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Master
Etats Unis
1969
SOME RHIZOCTONIA SOLANI (KUEHN)-ALFALFA (MEDICAGO SATIVA L.) RELATIONSHIPS
Titre : SOME RHIZOCTONIA SOLANI (KUEHN)-ALFALFA (MEDICAGO SATIVA L.) RELATIONSHIPS
Auteur : El-Khash, Mohammed Najib,
Université de soutenance : University of Arizona
Grade : Master of Science (MS) 1969
Résumé
Rhizoctonia solani (Kuehn) persisted as a pathogen
in alfalfa for about one year, and progressed from the
plant roots to the shoots. Four cultivars of alfalfa were
found equally susceptible to the fungus.
Growth studies showed that minimum growth of 6
isolates occurred at 20 C, and optimal growth of most of
them occurred at 26 C. Of the combinations of 18 nitrogen
and 11 carbon sources used, maximum growth of the fungus
occurred on fructose/L-asparagine, and minimum growth
occurred on C/N combinations containing DL-aspartic acid,
L-glutamic acid, L-histidine HC1, and DL-tryptophane as
nitrogen sources.
The virulence of Rhizoctonia was not influenced by
pre-culturing it on various C/N concentrations.
Rhizoctonia grew in various directions over the
surface of alfalfa roots. Penetration of roots occurred
more commonly from branches arising from single hyphae,
and was effected on the same host by either normal hyphal
branches or infection pegs. Invaded epidermis and cortical
tissues collapsed at later stages in disease development,
but the fungus did not advance to the central cylinder. Five Streptomyces spp. reduced severity of lesions
caused by Rhizoctonia. No significant difference was
found between seed inoculation or soil infestation with
the antibiotic producers.
Page publiée le 20 février 2018