EFFECT OF MAIN STEM NUMBER AND LATERAL STEM DEVELOPMENT IN POTATO PLANTS INFECTED WITH VERTICILLIUM ALBO-ATRUM AND V DAHLIAE

‘Early‐dying’ disease was examined in potato plants (King Edward) with varying numbers of main stems and lateral stems. Infection with Verticillium affected neither the number of main stems produced nor the stem number/ lateral number/yield inter‐relationships, but did slightly reduce lateral development. The host growth pattern, however, markedly influenced the severity of disease: infected plants with a single main stem or a few, compared with those having many main stems, showed delayed symptom expression and also produced many laterals which further reduced disease severity and increased longevity. Thus yield reductions as a result of infection are likely to be smaller in single‐stemmed plants showing considerable lateral development than in those plants with many main stems and few or no laterals. Copyright © 1969, Wiley Blackwell. All rights reserved