Screening Trifolium spp. for Response to Meloidogyne spp.1

Abstract

Lack of a rapid, reliable screening procedure has hampered the identification and development of clover (Trifolium spp.) germplasm with tolerance to Meloidogyne spp. The objectives of this research were: (i) to evaluate a previously developed Meloidogyne screening technique for use on Trifolium spp., (ii) to evaluate the effects of growth container sizes and nematode inoculum rates on gall scores, and (iii) to compare the relative levels of susceptibility of several Trifolium spp. to Meloidogyne spp. In Exp. 1, one line each of crimson (Trifolium incarnatum L.), red (T. pratense L.), white (T. repens L.), and arrowleaf (T. vesiculosum Savi.) clover was grown in either 50 or 150 cm3 Conetainers®, infested with either 0, 1, 3, or 9 eggs cm−3 soil of one of three Meloidogyne spp. and scored for severity of galling 10 weeks after infestation. In Exp. 2 and 3, germplasm lines of white and crimson clover, T. mutabile Portenschl., and 'Fresa' strawberry clover (T. fragiferum L.) were evaluated for response to infestation with 9 or 10 Meloidogyne spp. eggs cm−3 soil when grown in 150 cm31 Cone‐tainers. The 150 cm3 Cone‐tainers provided a less dense plant spacing and were easier to maintain at uniform soil moisture among cones than the 50 cm3. Gall scores were usually lower on plants grown in 50 cm3 Cone‐tainers than in the 150 cm3 size, thus only the 150 cm3 size was used in later experiments. In the 150 cm3 Cone‐tainers, the 9 eggs cm −3 soil infestation rate gave higher (P < 0.001) gall scores than the lower rates for all legumes except arrowleaf clover. Overall tolerance to Meloidogyne spp. was crimson, > red = white > arrowleaf clover. Only one white clover clone, which traces to SCI germplasm, had a high level of tolerance to M. incognita (Kofoid and White, 1919) Chitwood, 1949. Fresa strawberry clover and one introduction of T. mutabile were highly susceptible to the three Meloidogyne spp. Variation in gall scores among 31 lines of crimson clover was significant and lines were identified with lower gall scores than ‘Dixie’.