Transfer of powdery mildew resistance from Brassica carinata to Brassica oleracea through embryo rescue

Abstract

Interspecific hybrid plants and backcross 1 (BC 1 ) progeny were produced through sexual crosses and embryo rescue between Brassica carinata accession PI 360883 and B. oleracea cvs ÔTitleistÕ and ÔCecileÕ to transfer resistance to powdery mildew to B. oleracea. Four interspecific hybrids were obtained through application of embryo rescue from crosses with B. carinata as the maternal parent, and their interspecific nature confirmed through plant morphology and random amplified polymorphic DNA (RAPD) analysis. Twenty-one BC 1 plants were obtained through sexual crosses and embryo rescue although embryo rescue was not necessary to produce first backcross generation plants between interspecific hybrids and B. oleracea. All interspecific hybrids and eight of the BC 1 plants were resistant to powdery mildew.Powdery mildew is a fungal disease of Brassica species caused by Erysiphe polygoni D.C. Erysiphe polygoni is an obligate pathogen and requires host tissue to grow and reproduce. Conidiospores are dispersed by wind or other means on to leaves where they germinate and penetrate host tissues. The pathogen reduces the vigour of host plants and sometimes causes significant yield losses and reduction in product quality. Powdery mildew is more common when weather conditions are cool and dry during late fall (Walker and Williams 1965). Brussel's sprouts and late maturing storage cabbages are infected by E. polygoni under field conditions. The disease is problematic during seed increases of Brassica species in greenhouses. Powdery mildew can be controlled by application of fungicides; however, fungicide application is often not desirable because of cost and environmental effects. Host plant resistance can be exploited as an alternative approach to controlling the disease. Some B. oleracea cultivars and accessions have moderate tolerance to the fungus (Walker and Williams 1965). However, many B. oleracea cultivars and accessions are highly susceptible to the disease. Resistant cabbage germplasm has previously been identified in which resistance was controlled by a single dominant gene with modifiers Williams 1965, Williams et al. 1968). Resistance also has been identified in related Brassica species, such as B. carinata and B. napus (Bradshaw et al. 1989, Singh et al. 1997.Interspecific hybrids can be produced between different Brassica species with the help of embryo rescue techniques, and provide potential for incorporation of different traits and for broadening the genetic base of cultivated Brassica crops (Prakash et al. 1999). Brassica carinata accession PI 360883 was identified as being resistant to powdery mildew in the greenhouse screening conditions (M. Tonguc¸and P. D. Griffiths, personal communication). The aim of the present study was to transfer powdery mildew resistance from B. carinata PI 360883 to B. oleracea to produce powdery mildew-resistant interspecific hybrids and backcross plants, and to enhance B. oleracea germplasm through incorporation of B. carinata chromosomal segments. Plant materials: Brassica c...

Biotechnology approaches to overcome biotic and abiotic stress constraints in legumes

“…Stress responses have not been assessed in these hybrids. However, the potential of this technique has been demonstrated in non-legumes crops where successful breeding for stress tolerance has been reported (Bradshaw et al, 1997;Tonguc & Griffiths, 2004). Protoplast fusion also has potential applications for crop improvement by overcoming sexual incompatibility or reproductive barriers, and by generating novel combinations of nuclear and/or cytoplasmic genomes (Liu et al, 2005).…”

Trigenomic Bridges forBrassicaImprovement

“…Genetic diversity may be further limited by geographical isolation, such as the "closed population" breeding of canola-quality B. napus in Australia from 1970 to 2000 (Cowling, 2007). However, valuable genetic variation exists in various A, B, and C subgenomes among the Brassica species of U's triangle, including genes for defense mechanisms against pests (Ahuja et al, 2010) and diseases (Roy, 1984;Zhu et al, 1993;Chèvre et al, 1997a;Westman et al, 1999;Saal et al, 2004;Tonguç and Griffiths, 2004;Saal and Struss, 2005;Chèvre et al, 2008). B. juncea and B. carinata have genes that enhance their heat and drought tolerance, such as those conferring better osmotic adjustment leading to greater water use efficiency, greater radiation efficiency (Gunasekera et al, 2009) and deep rooting (Malik, 1990).…”

Transfer of auxinic herbicide resistance from Brassica kaber to Brassica juncea and Brassica rapa through embryo rescue

“…Resistance to blackleg infection caused by Leptosphaeria maculans was transferred from B. kaber to B. napus (Snowdon et al 2000). Similarly, powdery mildew resistance was transferred from B. oleracea to Brassica carinata (Tonguc and Griffiths 2004). Nonetheless, trait transfer among Brassica members is not always straightforward, due to variations in chromosome number as well as ploidy among species (Mizushima 1950, 1980).…”

“…Nonetheless, trait transfer among Brassica members is not always straightforward, due to variations in chromosome number as well as ploidy among species (Mizushima 1950, 1980). Therefore, in vitro techniques such as ovule/embryo rescue is commonly employed to successfully produce interspecific hybrids among Brassica members (Inomata 1988; Mathias 1991; Bing et al 1995; Momotaz et al 1998; Tonguc and Griffiths 2004). …”