Nematode abundance and diversity in sugarcane fields in Brazil

Abstract

Edaphic climatic conditions directly affect the population dynamics of nematode assemblages and management strategies. The objective of this study was to characterize spatiotemporal changes in nematode abundance and diversity in sugarcane fields of northeastern Brazil under different edaphic climatic conditions. Soil samples from seven geoenvironmental sites under continuous cultivation were taken at planting and 4, 9, and 14 months after planting. Nematode abundance and diversity varied with the soil's physical and chemical characteristics. Sites in the rainfed and irrigated coastal tables as well the floodplain had higher number of nematodes in contrast to the flat-land and hillside. The abundance of plant-parasitic nematodes increased concurrently with crop development, but the number of taxa decreased. Meloidogyne and Pratylenchus were the dominant plant-parasitic genera across locations, but bacterivores were dominant in southern sites at field replanting. Heat map delineated two distinct groups of nematode distribution within the geoenvironmental zones, rather than the sampling times. Pratylenchus density was high in both groups, but in contrast with Meloidogyne and Criconemella, the abundance of Pratylenchus and Helicotylenchus was higher in sites with lower soil bulk density and higher porosity, clay, organic matter, and water contents as those in the southern sites, reflecting edaphic climatic conditions.

Responses of nematode abundances to increased and reduced rainfall under field conditions: A meta‐analysis

“…It was generally expected that rainfall would have positive impacts on both above‐ and belowground fauna, particularly in water‐limited systems. Surprisingly, total and trophic group's abundances showed no response to increased rainfall across all studies, with individual studies ranging from negative (e.g., Feng et al, 2016; Maranhão et al, 2018) to neutral (e.g., Papatheodorou et al, 2012) and positive (e.g., Andriuzzi et al, 2018; Cesarz et al, 2017) effects. However, it appears that the benefit of increased rainfall may take longer to manifest given the higher total abundances and more plant parasitic nematodes observed in the longer term experiments only.…”

“…Specifically, reduced rainfall has immediate impacts on nematode abundances, whereas increased rainfall takes longer to manifest, with correlations not statistically significant across short‐term studies (<1 year). Hence, it may be impractical to reach conclusions about the effects of increased rainfall on soil biota in short experiments (Freckman et al, 1987; Maranhão et al, 2018). However, as discussed above, in the longer term, enhanced resource availability will likely result in increased nematode numbers and shifts in community composition.…”

“…Similarly, an increase in feeding activities of microbial grazers could suppress microbial biomass and activity, resulting in weaker responses to increased rainfall (Nielsen, 2019). Furthermore, an increase in predators may cause a decrease in overall nematode abundance (Freckman et al, 1987; Maranhão et al, 2018). Our results hence suggest that climate change may result in altered soil food web composition given observed trophic‐group‐specific responses.…”

Morphological and Morphometric Characterization of Pratylenchus Species in Sugarcane Cropping Areas of Pernambuco State

“…The damage caused by nematodes varies according to the population level, soil type, and crop variety (SILVA et al, 2016;BELLÉ et al, 2017;NORONHA et al, 2017;MARANHÃO et al, 2018). When at a high population density, nematodes cause severe damage to the root system, which becomes underdeveloped and inefficient, leading to decreased productivities (SILVA et al, 2017;PORTO et al, 2018).…”

Survey of nematodes associated with sugarcane in the state of Paraná, Brazil

“…considered economically important pathogens (MARANHÃO et al, 2018), Aphelenchus, Mesocriconema, Tylenchorhynchus, Trichodorus, Hoplolaimus, Tylenchus, and Ditylenchus, when at high population levels, can severely interfere with plant development (SHOWLER et al, 1990;BOND et al, 2000).…”