Selection for Allelopathy in Rye (S. cereale).

Allelopathy is the release of toxic chemicals by a donor plant species, which inhibit or suppress the growth and germination of a receiver plant species.  Variation in allelopathy has been observed in rye (Secale cereale), which suggested that improvement through conventional breeding methods may be successful.  The objectives of this research were:  1) to develop a reliable greenhouse protocol for screening allelopathy among large numbers of segregating rye genotypes, and 2) to obtain estimates of genetic variance and heritability for the allelopathy trait in rye.  One hundred and fifty random half-sib families were grown at two locations during the 2006-07 season in North Carolina.  Half-sib families were cut at ground level at the boot stage and oven dried.  Ground field tissue of each half-sib family was mixed with soil media.  A known number of redroot pigweed (Amaranthus retroflexus) and large crabgrass (Digitaria sanguinalis) seeds were planted into the mixture.  Redroot pigweed and large crabgrass counts and fresh weights were quantified as allelopathy measures. All measures displayed normal distributions indicating allelopathy is a quantitative trait. There was significant genotype x location interaction.  Genetic variation among half-sib families was significant for all measures of weed control.   Estimates of narrow sense heritability ranged from 0.02 to 0.20 on per plot basis and 0.16 to 0.33 on a family mean basis.  Standard errors for heritability were 0.08 on a per plot basis and ranged from 0.11 to 0.13 on a family mean basis. The greenhouse protocol was successful in handling the large number of genotypes for screening allelopathy.  The protocol eliminated physical interference so that weed suppression could be attributed to allelopathy.