The influence of potato cyst nematodes (Globodera pallida) and drought on rooting dynamics of potato (Solanum tuberosum L.)

Minirhizotron root video observations of two experiments (in 1991 and 1992) in the Wageningen Rhizolab were used to investigate the extent to which po tato cyst nematodes (Globodera pallida) without (1991) or with accompanying drought (1992) influenced the rooting dynamics of potatoes. The main effec t of potato cyst nematodes in 1991 was a retarded root length. At a depth o f 10 cm and without nematodes, the maximum total root length was produced 6 0 days after planting. At a depth of 45 cm, this point was reached after 80 days. With nematodes (2.5, 10 and 40 living larvae per gram of soil), howe ver, the date at which maximum root length was produced was retarded with a t least 20 days, depending on the infestation level of the soil. At a depth of 45 cm, nematodes at the highest infestation level also eventually resul ted in a shorter root length. At a depth of 10 cm, nematodes resulted in a somewhat greater root length. The effects of nematodes on the longevity of potato roots were analysed by following the fate of individual root segment s. It was concluded that in the first experiment (1991), the rate at which roots decayed was higher without nematodes than with nematodes. Combining t he data for root length production with root length decay, it was found tha t without nematodes, the standing living root length was only higher in the first part of the season. Also, from the second experiment (in 1992), in w hich the effect of nematodes was studied in combination with drought, potat o roots did not show a reduced longevity with nematodes. The yield of potat oes in the presence of nematodes is discussed. (C) 1998 Elsevier Science B. V. All rights reserved.