Relationship of inoculum of Verticillium dahliae to disease in tomato plants
1981
Visser, S. | Hattingh, M.J. (Horticultural Research Inst., Pretoria (South Africa))
Tomato (Lycopersicon esculentum Mill.) seedlings were inoculated by dipping roots in suspensions of conidia of Verticillium dahliae Kleb. There was a linear relationship between inoculum concentration and infection at 21 days after inoculation in steam-disinfected soil. Thereafter the number of infections per plant increased. At higher concentrations data indicated a synergistic interaction between conidia. Synergism was more pronounced and was detected earlier in soil not disinfested before inoculation. When conidia from 3-, 7-, and 14-day-old cultures were used, the greater response was from 3-day-old cultures. A lower total response and lower rate of response to older inoculum indicated a decrease in aggressiveness of conidia with age. Older plants were less affected by the pathogen when plants inoculated at the fourth and sixth leaf stages with minimum root disturbances were compared. There was also an increase in infection with an increase in the volume of root zone infested. In field experiments infection reduced stand when roots were disturbed at inoculation. With minimum root disturbance yields were reduced without a reduction in stand.
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