Effects of Pseudopeziza leaf spot disease on growth and yield in lucerne

Abstract

Growth analysis of lucerne plants infected with Pseudopeziza medicaginis compared with growth analysis of healthy plants showed that, while infection caused a general decrease in relative growth rate and leaf area ratio and affected the relative proportions of leaf, stem and root, there was no overall change in the growth pattern during the experimental period (7 weeks). In addition to retarding the net assimilation rate in leaves and roots, infection did slow down the rate of increase of net assimilation rate in leaves as well as its rate of decrease in roots. Infection delayed and possibly reduced flowering. Glasshouse, phytotron and field trials showed that infection with P. medicaginis can reduce dry matter production in lucerne by over 40%. It was shown that, in the absence of fresh infections, the influence of a single period of infection can have a considerable long-term effect.