Allelopathy in Rye (Secale cereale)

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Title: Allelopathy in Rye (Secale cereale)
Author: Brooks, Ashley Meredith
Advisors: Jeff Thompson, Committee Member
David A. Danehower, Committee Chair
Chris Reberg-Horton, Committee Member
J. Paul Murphy, Committee Member
Abstract: Allelopathy is an ecological phenomenon in which chemicals produced by and released from a plant affect the germination or growth of another plant. A possible exploitation of allelopathy is the use of allelopathic cover crops for weed management. Organic farming systems can utilize allelopathy as an alternative to synthetic herbicides and conventional farming can reduce reliance upon pre-emergence herbicides. Rye (Secale cereale) is a cover crop species known to be allelopathic to many weeds. In addition to allelopathic activity, rye is a successful cover crop because of prolific biomass, high germinability and winter hardiness. The objective of this research was to investigate the potential to develop a rye cultivar with increased allelopathy through a conventional breeding approach. A population of 150 half-sib families of rye was grown in two North Carolina locations. Above ground tissue was utilized to assess rye allelopathic activity. To assess allelopathy in the population, we aimed to develop a greenhouse bioassay which utilized a rye incorporated soil media and redroot pigweed (Amaranthus retroflexus) as the indicator species. It is necessary to identify a screening protocol to quantify variation in allelopathic activity and to identify high performing lines. The greenhouse bioassay was fast, inexpensive and able to screen the large number of genotypes in the rye population. Results of redroot pigweed fresh weight biomass were reproducible and were utilized to estimate genetic parameters for allelopathy in the rye population. Estimates of genetic variation, genotype x environment interaction and narrow sense heritability help plant breeders develop an appropriate breeding program for the trait of interest. The estimates also give an idea of the rapidity at which progress can be made with selection. Genetic variation for rye allelopathy was not significant across locations but was significant within each location. Redroot pigweed fresh weight biomass was normally distributed indicating that allelopathy in rye is a quantitative trait. Heritability estimates were low on a per-plot basis and moderately low on an entry mean basis. A petri dish bioassay was also utilized to estimate genetic parameters for allelopathy in rye. Redroot pigweed germination and root length measures were utilized to quantify allelopathic activity. Genetic variation was not significant across locations for germination or root length. Analysis of variance within each location detected variation among the genotypes grown at the Kinston location but not at the Clayton location. Measures of redroot pigweed germination and root length were normally distributed. Heritability estimates were low on a per-plot basis and on an entry mean basis. This study demonstrates that allelopathy in rye is under genetic control and that it is a quantitative trait. Results suggest that a conventional breeding approach may be used for the development of a highly allelopathic rye cultivar.
Date: 2008-12-05
Degree: MS
Discipline: Crop Science

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