Density-dependent growth response and sensitivity of Meloidogyne incognita to Maerua angolensis and Tabernaemontana elegans: Card model

Abstract

Curve-fitting Allelochemical Response Dosage (CARD) computer-based model has proven to be a valuable tool in the definition of dosage response relationships between organisms and various plant extracts. Its use in the explanation of the relationship between Maerua angolensis and Tabernaemontana elegans concentrations and Meloidogyne incognita second-stage juvenile (J2) hatch and mortality has not been reported. The objective of this study was to use the CARD model in the determination of M. incognita sensitivity, density-dependent growth (DDG) patterns and minimum inhibition concentrations of M. angolensis and T. elegans plant extracts on juvenile hatch and mortality. The CARD model quantified concentration ranges of the two plant extracts that could stimulate (Dm − Rh), saturate (Rh − D0) and inhibit (D0 − D100), J2 hatch and mortality. Meloidogyne incognita J2 hatch was moderately sensitive to M. angolensis and T. elegans plant extracts with average sensitivity ranking of 20 and 19 units, respectively. J2 mortalities were moderately sensitive to T. elegans average sensitivity ranking of 15 units, whereas highly sensitive to M. angolensis at 2 units. The minimum juvenile hatch inhibition and lethal concentrations for the two extracts were comparable and very low at 0.07, 0.06 and 0.13, 094 mg mL−1, respectively. In conclusion, the low minimum concentrations for M. incognita J2 hatch inhibition and lethal concentrations of M. angolensis and T. elegans plant extracts and moderate sensitivity values provide substantial evidence of high potency of the two extracts in the potential management of M. incognita