New Zealand Journal of Agricultural Research abstracts
Microbial pathogens and plant parasitic nematodes in pastures with declining
vigour
S. U. SARATHCHANDRA
R. N. WATSON
R. A. SKIPP
G. BURCH
J. A. BROWN
N. R. COX
AgResearch
Ruakura Agricultural Research Centre
Private Bag 3123
Hamilton, New Zealand
Abstract Two years after establishment, areas of low vigour
(LV) were noticed within a white clover (Trifolium repens)/ryegrass
(Lolium perenne) pasture. These areas became progressively larger, and,
two years later, the pasture had low vigour, comprising only 3% white clover.
Clover tissue nitrogen and phosphorus levels were greater in high vigour (HV)
than in LV herbage. There were no differences (P > 0.05) in "total"
bacteria, fluorescent pseudomonads, or proportions of deleterious bacteria in
LV and HV white clover roots (mean log10 CFUs for total count and fluorescent
pseudomonads were 9.4 and 8.8, respectively, and the proportions of deleterious
bacteria encountered in these groups were 6.9% and 17.5%). There was a 9-fold
difference (P < 0.01) in the white clover dry matter between LV areas
and HV areas in February, increasing to 25-fold (P < 0.01) in March.
The total dry matter yield differences, which included grasses and clover, were
2.7- and 2-fold (P < 0.01) for the two months. More fungi were
isolated (P < 0.05) from LV white clover roots than from HV roots
(164 and 104 isolates, respectively). This was mostly due to greater numbers
(P < 0.01) of Codinaea fertilis in LV roots (111 cf.
41 in HV). In ryegrass roots, there were also greater numbers
(P < 0.01) of total fungi in LV roots (97 cf. 50 total
isolates in HV), mostly due to higher populations of Fusarium oxysporum
in LV roots (29 isolates cf. 5 in HV). There was no difference
(P > 0.05) in the Soil Pathogenicity Index between LV and
HV soil. The plant parasitic nematode populations in 250 ml of soil in LV and
HV areas were 42.7 and 9.7 for Heterodera and 28.1 and 3.9 for
Meloidogyne, respectively.
Keywords Codinaea fertilis; clover vigour;
Trifolium repens; root fungi
New Zealand Journal of Agricultural Research, 2000, Vol. 43: 549-558
0028-8233/00/4304-0459 $7.00/0 (c) The Royal Society of New Zealand
2000
PDF file of entire paper: medium quality (782K); (scanned from paper original: notes about this process)
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