A study of some of the inter-relationships between maize and the seed storage fungi as typified by Aspergillus flavus var. columnaris.
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Date
1990
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Abstract
The seed storage fungi (xerotolerant) species of the genera
Aspergillus and Penicillium} are renowned for their devastating
effects on stored grain and grain products. In view of the fact
that most of these fungi Iiberate toxins which can be harmful to
both man and his livestock this problem is becoming increasingly
relevant, particularly in developing countries. The seed storage
fungi are said to be saprophytes and opportunistic invaders of
dead or naturally dried organic matter, and as such no direct
host-pathogen relationship has been ascribed to them. This
dissertation reports aspects of an investigation into the
modes/pathways utilised by these fungi in their infection of maize
caryopses (seeds) and plants. The work involved studies on: the
effects of protracted storage on maize seeds; the morphology of
storage fungi; extra-cellular enzymes of storage fungi; the
pathways utiIised by the storage fungi in invasion of seed tissues;
and the effects of the storage fungi on the seeds. Correlations
have been made on a species basis between the extent of seed
deterioration and fungal aggressiveness. The results of these
investigations indicated that apart from affecting seed vigour and
viability, these fungi can also affect plant vigour. This latter
aspect was further investigated to determine whether a seed
storage fungus could infect germinating maize seeds, and remain
an internal contaminant of the tissues during plant growth and
development. These latter studies revealed that Aspergillus flavus
var. columnaris is capable of systemic transmission from one seed
generation to the next. This hitherto unrecognised phenomenon
apart from indicating that the fungal species is in fact a biotroph
as well as a saprophyte, also has implications In control
measures.
Description
Thesis (Ph.D.)-University of Natal, Durban, 1990.
Keywords
Aspergillus., Seeds--Physiology., Seeds--Storage., Theses--Biology.