Daylength responses, flowering time, and seed filling in lupins

Narrow-leafed lupin (Lupinus angustifolius) is now an established major crop in southern Australia, albus lupin (L, albus) is grown on a smaller scale, and there is interest in cultivating other lupin species. With any new crop, it is crucial that its phenology, particularly times of flowering and maturity, matches the target environment. We investigated times of flowering, maturity, and seed filling of several lupin species of agricultural interest to southern Australia. Established genotypes of L. angustifolius and L. albus flowered earliest, in 70-75 days, but L. luteus cv. Teo and some L. angustifolius lines with restricted branching matured earliest. Differences between genotypes in rates of seed filling and final seed weights meant that time of maturity was only poorly correlated with flowering time. We investigated the role of photoperiod in the timing of flowering and maturity in 12 lupin species/genotypes by: (a) growing plants under both long days in the UK and short days in Australia; and (b) growing plants under short days in Australia with or without lighting to extend the photoperiod. Flowering was clearly hastened by long days in all genotypes in both situations. However, the responses were much greater when days were naturally longer than when they were artificially lengthened. This was probably due to the illuminance requirements for perception of photoperiod by lupin not being saturated by the artificial lighting.