COMPARATIVE HOST SUITABILITY OF SELECTED CROP SPECIES TO TYLENCHORHYNCHUS-ZAMBIENSIS

The host suitability of five genotypes of maize (Zea mays), alfalfa (M edicago saliva cv. Cimarron), red clover (Trifolium pratense cv. Mammo th), soybean (Glycine max cv. Bragg), sunflower (Helianthus annus cv. CCA82-2), wheat (Triticum aestivum cv. Pioneer 2508), and white clover (Trifolium repens cv. Dutch White) to Tylenchorhynchus zambiensis wer e evaluated in two greenhouse experiments. Plants were inoculated with 5000 nematodes, and populations and effects on growth were determined 60 days later. The host status was determined by calculating a reprod uctive factor (R) where R = final population (Pf)/initial population ( Pi) and where R less than or equal to 1 = nonhost; R = 1.1-4 = poor ho st; R = 4.1-10 = fair host; R = 10.1-20 = good host; and R > 20 = exce llent host. Maize genotypes 'MO17 x A634', 'MM603', 'ZM-1760', 'TGR 13 49', and 'Natal 8-Row Flint' were excellent hosts for T. zambiensis. A lthough plant growth was minimally affected by T. zambiensis, highest numbers of nematodes per gram of dry root weight were recovered from ` MO17 x A634'. The maize genotype 'TGR1349' was the most susceptible of the maize genotypes evaluated, exhibiting a significant reduction in plant growth. DIY root weights in all the maize genotypes were higher in noninoculated controls compared to inoculated treatments. Wheat was a good host for T. zambiensis, but plant growth was not affected by t he nematode. Alfalfa, red clover, and white clover were poor hosts for T. zambiensis. Soybean was a poor host in the first experiment but wa s a fair host in the second test. Sunflower was a nonhost.