Abstract
To be effective, biocontrol agents, fungi need to colonize roots under a wide range of conditions. The ability do so is called rhizosphere competence. A common beneficial fungus, Trichoderma harzianum, has been bred to produce a new strain, T-22, that has exceptionally high rhizosphere competence. In field experiments, we have demonstrated that T-22 was resistant to edaphic conditions that reduce colonization by indigenous Trichoderma species, so that it can provide protection against root pathogens. Well-drained sand, stone or gravel soils supported lower populations of wild Trichoderma than did loams (10 0.5 vs 10 3.3 cfu/g), but populations of T-22 were high in all soils (>10 4 cfu/g). In a multivariate analysis of soil characteristics affecting colonization, only soils with low Ca and low pH had reduced populations. No other measured soil characteristics were correlated with colonization. When sown in the field at different initial soil temperatures ranging from 10 to 27 °C, T-22 populations were unaffected by temperature, having a population from 10 4.6 to 10 5.4 cfu/g. Indigenous strains were 10 3 in cold soils, peaked at 10 4 at 15 °C, declining in later sowings due to higher biological competition. Differences in microbial competition had little effect. Roots were equally colonized in the differing soil microflora in three management systems at the Rodale Farming Systems Trial. Invading an existing soil microbial community is the most difficult thing to achieve with a biocontrol organism. These data show that T-22 is the first to consistently do so.
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Claims 8
Claim · model-written summary
T-22 maintained root colonization under soil conditions that reduced indigenous Trichoderma.
Verbatim
e0“T-22 was resistant to edaphic conditions that reduce colonization by indigenous Trichoderma species”
t0“Sweet Corn”
Claim · model-written summary
Wild Trichoderma populations were lower in well-drained sand, stone or gravel than in loam.
Verbatim
e0“Well-drained sand, stone or gravel soils supported lower populations of wild Trichoderma than did loams (10 0.5 vs 10 3.3 cfu/g)”
t0“Sweet Corn”
Claim · model-written summary
T-22 populations exceeded 10 4 cfu/g across soils.
Verbatim
e0“populations of T-22 were high in all soils (>10 4 cfu/g)”
t0“Sweet Corn”
Claim · model-written summary
Low calcium and low pH soils had reduced colonizing populations.
Verbatim
e0“only soils with low Ca and low pH had reduced populations”
t0“Sweet Corn”
Claim · model-written summary
Other measured soil characteristics were not correlated with colonization.
Not reportedDirection
Verbatim
e0“No other measured soil characteristics were correlated with colonization”
t0“Sweet Corn”
Claim · model-written summary
T-22 populations were unaffected by 10 to 27 °C initial soil temperature.
Verbatim
e0“When sown in the field at different initial soil temperatures ranging from 10 to 27 °C, T-22 populations were unaffected by temperature, having a population from 10 4.6 to 10 5.4 cfu/g”
t0“Sweet Corn”
Claim · model-written summary
Indigenous strain populations peaked at 15 °C and declined in later sowings.
Verbatim
e0“Indigenous strains were 10 3 in cold soils, peaked at 10 4 at 15 °C, declining in later sowings due to higher biological competition”
t0“Sweet Corn”
Claim · model-written summary
Different soil microflora in three management systems had little effect on root colonization.
Verbatim
e0“Differences in microbial competition had little effect. Roots were equally colonized in the differing soil microflora in three management systems at the Rodale Farming Systems Trial”
t0“Sweet Corn”