Lupins are recognised as a valuable source of protein in livestock diets. Previous attempts to produce lupins in the UK were not successful. UK production was seen as important for reasons of import substitution (of soya), traceability and GM crop contamination. Research was conducted for more than 10 years to understand and overcome the limitations to lupin production in the UK. Much was funded by DEFRA (formerly MAFF), BBSRC (formerly AFRC) and the EU also contributed significant resources.
Most of the work focussed on Lupinus albus
(white lupin) and specifically autumn sown cultivars as these were seen to offer the greatest potential to UK agriculture. In 1998 it was recognised that other species, (L. angustifolius
and L. luteus
) also had a valuable role to play in the UK lupin industry. Only small scale industrial funds were available to investigate these exclusively spring sown possibilities
A major breakthrough in the cultivation of all lupin species in the UK was the identification of the suitability of genetically more determinate cultivars. The growth of the lupin plant is modular. Modules consist of individual stems producing leaves and ending with a terminal inflorescence. Further modules, belonging to the next (branch) order, may emanate from the leaf axils of the previous order. Cultivars in which the number of orders of modules to grow is under genetic control are more reliable in the mild damp summer conditions of the UK. Such cultivars matured more reliably than those relying on an environmental trigger to bring an end to such vegetative growth.
Autumn sowing allowed early flowering after the production of numerous leaves compared to spring sowing. This gave a longer period of good growing conditions for seed yield to be set whilst maintaining an acceptable maturity / harvest date.
Studies of over-winter survival of autumn sown cultivars greatly enhanced our knowledge of cold tolerance in L. albus
. Within the autumn sown cultivars and the progenitors it was not possible to determine clear genetic variation for cold tolerance. Clear identification of the role of the environment on plant development allowed definition of the most cold tolerant phases in plant development. The models developed from this work were used with historical meteorological records to define management packages or agronomy that maximised the over-winter survival of the crop.
The over-winter survival data and models contributed to the determination of the recommended seed rate. Initial estimates of optimal spring and summer plant densities were purely empirical. Later it was realised that the plant density was a vital factor controlling seed yield variation. More specifically the greater proportion of the incident light reaching the lowest pods in the canopy the greater the seed yield attained (all other things being equal). Canopy architecture and light penetration were controlled by plant density and the number of branches or modules in the first order component.
Studies of the effects of the environment on plant architecture (number of modules in each branch order) led to the development of models for these processes. The interaction of plant architecture with plant density (canopy architecture) was more empirical. These models were used in combination with the over-winter survival model and historical meteorological records to generate site specific management recommendations
, particularly sowing windows.
produces a large pod wall (thick with a large dry weight), larger than most other grain legumes. This was seen as a waste of resources as it was dry matter that was not harvested as economic yield (a detrimental affect on harvest index). Selecting for genotypes with smaller pod walls (lower dry weight and thickness) appeared to have a generally positive affect on seed yield. In addition the pod wall of L.albus
is known to be a photosynthetic organ. In our experimentation much of that photosynthetic activity was internal re-fixation of respiratory CO2
. Net gas exchange with the environment was low compared to other photosynthetically active organs. It was hypothesised that smaller pod walls would increase net gas exchange to the benefit of seed yield. Comparison of two genotypes showing similar growth except for the size of the pod wall only demonstrated the large variance encountered in making replicate measurements of net gas exchange by such organs.
Wide-scale testing of the first autumn sown determinate cultivars showed that the time of maturity was not as reliable as at first thought. Studies revealed that the availability of soil water was the dominant factor controlling the rate of maturation in late summer and that air temperature and to a lesser extent humidity also had an influence. The smaller pod wall character (and hence potentially greater rates of water loss) showed no benefit in terms of earlier maturity times.
A number of fungal diseases are known to infect cultivated lupins. Most proved relatively easy to control. Pleiochaeta setosa
has not been common in UK crops despite being a serious disease of lupins elsewhere in the world. The seedling disease caused by the pathogen has not been recorded in the UK and later in the life of the plant infection of stem and pod is easily controlled by the same fungicides that control rust (see below). Genetic resistance to Fusarium
spp. has proved sufficient for most situations where the plant has not been previously physically damaged. Botrytis cinerea
was much less common following the recommendation that crops be grown with more open canopies to improve light penetration to depth. Rust (Uromyces lupinocolus
) is probably the most common fungal pathogen of L. albus
, autumn sown crops require 2 fungicide sprays on most sites and in most seasons. Fortunately the rust is susceptible to low rates of low cost fungicides.
Anthracnose is a potentially devastating fungal disease of all cultivated lupins. It does not survive well in the environment. In any one year background infection from the environment is unlikely to harm a crop seriously. However, if seed is re-sown from such a crop, even with low levels of infection, and weather conditions are suitable the effect on the second crop can be devastating (total crop loss is a possibility). Fungicidal control proved costly and a little unreliable. Therefore the responsibility lies with the seed producers to ensure through attention to crop monitoring and general hygiene that seed is free of infection. Conventional seed testing techniques proved inadequate to detect the very low levels of infection considered capable of causing crop loss (1 infected seed in 10,000).
Rothamsted Research made a collection of genotypes of the causal fungus (Colletotrichum acutatum or C. gleosporoides) and tested them for pathogenicity on L. albus cv. Lucille (a commonly grown cv.). There was some debate about the taxonomy of the genotypes within the two species and conventional (fungicide sensitivity) and molecular (primer sequences) were used to distinguish the species. rDNA from the genotypes was treated with four enzymes in the search for a banding pattern common to pathogenic genotypes that could be used as the basis of a molecular test sensitive enough to detect infection at the 1 in 10,000 level. It was not possible to develop this work further in the timescale of the projects.
All cultivated lupins are sensitive to alkaline soils which restricts the extent of cultivation in the UK. The soil pH limits (4.8 to 7.2) of cultivation were defined in order to inform the industry. L. albus showed the greatest genetic variation for tolerance to such soils. The bio-chemical and physiological basis for intolerance to alkaline soils were defined as; an inability to maintain the concentration of iron II (Fe II) in the sap when faced with large quantities of bicarbonate flowing into the plant from the soil (most Fe being Fe III under such circumstances) and an inability to control the quantity of soluble Ca in the leaf.
Genotypes of L. albus more tolerant of alkaline soils and displaying indicators of possible mechanisms to control Fe II and soluble Ca were identified. These were used to develop non-destructive repeatable screens for tolerance to be used in the breeding of tolerant cultivars.
The effect of the environment on the tolerance of a genotype to an alkaline soil was investigated. It was hypothesised that the partial pressure of CO2 in the soil influenced the quantity of bicarbonate entering the plant and therefore the potential for the plant to maintain internal Fe II concentrations. The partial pressure of CO2 in the soil is controlled by soil aeration which in turn is controlled by soil texture, structural condition and water status. The potential soil bicarbonate concentration is primarily a function of the soil carbonate content, modified by the partial pressure of CO2.
The project aimed to quantify these factors with respect to the intensity of stress experienced by a standard L. albus genotype. This would allow a more sophisticated prediction of land suitability for L. albus production and would be useful in defining the test conditions when screening breeding material.
A considerable effort was put into Knowledge Transfer alongside the commercial introduction of the first autumn sown L. albus
cultivars. Commercial introduction struggled due to the over dependence on the sowing window (despite an in depth understanding of the processes and detailed guidance) and an industry perception that the crop required a large number of inputs (herbicides and fungicides). Both factors are to be considered in comparison with many spring sown cultivars of lupin which are easy to grow and produce similar yields to the autumn sown cultivars.