The Structure of Rhizosphere Fungal Communities of Wild and Domesticated Rice: Changes in Diversity and Co-occurrence Patterns

The rhizosphere fungal community affects the ability of crops to acquire nutrients and their susceptibility to pathogen invasion. However, the effects of rice domestication on the diversity and interactions of rhizosphere fungal community still remain largely unknown. Here, internal transcribed spacer amplicon sequencing was used to systematically analyze the structure of rhizosphere fungal communities of wild and domesticated rice. The results showed that domestication increased the alpha diversity indices of the rice rhizosphere fungal community. The changes of alpha diversity index may be associated with the enrichment of Acremonium, Lecythophora, and other specific rare taxa in the rhizosphere of domesticated rice. The co-occurrence network showed that the complexity of wild rice rhizosphere fungal community was higher than that of the domesticated rice rhizosphere fungal community. Arbuscular mycorrhizal fungi (AMF) and soilborne fungi were positively and negatively correlated with more fungi in the wild rice rhizosphere, respectively. For restructuring the rhizomicrobial community of domesticated crops, we hypothesize that microbes that hold positive connections with AMF and negative connections with soilborne fungi can be used as potential sources for bio-inoculation. Our findings provide a scientific basis for reshaping the structure of rhizomicrobial community and furthermore create potential for novel intelligent and sustainable agricultural solutions.

Diversity of Soil Filamentous Fungi Influenced by Marine Environment in São Luís, Maranhão, Brazil

Introduction. In recent decades, there has been an intensification of environmental problems, which are becoming increasingly critical and frequent due to population growth. Microorganisms, including soilborne fungi, play an essential role in maintaining and balancing the environment. One of the most impacted ecosystems in São Luís, Maranhão, Brazil, is the Jansen Lagoon State Park, an important tourist spot, which has suffered anthropogenic actions such as the dumping of household waste (sewage) in its body of water. As a consequence, these pollutants can accumulate in the adjacent soil, since the body of water is near this substrate. The objectives were to isolate and identify filamentous fungi from the soil of the Jansen Lagoon State Park. Methods. Monthly soil samples were collected and later processed using the modified suspension technique according to Clark (1965). Results. The isolated genera were Aspergillus, Penicillium, Trichoderma, Absidia, and Fusarium. Aspergillus is the fungal genus of greater dominance in the soil of the Jansen Lagoon State Park. Aspergillus niger was the dominant species (37%), followed by A. tamarii (21.6%). Conclusion. The main isolated fungi from the Jansen Lagoon State Park were Aspergillus niger and Aspergillus tamrii. These fungi can be used as biological markers of pollution and as biodegraders and/or bioremediators to improve the area studied.

Optimizing Fungicide Inputs for Management of Lettuce Drop Caused by Sclerotinia minor and S. sclerotiorum

Lettuce drop, caused by the soilborne fungi Sclerotinia minor and S. sclerotiorum, continues to be an important disease on this crop in Arizona. Trials were conducted over a 5-year period to compare different fungicides as well as the number, timing, and method of application. Compared with nontreated plots, disease reduction ranging from 49.6 to 61.0% was achieved on lettuce beds containing S. minor and treated with fluopyram + trifloxystrobin, fluazinam, fluxapyroxad + pyraclostrobin, and boscalid. Treatment of beds containing S. sclerotiorum with Coniothyrium minitans, iprodione, and boscalid reduced lettuce drop from 50.6 to 71.5%. No difference in disease control was noted between one and two applications of boscalid in plots containing either pathogen. In the presence of S. minor, beginning the first of two applications of boscalid after seeding did not differ from starting after thinning; however, in plots containing S. sclerotiorum, starting application after seeding was superior to beginning after thinning. Physical incorporation of soil treated with boscalid to a depth of 5.0 cm did not differ from soil treatment without incorporation in plots containing S. minor or S. sclerotiorum. On the other hand, in beds containing S. sclerotiorum, incorporation of soil treated with iprodione improved disease control compared with no incorporation.

Response of soil fungi and biological processes to crop residues in no-tillage system

ABSTRACT Soil management and crop rotation can directly affect the soil microbial community. This study aimed at determining soil quality indicators and soilborne fungi in a no-tillage system. A randomized blocks design, in a 3 × 2 factorial arrangement, was used. Three cover crops (palisade grass, millet and common bean) provided straw and root residues to the following crops of corn and soybean. The common bean-soybean sequence provided little soil covering and higher metabolic quotient and soil basal respiration and total enzymatic activity, as well as a general increase of soilborne fungi. The principal component analysis revealed that 76.61 % of the variance can be explained by the three first components, with cover crops, soil basal respiration and metabolic quotient regarded as the main qualitative and quantitative sources of variance in the first component. Carbon from the microbial biomass was the soil quality indicator best correlated to crop yield and negatively correlated to Fusarium solani density. The Rhizoctonia solani population was correlated with higher metabolic quotient and soil total enzymatic activity and basal respiration. The palisade grass crop favored soil fungistasis and enhancement of antagonist Trichoderma spp. populations. The multivariate approach demonstrated the association of soil fungi with soil quality indicators, as well as a higher influence of cover crops on the variance observed, in comparison to cash crops.