Variable paths to seed production within the Kangaroo Valley cultivar of Lolium perenne

Abstract

Components of seed yield were measured in an erect, early-flowering biotype and a prostrate, late-flowering biotype of Lolium perenne cv. Kangaroo Valley at temperatures from 15/10 to 24/19¦C (12/12 h day/night). We aimed to determine if each biotype had distinctive components of seed yield, and if these varied according to temperature. The two biotypes had distinctive paths to seed yield. Seed yield per plant in an erect biotype depended more on seed weight per spike and less on spike number than in a prostrate biotype. The distinctive paths to seed yield, and relative stability in paths across temperatures, indicated that it was possible to select genotypes from within the Kangaroo Valley cultivar which had particular correlations among components of yield. Floral development was accelerated, but seed yield per plant and most of its components were reduced, at high temperature; only the mean daily rate of dry weight accumulation by individual seeds was the same at all temperatures. At any temperature, seed weight per spike declined almost linearly with lateness of spike emergence within a plant: spikes which emerged within 21 days of the earliest spike contributed 80% of the seed yield per plant. We conclude that biotypes can be selected within the Kangaroo Valley cultivar to have distinctive components of seed yield and, based on the two biotypes we studied, commercial seed production should be based at a location having relatively low temperatures.