Broadening the avenue of intersubgenomic heterosis in oilseed Brassica

Abstract

Accumulated evidence has shown that each of the three basic Brassica genomes (A, B and C) has undergone profound changes in different species, and has led to the concept of the "subgenome". Significant intersubgenomic heterosis was observed in hybrids between traditional Brassica napus and first generation lines of new type B. napus. The latter were produced by the partial introgression of subgenomic components from different species into B. napus. To increase the proportion of exotic subgenomic components and thus achieve stronger heterosis, lines of first generation new type B. napus were intercrossed with each other, and subjected to intensive marker-assisted selection to develop the second generation of new type B. napus. The second generation showed better agronomic traits and a higher proportion of introgression of subgenomic components than did the first generation. Compared with the commercial hybrid and the hybrids produced with the first generation new type B. napus, the novel hybrids showed stronger heterosis for seed yield during the 2 years of field trials. The extent of heterosis showed a significant positive correlation with the introgressed subgenomic components in the parental new type B. napus. To increase the content of the exotic subgenomic components further and to allow sustainable breeding of novel lines of new type B. napus, we initiated the development of a gene pool for new type B. napus that contained a substantial amount of genetic variation in the A(r) and C(c) genome. We discuss new approaches to broaden the avenue of intersubgenomic heterosis in oilseed Brassica.

Patterns of Heterosis in Three Distinct Inbred Populations of Spring Brassica napus Canola

“…Several studies have demonstrated the value of utilizing allelic diversity of the allied Brassica species for increased heterosis in B. napus (Qian et al, 2005;Li et al, 2006;Zou et al, 2010;Girke et al, 2011Girke et al, , 2012Jesske et al, 2013;Li et al, 2014). For example, Zou et al (2010) observed a high level of heterosis in test hybrids while using germplasm diversified with the A genome of B. rapa and the C genome of B. carinata.…”

“…Several studies have demonstrated the value of utilizing allelic diversity of the allied Brassica species for increased heterosis in B. napus (Qian et al, 2005;Li et al, 2006;Zou et al, 2010;Girke et al, 2011Girke et al, , 2012Jesske et al, 2013;Li et al, 2014). For example, Zou et al (2010) observed a high level of heterosis in test hybrids while using germplasm diversified with the A genome of B. rapa and the C genome of B. carinata. A number of researchers have also utilized genetic diversity of resynthesized B. napus (from B. rapa × B. oleracea interspecific cross) for the improvement of openpollinated or hybrid winter B. napus cultivars (Gehringer et al, 2007;Radoev et al, 2008;Girke et al, 2011Girke et al, , 2012Jesske et al, 2013).…”

“…Thus, most of the studies conducted to date to evaluate different gene pools of Brassica for the improvement of spring or winter or semi-winter B. napus were focused on either the use of spring B. napus for spring type hybrid (Grant and Beversdorf, 1985;Brandle and McVetty, 1990;Engqvist and Becker, 1991;Diers et al, 1996;Cuthbert et al, 2009), or the use of winter or semi-winter B. napus for spring type hybrid (Butruille et al, 1999;Udall et al, 2004;Quijada et al, 2004Quijada et al, , 2006Qian et al, 2007;Kramer et al, 2009), or the use of winter or semi-winter B. napus for winter type hybrid (Lefort-Buson et al, 1987;Qian et al, 2009), or the use of the allied species for winter or semiwinter (Gehringer et al, 2007;Radoev et al, 2008;Zou et al, 2010;Fu et al, 2012;Girke et al, 2012;Li et al, 2014) or spring Seyis et al, 2006) type of hybrid. However, so far, no study has been conducted to compare the value of different gene pools for increasing the level of heterosis and seed yield in spring B. napus hybrid canola.…”

Characterization of interploid hybrids from crosses between Brassica juncea and B. oleracea and the production of yellow-seeded B. napus

“…The newly derived B. napus line may become a source of germplasm for broadening the genetic base and expanding yellow seed resources for B. napus. Importantly, by taking advantage of hybrids between the newly derived line and natural B. napus, stronger intersubgenomic heteroses between the subgenomic A j and A n , A r and A n , and C o and C n components could be studied and utilized (Zou et al 2010). From a breeding viewpoint, it is imperative that the reproductive efficiency and combining ability of the new B. napus lines, including those studied here, be properly evaluated in field trials before being used for heterosis.…”

Heterosis and Interspecific Hybridization

“…Inter-subgenomic heterosis may also occur in the disomic polyploid oilseed rape after partial introgression of subgenomic components from its different species (Zou et al 2010). Intensive DNA marker-aided selection in offspring ensuing from intercrossing first generation lines may assist increasing the exotic subgenomic components in further generations.…”