Residual gene resistance using the crown rust of oats pathosystem
Windes, Juliet M.
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Permalink
https://hdl.handle.net/2142/21088
Description
Title
Residual gene resistance using the crown rust of oats pathosystem
Author(s)
Windes, Juliet M.
Issue Date
1992
Doctoral Committee Chair(s)
Pedersen, Wayne L.
Department of Study
Crop Sciences
Discipline
Crop Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Plant Pathology
Language
eng
Abstract
Residual gene resistance has been described as the effect of race-specific resistance genes in the host plant when the host is inoculated with a pathogen lacking the corresponding avirulence genes. Pyramiding resistance genes may produce durable, effective resistance against many pathogen races. This hypothesis was tested in three experiments using the crown rust of oats pathosystem.
In the first experiment, eight nearly isogenic oat lines, Avenae sativa L., each homozygous for one to four resistance genes to crown rust (Pruccinia coronata f.sp. avenae or P.c.a.), were compared to the recurrent parent for residual gene resistance. Latent period, pustule length, daily spore production, and total pustule number per leaf were determined. There was a significantly shorter latent period for X465 than for the recurrent parent. One isoline, X864, produced significantly fewer spores than the recurrent parent. These results do not support the residual resistance hypothesis. The responses may be due to genes other than the resistance genes that were transferred in the backcross program in isoline development.
In the second experiment, four F$\sb1$ hybrids were obtained by crossing the eight susceptible, nearly-isogenic oat lines. No significant differences were seen among the recurrent parent, C.I. 8044, and the F$\sb1$ hybrids for latent period, daily spore production, pustule length, or pustules per leaf.
In order to reduce the coefficients of variation and to increase the experimental sensitivity, the first experiment was repeated in a detached leaf assay. Latent period, pustules per leaf, pustule length, and pustule area were measured. The responses did not support the residual resistance hypothesis. There was a reduction in the coefficients of variation for all measurements. Correlations between the whole plant experiment and the detached leaf assay for the above components of resistance were not significant. Results from the detached leaf assay were different from the whole plant, but consistently produced infection and could be used to determine infection type.
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