Nondestructive Evaluation of Cotton Genotypes for Resistance to Reniform Nematode

Identification of new sources of reniform nematode (Rotylenchulus reniformis Linford and Oliveira) resistance in cotton is critical to expanding host plant resistance to manage this important pathogen. Phenotyping plants in early breeding generations without destructive sampling would be useful for introgression of nematode resistance from exotic germplasm resources; therefore, a rapid, nondestructive method was developed to assess host plant resistance to the reniform nematode based on the number of females infecting the roots. In one set of experiments, the root system was cut off at 0, 1, 2.5, or 5 cm below the soil line and used to assess the number of females infecting this portion of the root system. Resistance could be accurately determined while leaving up to 5 cm of roots with the shoot. In a second set of experiments, the rate of plant recovery and reproductive development was evaluated using a combination of root retention (0, 1, 2.5 cm, or all root) and shoot retention (leaves at top two nodes, leaves at bottom two nodes, no leaves, all leaves) treatments. Plants more rapidly recovered using a treatment combination in which the top leaves and 2.5 cm roots were kept. This combination performed similarly to plants with neither shoots nor roots modified and was harvested 20 days sooner compared to some other treatment combinations.