Proof-of-concept for managing Meloidogyne hapla parasitic variability in carrot production soils

Abstract

Without resistant cultivars, conducive cropping systems and heterogeneous soils, managing parasitic variability of Meloidogyne hapla is a major challenge in carrot production. In glasshouse studies we tested a hypothesis that knowledge of carrot cultivars’ degrees of host suitability to populations of M. hapla could lead to developing site-specific management strategies. ‘Site-specific’ encompasses production practices, soil conditions and nematode problems. Interactions between the carrot cvs Abledo, Abundance, Enterprise, Eufora, Prodigy, Recoleta and Sugar Snax, and four M. hapla populations, Mh 1, Mh 2, Mh 3 and Mh 4, were examined. The tomato cv. Rutgers, in which the populations were cultured, was used as a nematode viability control. The first three populations were isolated from mineral soils and the fourth one from organic (muck) soil, all soils typical of carrot and other vegetable production in the US Midwest. While the reactions varied by population and by cultivar, the carrot cultivars proved to be hosts as suitable as, or more suitable than, cv. Rutgers tomato. All of the carrot cultivars were hosts as suitable as cv. Rutgers tomato to Mh 2, all but cv. Sugar Snax to Mh 3 and all but cvs Sugar Snax and Abundance to Mh 1. However, the Mh 3 infection levels in cv. Sugar Snax were as high as the Mh 2 infection levels. The cvs Sugar Snax and Abundance were the least suitable hosts for Mh 4 and Mh 1, and cv. Prodigy for Mh 4. The results suggest that identifying the reproductive potential of a resident M. hapla population is critical to making decisions about what carrot cultivars to plant as well as to minimise inoculum build-up in an infested field. The implications of the results across rotation crops are discussed.