| ||Title Page|
| ||Table of Contents|
| ||List of Figures|
| ||List of Tables|
| ||Part I: Literature review|
| ||Part II: Section No. 1. Mechanical...|
| ||Part II: Secion No. 2. Correlation...|
| ||Part III: Appendix No. 1. The influence...|
| ||Part III: Appendix No. 2. Preconditioning...|
| ||Biographical sketch|
| Material Information
||Physical and chemical properties of resistance exhibited by certain genotypes of Arachis hypogea to invasion by aflatoxin producing Aspergillus spp.
||77 leaves : ill. ; 28 cm.
||LaPrade, Jesse Cobb, 1941-
||Subjects / Keywords:
||Plant Pathology thesis Ph. D
Peanuts -- Breeding ( lcsh )
Peanuts -- Diseases and pests ( lcsh )
Dissertations, Academic -- Plant Pathology -- UF
||bibliography ( marcgt )
non-fiction ( marcgt )
||Data froK inoculations of whole, shelled peanuts from 165 Florida
breeding 3.ines with conidia from three isolates of the Aspergillus
flavus group (N.R.R.L. 3794, N.R.R.L. 2999, and one Florida isolate)
revealed statistically significant differences in tolerance to colonization
by the fungus. If seed coats were punctured with a needle or
abraded with carborundum before inoculation there were no significant
differences in tolerance among the lines. When intact seeds were soaked
in an aqueous solution of 1.0 per cent 2, 3, 5-triphenyl-2H-tetrazoliuni
diloride (T.Z.C.), a uniform reduction of T.Z.C. occurred on the cotyledons
of the susceptible lines but not those of the tolerant lines.
This suggested that the seed coats of the tolerant lines were not as
permeable as those of the susceptible lines. Aqueous extracts of intact
seeds of both tolerant and susceptible lines stimulated' germination of A. flavus conidia when compared to conidia incubated in distilled water.
Diethyl ether extracts of intact seeds of tolerant peanut lines revealed
no germination inhibition when compared with conidia incubated in
distilled water. Thus an intact testa was required for tolerance and
appeared to function as a mechanical barrier to penetration by the fungus.
Wax- like accumulations were noted in scanning electron micrographs
on the testes of dried peanut seed. Seeds from breeding lines which
were tolerant to colonization by Aspergillus flavus (N.R.R.L. 2999)
appeared to possess more of the wax-like accumulations than did several
which were highly susceptible. Extraction of waxes and lipids from
Intact seeds with dilorofom: methanol, 2:1 (v/v) , for up to 5 minutes
increased the susceptibility of the extracted seeds. No reduction
in germination percentage of the seed extracted for 5 minutes was
noted. A suspension of A. flavus conidia was placed on the dried
solvent residue from a 5 minute and a 2 hour extraction of intact
tolerant peanut seed. Germination of A. flavus conidia was slightly
stimulated by the residue, compared to distilled water. It appears
that the wax-like accumulations help prevent A. flavus from penetrating
the intact seed coat.
Several preconditioning factors that fluctuate under ordinary
gracing and storage conditions were shown to affect the tolerance
expressed by two tolerant breeding lines and the moderately tolerant
Florunner variety. Pod rot caused primarily by severe nematode infections
on Florunner peanuts led to higher levels of aflatoxin contamination
under field conditions compared with pod ret caused primarily by fungi. Peanuts of a tolerant breeding line dug 5 weeks before or 1 week
after inoculation were more susceptible than peanuts dug at optimum
maturity. Tolerance was lost after 1 year of storage of shelled
peanuts coTipared with non-shelled peanuts of the same tolerant genotype,
The term tolerance as used throughout this context refers to a
variable level of infection by fungi of the A. flavus group on peanuts
of breeding lines and cultivars. This term was used to differentiate
the reaction observed in this study from a hyper sensative reaction.
||Thesis--University of Florida, 1973.
||Includes bibliographical references (leaves 69-76).
||Statement of Responsibility:
||by Jesse Cobb LaPrade.
| Record Information
||University of Florida
||University of Florida
||All rights reserved by the source institution and holding location.
||alephbibnum - 000413910
oclc - 37852566
notis - ACG1044
|Table of Contents
Table of Contents
List of Figures
List of Tables
Part I: Literature review
Part II: Section No. 1. Mechanical tolerance of selected genotypes of dried peanuts to colonization by strains of Aflatoxin producing Aspergillus spp
Part II: Secion No. 2. Correlation of peanut seed coat surface wax accumulations with tolerance to colonization by Aspergillus flavus
Part III: Appendix No. 1. The influence of peanut moisture content on the reliability of the screening technique used to determine tolerance of breeding lines
Part III: Appendix No. 2. Preconditioning factors affecting colonization by Aflatoxin producing Aspergillus spp