Life-table analysis of faba bean rust

Abstract

In controlled near-optimum conditions (18 ~ monocyclic sporulation capacity and spore infection efficiency were assessed for faba bean rust on the first and second leaves of field bean. After a latency period of 8-10 days, lesions sporulated during c. 50 days. Spore production on the second leaf, c. 9 • 104 spores per lesion, was two times as high as spore production on the first leaf. Infection efficiency was similar for both leaf layers, with a mean value of 0.11 lesion per inoculated spore. Infection efficiency decreased strongly when spores originated from mother lesions older than 20 days. Three lifetable statistics (the net reproduction number Ro, the mean generation time T 8, and the maximum relative growth rate r,,o~) were calculated. Ro was larger and Tg was longer for the second than for the first leaf, but rmax was nearly the same for both leaf layers (0.31-0.33 day-l), rma x was compared with the exponential growth rate r measured in a field experiment. From the difference between the two rates, the fraction of inoculum lost in field conditions was estimated at 0.54-0.94. The life-table statistics were also compared to those of other legume rusts, and implications of life-table analysis for comparative epidemiology were discussed.

Are green islands red herrings? Significance of green islands in plant interactions with pathogens and pests

“…suggests that, ceteris paribus , an increase in T g will decrease fitness. Data on a number of rusts of legume hosts (Sache & Zadoks, 1995) support this view (Fig. 10).…”

“… The relationship between pathogen fitness and mean generation time (days from infection to production of new spores for a polycyclic pathogen) for several rust pathogens of leguminous hosts. Data from Sache & Zadoks (1995). The fitness value λ in the figure is calculated as λ = exp( r max ) (see Caswell, 2001), with r max (maximum relative growth rate, expressed as the number of daughter lesions per mother lesion per day) values taken from Sache & Zadoks (1995).…”

“…Data from Sache & Zadoks (1995). The fitness value λ in the figure is calculated as λ = exp( r max ) (see Caswell, 2001), with r max (maximum relative growth rate, expressed as the number of daughter lesions per mother lesion per day) values taken from Sache & Zadoks (1995).…”

“…Is the proposed role of green islands in maintaining a supply of nutrients for the pathogen likely to provide a fitness gain sufficient to offset the metabolic cost? The answer is unknown, but spore production curves tend to reach a maximum relatively early in the infectious period of a pathogen (Teng & Close, 1978;Rouse, Mackenzie & Nelson, 1984;Sache & Zadoks, 1995;Sache, 1997) and the infection efficiency of spores produced by lesions decreases with lesion age (see Fig. 2 in Sache & Zadoks, 1995).…”

Screening techniques and sources of resistance to rusts and mildews in grain legumes

“…A prolonged LP seems to be the most influential component in the epidemic process. Reduced IF, spore production (number of spores produced per pustule per day) or duration of sporulation (number of days of spore production per pustule) are other important components of resistance (Habtu & Zadoks, 1995;Sache & Zadoks, 1995;Sillero et al, 2000;Singh et al, 2003). These parameters expressed in polycyclic situations increase the differences between susceptible and resistant lines.…”