Abstract
Growing gladiolus corms in soil-less culture fertilized by soluble nutrients raised the question of how both Trichoderma harzianum and Aneurinobacillus migulanus enhance plant growth and provide protection against infection by Fusarium oxysporum f. sp. gladioli. Changes in the concentrations of the plant growth regulators (PGRs) gibberellic acid (GA3), indole acetic acid (IAA) and abscisic acid (ABA) were determined in gladiolus corms following treatment with T. harzianum, A. migulanus and F. oxysporum f.sp. gladioli. The presence of these PGRs in corms was confirmed using liquid chromatography-mass spectrometry (LC-MS/MS) and the compounds quantified using high performance liquid chromatography (HPLC). Concentrations of both GA3 and IAA increased linearly in all corms over the 10 days after treatments; lowest concentrations of both PGRs were consistently found in corms inoculated with F. oxysporum f. sp. gladioli. In contrast, highest concentrations of both GA3 and IAA occurred in corms treated with T. harzianum alone. Highest concentrations of ABA, however, were found in corms inoculated with F. oxysporum f. sp. gladioli, regardless of the presence of T. harzianum or A. migulanus. Treatments with T. harzianum or A. migulanus in the absence of F. oxysporum f.sp. gladioli maintained ABA concentrations at the same levels as control corms. These results indicate that promotion of Gladiolus growth by T. harzianum or A. migulanus may be partly mediated through stimulation of the production of GA3 and IAA in corm tissues. Increases in these PGRs may also be a mediator in the biological control activity shown by T. harzianum or A. migulanus.
Highlights
Plant growth regulators (PGRs) are organic compounds naturally occurring in plants, which regulate many processes in plant development
Between days 2 and 8, Gibberellic acid3 (GA3) concentrations in corms treated with T.harzianum or A. migulanus, followed by inoculation with F. oxysporum f. sp. gladioli were significantly higher than in corms treated with F. oxysporum f. sp. gladioli alone, or in control corms (P< 0.001)
The GA3 concentrations in corms treated with A. migulanus followed by inoculation with F. oxysporum f. sp. gladioli, were significantly lower than in those inoculated with A. migulanus alone (P>0.05)
Summary
Plant growth regulators (PGRs) are organic compounds naturally occurring in plants, which regulate many processes in plant development. The combination between T. harzianum and A. migulanus was prepared by mixing the same volume of suspension of antagonist in beaker, immersing surface sterilized corms in the mixed suspension for 30 min and inoculating with the pathogen, as described above. Between days 2 and 8, GA3 concentrations in corms treated with T.harzianum or A. migulanus, followed by inoculation with F. oxysporum f.
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