Blind Seed Disease

Fungal Genetics and Physiology

G. temulenta is heterothallic--it requires genetic exchange between two different mating types for sexual reproduction and subsequent production of apothecia (Griffiths 1958). G. temulenta has two mating types that are identical in all morphological features. Within each apothecium half of the ascospores are of each mating type, arbitrarily called “a” and “b.” Apothecia will develop only after mating types a and b come into contact with one another and undergo fusion.

Conidia produced following infection from an ascopore of one mating type will produce only conidia of that mating type. Genetic exchange between types can occur through transfer of macroconidia from one infected seed to another or through transfer of microconidia, which can develop on the seed in spring after the seed has overwintered. A conjugation tube--a device to exchange genetic information--can form between pairs of macroconidia even before either conidium germinates (Wilson et al. 1945). As expected from the heterothallic requirement of G. temulenta, relatively few infected seeds produce apothecia.

The vegetative hyphae are uninucleate. Chromosome number in G. temulenta is n=15, and mitotic chromosomes range in size from 0.25 to 1.0 µm. (Griffiths 1959b). In the microconidiophores the nucleolus is lacking, RNA is low, and the level of RNA depends on the level in the subtending cells (Griffiths 1959a). Microconidia have not been observed to germinate and produce a vegetative mycelium but can serve a sexual function (Griffiths 1958).

Little is known about variability in virulence of G. temulenta. Sproule and Faulkner (1974) reported variation in aggressiveness among strains of G. temulenta. Wright and Sproule (1969) reported that disease ranking of clones was the same when mixed blind seed isolates from The Netherlands or the British Isles were used.

Little is known about the physiology of G. temulenta. A cold conditioning period of about 8 weeks is required to induce the apothecial phase. The metabolic pathways or mechanism associated with the induction have not been investigated.

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United States Department of Agriculture
Agricultural Research Service

The material on this page is in the public domain.

Original posting: October 2001.