Survival of root-lesion nematode Pratylenchus neglectus during progressive soil desiccation after growth of wheat in a vertisol

Abstract

Whether soil desiccation causes a fall in peak population abundances of Pratylenchus neglectus after wheat growth was investigated by drying a vertisol through a range of moisture contents (MC) by both fast and slow drying methods. Live nematodes were then extracted for 2 and 7 days and counted in four life stages (adult and juvenile stages J2, J3 and J4). The population of P. neglectus declined more steeply with decreasing soil moisture content from fast drying than from slow drying. These trends were modelled by regression equations. Upon desiccation of the soil from an initial 64.4% MC to the plant permanent wilting point (31.5% MC), 48% of the nematodes survived after fast drying, but 86% survived after slow drying. With further desiccation to 21% MC only 23% of the P. neglectus population survived after fast drying, whereas 81% of the population survived after slow drying. On continued drying, the fast dried soil was at 11.9% MC after 7 days with virtually no surviving P. neglectus, whereas the slowly dried soil reached 16.5% MC after 8 days with 79% surviving. The P. neglectus population declined by 2.2 and 0.5% per 1% loss of soil moisture for fast and slow drying, respectively. With fast drying, all life stages declined; however, with slow drying, only the J2 stage declined with 44% surviving at 16.5% MC. This information can be applied to crop growth modelling, to extraction techniques for soil from the glasshouse and field, and to consideration of whether molecular methods measure DNA from recently dead nematodes killed by soil desiccation in the field giving an overestimation of the number of live nematodes.