Nematode Susceptibility Rankings From Soft-Tissue X-Ray Imaging

Eight lines of cotton plants from the Auburn University reniform nematode resistance breeding program were grown under greenhouse conditions at the University of Tennessee in soil from infested cotton fields from West Tennessee.  Four of the lines were known to be susceptible and four were known to be resistant.  The plants were planted in containers with 500 cc of soil with 1,500 nematodes per 100 cc of soil.  The plants were grown for six weeks.  The plants were excavated with their roots carefully washed, preserving egg masses and embedded females.  They were then subjected to X-ray imaging and evaluated with digital imaging software.  Egg masses were counted and their locations on the root system were documented.  The overall root system of each plant was characterized to determine the root system architecture of the infected plants.  Mean egg mass counts were divided by the mean values of total root length of the different lines to get a normalized measure of susceptibility.   These measures of “quantified susceptibility” were then compared to the results of traditional susceptibility determination methods used in the field.