondary embryogenesis was retained in colchicine-induced diploid, tetraploid and mixaploid tissues, and the majority of the resulting second generation secondary embryoids were of the same ploidy as the parental material. This indicates the stability of the secondary embryogenic potential irrespective of changes in ploidy level. It is suggested that the ability to produce secondary embryoids is a consequence of haploidy and homozygosity. That the phenomenon is not a consequence of growth in culture is indicated by the fact that secondary embryoids are also produced occasionally on mature glasshouse-grown plants regenerated from secondary embryoids. It is concluded that a system is now available for the continuous production of large numbers of haploid and homozygous diploid plants, and plants of other ploidy types, all derived from the same haploid anther embryoid. Such a system will be of value for oilseed rape breeding and for genetical and biochemical studies of somatic embryogenesis.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.1983.tb03503.x

D. S. Ingram

Papers

Production of haploid plants from anther cultures and secondary embryoids of winter oilseed rape, brassica napus ssp. oleifera

Cytokinins and the regeneration of plantlets from secondary embryoids of winter oilseed rape, brassic a nap us ssp. oleifera

Towards the selection in vitro for resistance to Alternaria brassicicola (Schw.) Wilts., in Brassica napus ssp. Oleifera (Metzg.) Sinsk., winter oilseed rape

The response of haploid secondary embryoids and secondary embryogenic tissues of winter oilseed rape to treatment with colchicine

Rapid-cycling Brassica Species: Inbreeding and Selection of B. campestris for Anther Culture Ability