Crop improvement and the accumulation and partitioning of biomass and nitrogen in lentil

Domestication and subsequent genetic enhancement in lentil (Lens culinaris Medik.) have involved changes in plant structure and DM distribution. These changes were examined using a "genetic gradient" comprising three represen tatives each of Lens orientalis (Boiss.) progenitors, landraces, pre-1980 c ultivars, and modern germplasm, All 12 genotypes were sown at Pullman, WA, in 1996 and 1997, and at Reading, UK, in 1997, The biomass fall genotypes) and N concentration (four genotypes) of above-ground tissues were measured at 50% flowering (leaf and stem) and at reproductive maturity (leaf, stem, pod wall and seed). The progenitors produced meager biomass (averaging 0.72 Mg ha(-1)) and poor HI (0.19). and consequently small seed yields (0.11 Mg ha(-1)). Productive landraces had substantially higher biomass (3.52 Mg ha (-1)), improved HI (0.34), and larger seed yields (1.13 Mg ha(-1)). Biomass and seed yield were increased further by the selection of cultivars: (5.11 and 1.32 Mg ha(-1), respectively). The development of modern germplasm by hybridization further increased seed yields (1.95 Mg ha(-1)). Consistent se ed yield improvements have not been associated with consistent increases in HI. Instead a strong, positive correlation between seed yield and biomass has persisted. NHI increased more rapidly than HI and is unlikely to increa se further in the future. Future seed yield improvement will therefore depe nd on increased IU accumulation. Reliance on N-2 fixation must be supported by increased photosynthetic capacity and therefore by vegetative biomass. An advantageous correlation between seed yield and residue production seems likely to persist as crop improvement continues.