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CROP PHYSIOLOGY & METABOLISM

Crop Improvement and the Accumulation and Partitioning of Biomass and Nitrogen in Lentil

^a Plant Environment Laboratory, Dep. of Agriculture, The Univ. of Reading, Cutbush Lane, Shinfield, Reading, RG6 9AD, UK
^b USDA-ARS, Washington State Univ., 303W Johnson Hall, Pullman, WA 99164-6434 USA

r.j.summerfield{at}reading.ac.uk

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 representatives each of Lens orientalis (Boiss.) progenitors, landraces, pre-1980 cultivars, and modern germplasm. All 12 genotypes were sown at Pullman, WA, in 1996 and 1997, and at Reading, UK, in 1997. The biomass (all 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 seed 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 increase further in the future. Future seed yield improvement will therefore depend on increased N accumulation. Reliance on N₂ 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.

Abbreviations: DM, dry matter • FAO, Food and Agriculture Organization of the United Nations • HI, harvest index, the ratio of seed dry weight to above-ground biomass • NHI, nitrogen harvest index, the proportion of N in above-ground tissue which is found in mature seed