Ml. Desprezloustau et K. Wagner, COMPONENTS OF MARITIME PINE SUSCEPTIBILITY TO TWISTING RUST - A PATH COEFFICIENT ANALYSIS, European journal of plant pathology, 103(7), 1997, pp. 653-665
Data collected in a three-year field experiment on infection and damag
e by Melampsora pinitorqua on maritime pines showing contrasting growt
h were analysed by means of path analysis. The severity of infection i
n 2 year-old pines could be mainly explained by the amount of suscepti
ble tissues (elongating shoots). In contrast, two years later, 'intrin
sic susceptibility', i.e. expressed after inoculation, was shown to ha
ve the most important direct effect on the amount of infection. Intrin
sic susceptibility could be satisfactorily assessed by artificial inoc
ulations on excised shoots under controlled conditions. Shoot potassiu
m and phosphorous contents were shown to have marked positive effects
on susceptibility. The hypothesis of an age effect on the relative imp
ortance of different resistance mechanisms, i.e. avoidance and active
resistance, in maritime pine interaction with twisting rust is discuss
ed.