Nematode communities differ in Hopi landrace maize and commercial maize

Selection pressures of crop breeding in varying abiotic contexts may produce cultivars differing in their relationships with belowground organisms. Nematode assemblages associated with a Hopi maize (Zea mays L.) landrace and two commercial maize varieties were examined at three traditional farms (two irrigated, one dry-farmed) near the village of Moenkopi on the Hopi Reservation in Arizona, U.S.A. At each farm, the landrace and one commercial maize variety were cultivated in close proximity. Within the two irrigated farms, densities of free-living nematodes, but not plant parasitic nematodes, were higher in landrace plots compared to commercial variety plots; however, at the dry-farmed site the nematode assemblages associated with the two maize varieties did not differ. Nonmetric multidimensional scaling (NMDS) and multiple response permutation procedure (MRPP) showed that at the irrigated farms, nematode assemblages associated with landrace maize differed significantly from those associated with commercial maize in analyses based on functional guilds, feeding groups and non-phytoparasitic c-p groups. Assemblages at the dry-farmed site were different from those at the irrigated sites in community composition based on morphotypes, functional guilds, and feeding groups, but were similar to the irrigated commercial variety plots based on c-p groups. Nematode abundances were likely constrained by water availability at the dry-farmed site, but at the irrigated sites, nematode community dissimilarities between the landrace and the commercial maize variety may have resulted from differences in plant-soil microbe interactions for the two crop varieties. Selection pressures associated with Hopi agroecosystems might have produced landraces with different belowground allocation strategies than commercial crop varieties selected under high resource conditions.