Genetic and molecular characterization of breeding-relevant traits of narrow-leafed lupin (<em>Lupinus angustifolius</em> L.)

Abstract

Narrow-leafed lupin is considered to be a legume with great future potential because of its high and valuable protein content. Cultivated lupins appear in agricultural production in diverse forms and for very different purposes: grain production and forage in crop rotation, green manure, and as a relatively new area the production of healthy food products. Therefore, novel cultivars for these particular applications are needed. Successful breeding of varieties requires genetic variability with a broad spectrum of agronomic traits. But genetic variation of narrow-leafed lupin, a self-pollinator, is limited due to the bottleneck of former selection for sweetness.

These days overriding goals in lupin breeding are yield stability and yield increase.

Yield stability may be achieved by breeding for anthracnose resistance as it is the most severe disease in lupin cultivation worldwide. Therefore, a screening for anthracnose resistance of a set of plant genetic resources of NLL identified the breeding line Bo7212 as being highly resistant to anthracnose (C. lupini). Segregation analysis of experimental mapping populations indicated that the resistance of Bo7212 is inherited by one single dominant locus. Published molecular anchor markers as well as further sequence information obtained from the model genome Lotus japonicus, RNASeq data and genome sequence information of NLL allowed us (i) to locate the locus LanrBo on linkage group NLL-11 and (ii) to identify closely linked markers that allow for precise marker-assisted selection for LanrBo in narrow-leafed lupin breeding programs.

In an EMS-based mutagenesis program 40,000 seeds of cv. 'Boruta' were treated and a variety of phenotypic mutant lines expressing novel growth types with altered plant height and branching were obtained. These lines promise a potential yield increase. In field trials at two locations for three years, three of a subset of these lines exhibited significantly improved grain yield components compared to the wild type cv. 'Boruta', indicating a successful yield increase by indirect selection for novel branching behaviour. Growth types of these promising lines were shown to be inherited in a monogenic recessive manner and should, hence, be easily fixable in breeding programs.

To conclude, this work demonstrates (i) the successful exploitation of plant genetic resources regarding yield stability and (ii) the increase of genetic variability by chemical mutagenesis. This may result in anthracnose-resistant lines and high-yielding growth types. The combination of both factors in targeted breeding programs by using novel molecular selection tools is a promising and efficient basis for the development of powerful lupin varieties.