Can Agricultural Practices in Strawberry Fields Induce Plant-Nematode Interaction towards Meloidogyne-Suppressive Soils?

Abstract

The importance of benign approaches to manage the root-knot nematodes (RKNs, Meloidogyne spp.) in strawberry farms has become more evident with increasing strawberry production and export in Egypt. Therefore, data accumulated on biosolarization and soil amendments to favor beneficial microorganisms and maximize their impact on RKN management are built on a robust historical research foundation and should be exploited. We examined RKN population levels/parameters in three strawberry export governorates, six farms per governorate, to characterize the exact production practices that are responsible for RKN-suppressive soils. All selected farms enjoyed soil biodisinfestation resulting from incorporating organic amendments followed by a plastic cover to suppress soil pathogens. Various safe and inexpensive agricultural practices in the El-Ismailia and El-Beheira governorates were compared to the toxic and expensive fumigants that could eliminate RKNs in the Al-Qalyubia governorate. Two farms at El-Ismailia were of special interest as they ultimately showed almost zero counts of RKNs. The two farms were characterized by incorporating cow manure [containing 0.65% total nitrogen, 21.2 carbon to nitrogen (C/N) ratio] and poultry manure (0.72% total nitrogen, 20.1 C/N ratio) followed by soil solarization via transparent, 80-µm thick plastic covers for 60−65 summer days as pre-strawberry cultivation practices, and similar covers were used after transplanting. Typically, the longer the pre-plant soil solarization period with thicker transparent plastic covers, the better it could suppress the RKN population densities in the tested farms. Their soils were characterized by relatively high pH and low electrical conductivity. The significant development in biocontrol genera/species abundance and frequency could explain the lower (p < 0.0001) RKN population levels inhabiting the farms of El-Ismailia than the El-Beheira governorate. These factors could provide the first approximation of key practices and factors that could collectively contribute to distinguishing and exploiting soil suppressiveness against RKNs. We discussed edaphic properties and production practices that could modulate populations of natural RKN antagonists for sustainable strawberry cultivation.

Keywords: Meloidogyne; biocontrol; soil microorganisms; strawberry; suppressive soil.

Figure 1

Relative mobility rate (Rm) of esterase isozymes identified from individual root-knot nematode females (♀ and eggs (E) following electrophoresis on polyacrylamide gel. Prevalent esterase phenotypes considered to be specific for M. javanica are located at the middle of 40 and 50 Rm for the females.

Figure 2

Principal component analysis biplot of first and second principal components of the fungal descriptive profiles in rhizospheres of strawberry in El-Ismailia farms. Farms are shown in red, while fungal groups/species found after 3 and 5 months of transplanting are shown in blue.

Figure 3

Principal component analysis biplot of first and second principal components of the fungal descriptive profiles in rhizospheres of strawberry in El-Beheira farms. Farms are shown in red, while fungal groups/species found after 3 and 5 months of transplanting are shown in blue.