Veronique Troch

Biotic stresses in the anthropogenic hybrid triticale (×Triticosecale Wittmack): current knowledge and breeding challenges

Triticale (×Triticosecale Wittmack) is the intergeneric hybrid derived by crossing wheat (Triticum spp.) and rye (Secale spp.). Consequently, the same spectrum of fungal diseases occurring on the parent crops can impede optimal triticale production. With the expansion of the triticale growing area, the scientific interest into these fungal pathogens has gained momentum. This review considers the major fungal diseases occurring on triticale: powdery mildew, rust diseases, and Fusarium head blight and highlights breeding strategies or opportunities to control these pathogens. Although there are several models to explain the emergence of pathogens in newly introduced crops, for powdery mildew on triticale, it is accepted that it emerged through a host range expansion of wheat powdery mildew. Moreover, this host range expansion of wheat powdery mildew occurred recently, multiple times and at different locations in Europe. For rust diseases and Fusarium, evidence for such an abrupt host shift is rather thin and suggests an evolution in disease incidence and virulence confluent with evolving management practices, variable seasons, mutations, recombination and variety selection. In order to overcome these fungal pathogens in triticale, plant breeding is a powerful tool. Despite the multiple parallelisms between fungal diseases in triticale and wheat, the narrow genetic background, partially due to the narrow genetic background of the parental crops, is a serious issue in triticale breeding. It remains a challenge for future breeding strategies to broaden the genetic background of new varieties that are being developed, through introgression and deployment of new sources of disease resistance. Especially, quantitative and multi-pathogen sources of resistance have to be considered. In this way, triticale can retain its position as important low input farming cereal crop.

Development, maturation and germination of horse chestnut somatic embryos.

Somatic embryogenesis could represent a way to clonally propagate mature elite trees of horse chestnut. However, while a number of protocols describe successfully the induction and proliferation of somatic embryos a low frequency of embryos converted successfully into plants. The objective of this research was to identify a maturation medium that could contribute to the outcome of more efficient germination results. Therefore, in a first approach the effects of sucrose 3 and 6%, and maltose 3%, were evaluated on somatic embryo maturation, in terms of subsequent somatic embryo germination. Carbon source and concentration had a marked influence on maturation, and subsequent germination of horse chestnut somatic embryos, with sucrose 6% promoting the highest frequency of germinated embryos larger than 1 cm.