Making blue lupins more competitive

Background and Objective

In Spring 2015, the project "LupiBreed" started with the aim of improving the productivity of the blue and yellow lupin in terms of grain yield, yield security and stability as well as the quality of their nutritional components. Furthermore, the narrow genetic base of these crops is expanded by the inclusion of plant genetic resources to increase their potential for further breeding processing. "LupiBreed" is a joint project of Saatzucht Steinach, the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), the Thünen Institute of Organic Farming and the Julius Kühn Institute (project coordination).

In another work package, at the Thünen Institute of Organic Farming in Trenthorst we are researching preventative options for weed control and for optimizing mixed cropping. For this we record and evaluate the competitive ability of varieties and new breeding lines against weeds and mixed partners in intercrops. The aim of our investigation is to select particular characteristics such as a good plant development, leaf morphology and growth type during the breeding process more intensively in order to strengthen the preventive plant protection and the cost of weed control can be reduced.

Approach

In triannual plot trials we examine the competitive ability of lupins by seeding them with different partners in different seed rates. Hereby different competition situations are created, so that we can derive both the weed-suppressing effect as well as the suitability for mixed cropping.

In the first project year 2015, we cultivated the two varieties of blue lupine, Boruta (derminated type) and Boregine (branched type), in a plot trial at the site Trenthorst in a three-factorial block design with three field repetitions. As partner or artificial weeds, the monocotyledonous species wheat and oats, and the dicotyledonous species Camelina and a mixture with "artificial weeds" consisting of equal parts of rape, phacelia and buckwheat were used. In addition, we sowed the four partners in four seed densities to create as many different competitive situations as possible. As control, pure stands of the two blue lupin varieties, which were kept free of weeds, were cultivated, so that a competition against weeds was excluded.

In the second and third experimental year we will test the most promising variants and seed densities of the partners, resp. “artificial weeds”, in the test system for eight selected pre-breeding lines, while the two reference varieties will be tested further.

We sample the trial plots at different growth stages (shoot development, flowering, harvest) of the blue lupines. So we harvest the aboveground biomass, which are quantified separately for lupins, partners and weeds by square meter sections. In addition, we carry out an expert assessment of the plant development for coverage and plant height as well as measurements for Photosynthetically Active Radiation (PAR).

Results

In the project, a test system for the identification of prebreeding lines (PBL) of blue lupin (Lupinus angustifolius), developed in a mutagenesis program at the Julius Kühn Institute, was established. Hereby PBL could be identified with a good competitive power against weeds, which at the same time have a high yield in pure seed and in mixed cropping systems, as well as variants for an optimized intercropping system with blue lupins.

The test system was developed with the partner crops spring wheat, oat and false flax as well as so-called "artificial weeds", consisting of a mixture of winter rape, buckwheat and phacelia, which were grown in 4 different seed densities as additive mixtures with two varieties of blue lupins Boregine (branched) and Boruta (terminated). The evaluation of eight selected PBLs took place in 2016 and 2017 with two partner seed densities. The performance of PBL was considered on the one hand in comparison to the reference varieties and on the other hand depending on the growth types. To illustrate the competitiveness of the lupins, different levels of weed pressure were simulated. Suitability of blue lupin for mixed cropping was tested in additive mixtures at two reduced partner seed densities, while blue lupin was sown at 100 % sole cropping seed density.

Variety-specific differences in weed tolerance, which were also dependent on weed pressure at harvest time, were demonstrated. The varieties or PBL showed differences in weed suppression potential only at harvest.

A general advantage of PBL in its competitive power compared to the reference varieties could be found neither in pure seed nor in mixed cropping.

There were positive yield effects of intercropped blue lupins. A higher seed density of the partners resulted in better weed suppression, but without affecting the yields. In addition, PBLs with a good suitability for mixed cropping systems were identified.