Domestication bottlenecks limit genetic diversity and constrain adaptation in narrow-leafed lupin (Lupinus angustifolius L.)

Abstract

In contrast to most widespread broad-acre crops, the narrow-leafed lupin (Lupinus angustifolius L.) was domesticated very recently, in breeding programmes isolated in both space and time. Whereas domestication was initiated in Central Europe in the early twentieth century, the crop was subsequently industrialized in Australia, which now dominates world production. To investigate the ramifications of these bottlenecks, the genetic diversity of wild (n = 1,248) and domesticated populations (n = 95) was characterized using diversity arrays technology, and adaptation studied using G × E trials (n = 31) comprising all Australian cultivars released from 1967 to 2004 (n = 23). Principal coordinates analysis demonstrates extremely limited genetic diversity in European and Australian breeding material compared to wild stocks. AMMI analysis indicates that G × E interaction is a minor, albeit significant effect, dominated by strong responses to local, Western Australian (WA) optima. Over time Australian cultivars have become increasingly responsive to warm, intermediate rainfall environments in the northern WA grainbelt, but much less so to cool vegetative phase eastern environments, which have considerably more yield potential. G × E interaction is well explained by phenology, and its interaction with seasonal climate, as a result of varying vernalization responses. Yield differences are minimized when vegetative phase temperatures fully satisfy the vernalization requirement (typical of eastern Australia), and maximized when they do not (typical of WA). In breeding for WA optima, the vernalization response has been eliminated and there has been strong selection for terminal drought avoidance through early phenology, which limits yield potential in longer season eastern environments. Conversely, vernalization-responsive cultivars are more yield-responsive in the east, where low temperatures moderately extend the vegetative phase. The confounding of phenology and vernalization response limits adaptation in narrow-leafed lupin, isolates breeding programmes, and should be eliminated by widening the flowering time range in a vernalization-unresponsive background. Concomitantly, breeding strategies that will widen the genetic base of the breeding pool in an ongoing manner should be initiated.

Legume Crops Phylogeny and Genetic Diversity for Science and Breeding

“…Domestication began in earnest at the start of the twentieth century with the development of sweet (low-alkaloid) cultivars in Germany, Poland and Russia (Wolko et al, 2011). The process of domestication was completed in Australia through the incorporation of pod indehiscence, soft-seededness and early flowering (removal of vernalization responsiveness) genes (Berger et al, 2012a). Australian sweet cultivars contain a recessive gene for white flower and seed color that distinguishes them from bitter, blue-flowered wild types.…”

“…Due to its recent domestication the current focus is on collecting wild diversity. (Talhinhas et al, 2003(Talhinhas et al, , 2006González-Andrés et al, 2007;Raman et al, 2008;Sbabou et al, 2010;Nelson et al, 2011;Berger et al, 2012a). Systematic investigations that integrate both molecular and ecophysiological information are required for all four cultivated Lupinus species.…”

“…L. albus collection site climates are more complex than those of L. angustifolius and L. luteus, including low rainfall sites in central Anatolia, very warm irrigated locations along the Nile River Valley, and warm and wet locations in the Ethiopian highlands (Berger et al, 2008b). Recent genotype by environment interaction studies highlighted the limited adaptive and genetic diversity of modern elite cultivars, demonstrating that matching cultivar phenology to target environment (late for long season, early for short season) was not possible throughout much of the current production range because of a confounding between vernalization response and later flowering (Berger et al, 2012a, b). The idea that lupin yield could be increased by selecting appropriate adaptive traits for specific target environments has sparked interest in the adaptive strategies of wild germplasm, which, unlike domesticated material, has undergone natural selection in the contrasting Mediterranean environments described above.…”

“…A simplified version of this approach, whereby European cultivars acted as donors, appeared to be even more effective, with up to 44% higher yields than the recurrent Australian variety . However, given the close genetic relationship between Australian and European breeding material, it is likely that such gains will be less sustainable compared to introgressive crossing with the much more diverse wild germplasm (Berger et al, 2012a). In addition to their role in increasing yield, these genetically diverse populations will be grown in multi-environment trials to study specific adaptations in a domestic framework, linking adaptive traits to QTLs where possible.…”

The future of grain legumes in cropping systems

“…In common bean, for example, climbing-type cultivars with delayed flowering and continued production of leaves after flowering commonly out-yield bushtype cultivars with early flowering (Clark and Francis 1985;Kornegay et al 1992). Of course, delayed maturity and large leaf area can be counterproductive in environments with lateseason drought or adverse temperature (Berger et al 2012). For example, larger leaf area development can result in rapid water use under terminal drought conditions where water savings may be necessary in chickpea (Zaman-Allah et al 2011a) and cowpea (Belko et al 2012).…”