|MCGRATH, J MITCHELL|
|DE Los Reyes, Benildo|
Submitted to: Annual Beet Sugar Development Foundation Research Report
Publication Type: Other
Publication Acceptance Date: August 1, 2000
Publication Date: N/A
Technical Abstract: Aphanomyces disease is a major seedling disease in sugar beet caused by Aphanomyces cochlioides. Sixteen sugar beet breeding lines and wild species were tested for disease resistance. None of them was immune, but obvious differences were observed. Crosses were made between the susceptible line C6869 and resistant lines SP6822 and wild beet-Beta vulgaris ssp. maritima. F2 plants were inoculated with zoospores of Aphanomyces by infecting either potted plants or seedlings in petri dishes. Survival rate showed different susceptibility between different individuals within the same cross, implying the resistance may not be homozygous in resistant lines. Cytochemistry was used to study Aphanomyces infection. Both susceptible and resistant lines were infected, although the susceptible line appeared to respond slower. Three enzyme response patterns (lactate dehydrogenase, glucose-6-P dehydrogenase and peroxidase) of both lines were quite similar. The only difference observed was brownish spheres appeared on root surfaces from 1 to 12 hpi (hour post inoculation) only in resistant lines. HPLC results of tissue extracts displayed a small peak which had low retention time with high concentration at 2 hpi in resistant lines, but not in susceptible lines, suggesting these spheres contain water-soluble anti-microbial compounds. The results of lab inoculation were consistent with field performance. An F2 population for resistance segregation has been planted, and a genetic map will be constructed to find markers correlated with resistance.