LIFE-TABLE ANALYSIS OF FABA BEAN RUST

In controlled near-optimum conditions (18 degrees C), monocyclic sporu lation capacity and spore infection efficiency were assessed for faba bean rust on the first and second leaves of field bean. After a latenc y period of 8-10 days, lesions sporulated during c. 50 days. Spore pro duction on the second leaf, c. 9 X 10(4) spores per lesion, was two ti mes as high as spore production on the first leaf. Infection efficienc y was similar for both leaf layers, with a mean value of 0.11 lesion p er inoculated spore. Infection efficiency decreased strongly when spor es originated from mother lesions older than 20 days. Three life-table statistics (the net reproduction number R(o), the mean generation tim e T-g, and the maximum relative growth rate r(max)) were calculated. R (o) was larger and T-g was longer for the second than for the first le af, but r(max) was nearly the same for both leaf layers (0.31-0.33 day (-1)). r(max) 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 le gume rusts, and implications of life-table analysis for comparative ep idemiology were discussed.