Influence of the nematodesHeterodera trifoliiandMeloidogyne haplaon nitrogen fixation by white clover under glasshouse conditions

Abstract

The growth and N content of rhizobia-inoculated white clover growing in soils fumigated with methyl bromide and mixed with fertiliser were measured. Treatments comprised nematode-free controls, and inoculation with Heterodera trijolii cysts, for Kokotau silt loam, and with H. trijolii cysts, Meloidogyne hapla larvae, and with both nematodes together, for Egmont brown loam; two P levels were added to each soil. N mineralisation in soil similarly treated, but without growing plants, was also determined. In Egmont soil, but not in Kokotau, herbage dry mater yields and plant N were sometimes greater at the higher level of added P. Level of added P had no effect in either soil, at the end of the trial, on fresh weight of roots, number of rhizobia nodules, or numbers of H. triiolii, when present; numbers of M. hapla in Egmont soil were greater at the higher P level. All nematode treatments eventually reduced dry matter yields, plant N%, and plant N yields: in Egmont soil H. triiolii had more effect than M. hapla, and their effects when inoculated toegther were no greater than those of H. triiolii alone. At the final harvest, root weight was significantly lower in all nematode treatments, and numbers of rhizobia nodules were generally less; within nematode-infested pots numbers of nodules and nematodes were positively, and usually significantly, correlated. Fumigated soils incubated without plants produced appreciable amounts of mineral-N, mainly ammonium-N, initially more than produced by non-fumigated soil; appreciable nitrate-N was roduced only in Egmont soil inoculated with H. trijolii and the associated soil organic fragments. Amounts of N that could have been fixed by the clovers were estimated by using the soil N mineralisation data and the plant N data: they averaged 0.424 g and 0.294 g N per pot for control plants, and 0.247 g and 0.046 g N per pot for nematode-infested plants, in Kokotau and Egmont soils respectively. These nematodes can adversely affect the N-fixing capacity of white clover, and their effect should be assessed in the field, but the results do not clearly indicate the mechanism (s) responsible.401

Parasitism effects on white clover by root-knot and cyst nematodes and molecular separation of Heterodera daverti from H. trifolii

“…Persistence of white clover was also reduced from 12 to 20 % when infected by M. incognita (Pederson et al 1991). Finally, parasitism by root-knot nematodes differentially affected white clover nutrition reducing total N from 27 to 60 % by M. javanica or from 43 to 48 % by M. hapla infections, although the mechanism by which these nematodes affects N fixation has not been determined (Yeates et al 1977;Mercer 1994). Similarly, differential pathogenicity has been documented by the parasitism with cyst nematodes.…”

Pasture renewal on Bay of Plenty and Waikato dairy farms: impacts on pasture performance post-establishment

“…The increased abundance of clover-feeding cyst nematodes in renewed pastures was also likely to be in response to increases in clover content after renewal (Bell et al 2009). In turn, the damage these nematodes do to clover roots would subsequently reduce clover growth and nitrogen fixation (Yeates et al 1977;Yeates 1978). Of the root knot nematode species identified, two (Meloidogyne hapla Chitwood and M. trifoliophila) were most likely feeding on the white clover component of the pasture whereas M. fallax is capable of feeding on both clover and grass components of pasture.…”

Suppression of plant parasitic nematodes in pastoral soils amended with chitin

“…The major root-parasitic nematodes causing significant damage in New Zealand pastures are the sedentary endoparasites Heterodera trifolii (clover cyst nematode) and Meloidogyne spp. (rootknot nematodes) (Yeates et al 1977;Watson et al 1985). The migratory endoparasites Pratylenchus spp.…”