Evidence implicating the lipoxygenase pathway in providing resistance to soybeans against Aspergillus flavus

The fungus, Aspergillus flavus, secretes lipases while parasitizing oilseed hosts and may contaminate the seed with aflatoxin. We found that exogenous lipase applied to soybean cotyledons results in the generation of volatile aldehydes by the lipoxygenase pathway that halts the growth of fungi. Vola...

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Bibliographic Details
Published in:Phytopathology 1993-12, Vol.83 (12), p.1473-1477
Main Authors: Doehlert, D.C, Wicklow, D.T, Gardner, H.W
Format: Article
Language:English
Subjects:
Agronomy. Soil science and plant productions
ALDEHIDOS
ALDEHYDE
ASPERGILLUS FLAVUS
Biological and medical sciences
BIOSINTESIS
BIOSYNTHESE
COMPOSE VOLATIL
COMPUESTO VOLATIL
Fundamental and applied biological sciences. Psychology
Genetics and breeding of economic plants
GLYCINE MAX
LIPOXIGENASA
LIPOXYGENASE
Pest resistance
Plant pathogens
RELACIONES HUESPED PARASITO
RELATION HOTE PARASITE
RESISTANCE AUX MALADIES
RESISTENCIA A LA ENFERMEDAD
SECRECIONES DE LAS PLANTAS
SECRETION VEGETALE
TRIACILGLICEROL LIPASA
TRIACYLGLYCEROL LIPASE
Varietal selection. Specialized plant breeding, plant breeding aims
VIA BIOQUIMICA DEL METABOLISMO
VOIE BIOCHIMIQUE DU METABOLISME
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Summary:The fungus, Aspergillus flavus, secretes lipases while parasitizing oilseed hosts and may contaminate the seed with aflatoxin. We found that exogenous lipase applied to soybean cotyledons results in the generation of volatile aldehydes by the lipoxygenase pathway that halts the growth of fungi. Volatiles generated from untreated homogenized soybeans did not affect the germination of A. flavus spores in a closed petri plate assay in which spores were streaked on corn-meal agar and soybean homogenate was placed on the lid of the inverted plate. When lipase (500 units/ml) was added to the soybean homogenate, all fungal spore germination was inhibited. However, the addition of nordihydroguaiaretic acid (a lipoxygenase inhibitor) to the soybean homogenate/lipase mixture partially reversed the inhibition of spore germination. The extent of spore germination was dependent on both the number of soybean cotyledons in the homogenate and the activity of the added lipase. Addition of linoleic or linolenic acids to the homogenates also inhibited spore germination, whereas palmitic, stearic, or oleic acid had no effect, compared to untreated homogenates. Headspace analysis indicated that hexanal, a product of the lipoxygenase pathway with known antifungal activity, was the major volatile generated from lipase-treated homogenates. Soybeans are exceptional among oil-rich seed crops in that they are resistant to A. flavus infection and aflatoxin contamination. Our evidence strongly suggests that the lipoxygenase pathway may contribute to this resistance
ISSN:0031-949X
1943-7684
DOI:10.1094/Phyto-83-1473