DYNAMICS OF SOIL NEMATODE COMMUNITIES IN TOMATO CROPS FROM A PRODUCTIVE REGION OF ARGENTINA

SALAS, AUGUSTO; ACHINELLY, MARÍA FERNANDA

NEMATROPICA

ORGANIZATION TROP AMER NEMATOLOGISTS

Lugar: Florida; Año: 2018 vol. 48

0099-5444

The objective of this work was to evaluatenematode communities through ecologicalindexes to determine those variables that are thebest indicators of changes in soils subjected totomato crops under two different agriculturalmanagement systems, in La Plata, Buenos Airesprovince, the main tomato producing region ofArgentina. A seasonal crop and an intensiveconventional crop with use of agrochemicals wereconsidered for the study. Site A was characterizedby tomato crops during spring and summer seasonand covered by weeds the rest of the year, usingorganic fertilizers as the only external income.Site B was represented by an intensiveconventional culture with methyl bromide andAgrocelhone application as nematicide before theseedtime the first year and towards the end of thesecond year of sampling respectively. Soilsamples were collected between September 2015and October 2017. At each site, a single sample,totaling a minimum volume of 500 cm3, wascollected; this comprised multiple soil cores (c.20), taken to a depth of 20 cm using a steel auger(4-cm diameter). A total of nine samples weretaken for each site. In lab the technique ofcentrifugation was performed for nematodeisolation. The determination at the genus level andthe count of nematodes was carried out to obtainthe values of abundance per site. To identifychanges in the structure of the nematodecommunity, diversity and function indexes wereanalyzed and tested to search differences betweensites. Following multivariate analysis wereconsidered: ANOSIM to determine significantdifferences between sites, SIMPER to estimate thecontribution of each taxon to average Bray Curtisdissimilarity and MDS to model the proximity(similarity) between the samples. The resultsshowed significant differences between Richness(= N0), abundance, Margalef (d) and Σ MI, nodifferences being observed in MI, Shannon-Wiener, Pielou and other diversity indicesanalyzed. Significant differences were foundbetween the sites using the ANOSIM test (globalR= 0.5, p value=0.002). SIMPER analysisindicated that Helicotylenchus, Filenchus, and theopportunistic enrichment nematode Rhabditiswere mainly responsible for the dissimilaritybetween sites. The MDS indicated evidentseparation of samples taken after the applicationof methyl bromide and Agrocelhone. ∑MIshowed changes in the community structure ofsoil nematodes. This could be related to theinclusion of plant-feeding nematodes in thisindex. Similar values for MI between sites couldbe related to the abundance of bacteriophagenematodes due to enrichment of the environmentwith organic fertilizers (Site A) and disturbancefor fumigants (Site B). As results of this work, wepresent the most sensible variables in nematodecommunities, in soils under horticulturalmanagement in the city La Plata. The lack ofstudies in this region encourages to keep on thistype of analysis to estimate changes in thediversity of nematofauna as measure of ecologicalquality for these agricultural soils.