Maintenance of Parental Lines for Hybrid Red Clover1

Abstract

Seed maintenance of parental lines of red clover (Trifolium pratense L.) was examined in an I1 sib, population derived from a single clone to determine amounts of selfing and sibbing. Seeds per head produced by pseudoself‐compatibility (PSC) on uniformly heterozygous S‐allele clones under cage varied from 0 to 8.8. Twelve cages with paired leafmarked (LL or Ll) and non‐leafmarked (ll) clones produced progenies which, as shown by leafmarking, resulted more from selfing than sibbing. Cages with a high percentage of selfing produced fewer seeds than those with a high percentage of sibbing. Amount of PSC in field cages was comparable to that produced on excised stems at 40 C in the laboratory, indicating that the growing of red clover in warmer climates for PSC seed production may not be necessary. The prevalence of selfing rather than sibbing may result in high inbreeding depression manifested by loss of vigor and PSC. However, the possibility remains that selfs can be eliminated by selection and the line propagated by the remaining sibs. Further investigation of seed maintenance schemes seems justified.