Ecogeography of the Old World lupins. 1. Ecotypic variation in yellow lupin (Lupinus luteus L.)

Abstract

Agricultural crops and their wild progenitors are excellent candidates for ecophysiologal research because germplasm collections are often extensive and well described, and in its dissemination the crop may explore new habitats. The advent of high-resolution climate models has greatly improved our capacity to characterise plant habitats, and study species’ adaptive responses. The yellow lupin (Lupinus luteus) is ideal because it evolved as a Mediterranean winter-annual in relatively high-rainfall coastal regions, but was domesticated as a summer crop in temperate central Europe. Currently the crop is being developed for Mediterranean south-western Australia, raising an interesting ecophysiological problem: is it more appropriate to concentrate on wild material from Mediterranean habitats, which are likely to be more similar to the target environments, or on European germplasm domesticated for temperate summer cropping? Lupinus luteus collection sites across the natural and domesticated distribution range were characterised by calculating site-specific bioclimatic variables and habitat types defined using multivariate analysis. Germplasm was evaluated in 2 field trials measuring a range of characters describing plant growth, phenology, architecture, and productivity. The earliest phenology and highest vigour and productivity were recorded in domesticated material from central Europe, characterised by short but unstressful growing seasons with reliable rainfall, long day-lengths, and rapidly rising vegetative-phase temperatures levelling out after flowering. Mediterranean habitats were classified by altitude, climate, and growing-season length. Early, productive germplasm came from warmer/low elevation sites with inconsistent rainfall and stronger terminal drought. Germplasm from low temperature/high elevation sites with high, relatively frequent rainfall had late phenology and low growth rates, early vigour, seed yield, and harvest index. Distinct habitats within the distribution range of L. luteus have selected for ecotypes with different phenologies and growth rates, which strongly influence plant architecture, fecundity and yield. It is suggested that variable responses to vernalisation and differences in seed size are important in determining these traits. European germplasm has many of the terminal drought-avoiding characteristics required in a productive Mediterranean ideotype, but may lack drought tolerance, which is likely to be under stronger selection pressure in more stressful Mediterranean habitats.