addition of 1 -percent peptone to PDA or malt agar 

 increases spore mucilage production (Calvert and 

 Muskett 1945). However, some cultures are predomi- 

 nantly mycelial while others are conidial (Wilson et 

 al. 1945). 



In culture, macroconidia are produced from short 

 conidiophores formed at intervals perpendicular to the 

 hypha (Calvert and Muskett 1945, Wilson et al. 1945). 

 Conidia from culture may be larger (Wilson et al. 

 1945) or appear less regular than those from seed 

 (Calvert and Muskett 1945). Growth is slow at 5 °C, 

 optimal at about 20 °C, less at 27 °C, and restricted at 

 30 °C (Neill and Hyde 1939, Alderman 1992). Radial 

 growth slows with decreasing water potential through 

 -9.0 to -1.0 MPa (Alderman 1992). 



Sporodochia develop in culture at 5 °C to room 

 temperature after about 1-3 months (Calvert and 

 Muskett 1945). Growth characteristics on various 

 media were described by Neill and Hyde ( 1939) and 

 Calvert and Muskett (1945). 



Similar-Looking Fungi 



Calvert and Muskett (1945) collected other 

 discomycetes associated with ryegrass and detritus 

 that are similar to G. temulenta but differ in morphol- 

 ogy in culture and do not produce spores. Unfortu- 

 nately, neither species identification nor technical 

 descriptions of these other fungi were recorded. 



Neill and Hyde (1939) found a fungus on Lolium that 

 is similar to G. temulenta. They defined it as Lolium 

 fungus number 2. Unfortunately, the taxonomic 

 description and species identity of this fungus was not 

 established either. 



Biology and Epidemiology 



Overwintering and Production of Apothecia 



The general life cycle of G. temulenta is illustrated in 

 figure 14. The overwintering, or survival, unit of G. 

 temulenta is the infected seed. Infected seeds reach the 

 soil by shattering, by seed loss during harvest opera- 

 tions, by planting of diseased seeds, and by natural 

 seed dispersal in harvested areas (Hardison 1945). 

 Infected, ungerminable seeds resist attack by bacteria 

 and molds and do not decay as they overwinter (Neill 

 and Hyde 1939; Calvert and Muskett 1944. 1945). 

 At or near the soil surface, G. temulenta continues to 

 develop within the seed. Moist soil conditions with 

 temperatures near 2 °C for about 8 weeks are required 



to induce the sexual (apothecial) stage of G. temulenta 

 (Griffiths 1958). The precise biochemical changes that 

 occur or metabolic pathways affected during this 

 conditioning have not been determined. 



In spring or early summer, at or prior to flowering of 

 perennial ryegrass, apothecia emerge from the over- 

 wintering infected seeds (Calvert and Muskett 1945, 

 Wilson et al. 1945). Usually one to three, but as many 

 as seven, apothecia can emerge from a single infected 

 seed (Gray 1942, Calvert and Muskett 1945). Not all 

 infected seeds will yield apothecia. In fact, only 5-30 

 percent of ungerminated seed produce apothecia 

 (Calvert and Muskett 1945, Griffiths 1958). 



Production and Release of Ascospores 

 (Primary Inoculum) and Primary Infection 



Large numbers of ascospores are ejected from each 

 apothecium in response to slight changes in relative 

 humidity (Calvert and Muskett 1945). In New 

 Zealand, spore release occurs between early Novem- 

 ber and middle December, with peak numbers coin- 

 ciding with flowering in perennial ryegrass (Neill and 

 Armstrong 1955). Most spores are airborne between 

 10:00 a.m. and 2:00 p.m. (Johnston et al. 1965). 



Ascospores that land on flowers, including the stigma, 

 ovary, or styles, will germinate and infect the host. 

 However, seeds can be infected up to the time they 

 reach their maximum size (Hyde 1937). 



Secondary Infection 



Within about 7 days (Hyde 1937, 1945: Wilson et al. 

 1945) to 16-17 days (Calvert and Muskett 1945) after 

 inoculation, the conidial stage is manifest — a pinkish 

 slime in which conidia are embedded. These spores 

 are relatively short-lived, about 1 month (Cunningham 

 1941, Neill and Hyde 1942). However, a few conidia 

 may survive as long as 4-6 months if stored under 

 cool, dry conditions (Calvert and Muskett 1945). 



Disease Development and Spread 



Wet seasons, especially during anthesis in the grasses, 

 are clearly supportive of blind seed infection (Foy 

 1927; Gorman 1940; Osborn 1947; Blair 1947. 1948; 

 Lithgow and Cottier 1953; Chestnutt 1958; de Tempe 

 1966; Grant 1985). Based on field surveys in New 

 Zealand. Lithgow and Cottier ( 1953) found that 

 districts which produced ryegrass seed with high 

 germination (low blind seed disease) had less than 

 half the rain days during flowering than districts 

 producing seed with low germination. Hardison 



13 



