Damage Potential and Reproduction of Meloidogyne incognita Race 3 and M. arenaria Race 1 on Kenaf.

The effects of Meloidogyne incognita race 3 and M. arenaria race 1 on growth of kenaf cv. Everglades 41 was determined under greenhouse conditions. Seedlings of kenaf were inoculated with initial population densities (Pi) of 0, 625, 1,250, 2,500, 5,000, and 10,000 eggs/plant and placed on greenhouse benches in a randomized complete block design. Plant growth and nematode reproduction were assessed 6 and 12 weeks after inoculation. Growth suppression of kenaf in response to increasing Pi was observed 6 weeks after inoculation. Severe damage was observed by all Pi levels of M. incognita and M. arenaria at 12 weeks after inoculation. Plant height, basal stem diameter, and fresh and dry shoot weights had a negative linear relationship to log(Pi + 1) for both M. incognita and M. arenaria. Plant height was reduced 25%, basal stem diameter was reduced 19%, and dry shoot weights were reduced 64% at the highest inoculum rates of M. incognita. Similar reductions were observed for M. arenaria. Greater levels of root necrosis were observed with M. incognita than M. arenaria at similar inoculum levels. High reproductive factors (Rf) were observed on kenaf for both M. incognita (48 - 1,804) and M. arenaria (257 - 4,240), with the highest Rf values occurring at the lowest Pi. The host status of kenaf renders it unsuitable for use in rotation systems with other susceptible crops.