Temperature and Effects of Seed‐borneBotrytis cinereaorAlternaria linicolaon Emergence of Linseed (Linum usitatissimum) Seedlings

Abstract

Experiments were done at temperatures from 5 to 20 degrees C to investigate the effects of infection of linseed seed (cv. Antares) by Botrytis cinerea or Alternaria linicola on seedling emergence and to study transmission of the pathogens from seed to seedlings. In one experiment with freshly harvested seed, the maximum percentage emergence decreased linearly as the incidence of B. cinerea in seed increased from 0 to 83% at 18 degrees C day/12 degrees C night temperatures. In another experiment, the decrease in percentage emergence of seed associated with infection by B. cinerea, the transmission of the pathogen to seedlings to produce disease symptoms on their hypocotyls and the incidence of post-emergence death all increased as temperature decreased from 20 to 5 degrees C. However, the decrease in percentage emergence of seed associated with infection by A. linicola and the transmission of the pathogen to seedlings to produce cotyledon lesions both increased as temperature increased from 5 to 20 degrees C. There was little effect of either pathogen on the time from sowing to 36% of maximum emergence, which decreased with increasing temperature. In a subsequent experiment at 10 degrees C comparing seed infected with B.cinerea or A. linicola, using the same seed sources as in the previous experiments, infection by A. linicola decreased emergence more than infection by B. cinerea, even though the incidence of A. linicola in the seed was smaller. Analyses of position and parallelism suggested that regressions of maximum percentage emergence (logit-transformed) against temperature were fitted best by non-parallel lines for seed infected by B. cinerea or A. linicola

Analysis of Cryptic, Systemic Botrytis Infections in Symptomless Hosts

“…Specialist Botrytis species such as B. aclada and B. allii have been understood to have a life-cycle involving extended periods of symptomless growth (Maude and Presly, 1977 ; du Toit et al, 2004 ). Seed infection by species in the B. cinerea complex leading to seedling infection has been well-known for some time in species such as linseed (Harold et al, 1997 ) because of its contribution to seedling death. It has been less appreciated that long-lived cryptic infection with generalist Botrytis is possible.…”

Persistent, symptomless, systemic, and seed-borne infection of lettuce by Botrytis cinerea

“…However, where it then progresses to the germinating seedling, it has usually been reported to cause a seedling blight, as for example in linseed and chickpea (Burgess et al, 1997;Harold et al, 1997), and then progresses polycyclically in the developing crop. In the work reported here, seed contamination leading to systemic infection was shown very clearly in the 2004 glasshouse experiment, in which seed surface-sterilisation substantially reduced infection of plants at 2 MAP and directly by the frequent recovery of infected plants from seed sown in the isolation plant propagator.…”

“…Seed infection by B. cinerea leading to disease is known in several species, including for example linseed (Linum usitatissimum) (Harold et al, 1997), chickpea (Cicer arietinum) (Burgess et al, 1997) and lentil (Huang and Erickson, 2005). In most cases it is reported because the infection causes seedling mortality and the dead seedlings provide a source of inoculum for the surviving crop.…”

Factors affecting the development of Botrytis cinerea (grey mould) on linseed (Linum usitatissimum) buds, flowers and capsules

“…Infections occurring at these two susceptible stages account for high proportions of the yield losses associated with grey mould on linseed (Mercer et al, 1994). Losses occur firstly as a result of abscission of affected buds at late flowering before capsules are formed and secondly because many capsules with grey mould fail to set seed, fall off before harvest or produce shrivelled seed that is not harvested because it is sieved out (Harold et al, 1997). Remaining affected capsules may produce seed contaminated with B. cinerea, which is an important consideration for a seed crop (Anon., c).…”

“…red raspberry (Rubus idaeus L.), are particularly susceptible to B. cinerea infection during flowering (McNicol et al, 1985). B. cinerea may be transmitted from infected linseed seed to emerging seedlings, but after the seedling stage there are generally few symptoms of grey mould observed until flowering and capsule development (Harold et al, 1997), unless crops are damaged or lodged. It is important to understand how changes in susceptibility of linseed plants to infection by B. cinerea during the growth of the plant influence the epidemiology of grey mould disease.…”