Showing papers by "Wade H. Elmer published in 2016"

The use of metallic oxide nanoparticles to enhance growth of tomatoes and eggplants in disease infested soil or soilless medium

Abstract: Nanoparticles (NP) have great potential in agriculture. For example, micronutrients have poor mobility in plants and poor availability in neutral soils, yet they play pivotal roles in root health. We investigated whether foliar sprays of micronutrient NP could affect plant health in disease infested soils. In the greenhouse, NP of AlO, CuO, FeO, MnO, NiO, and ZnO were sprayed on tomatoes and grown in soilless medium infested with the Fusarium wilt fungus. NP of CuO, MnO, or ZnO reduced disease estimates [area-under-the-disease-progress-curve (AUDPC)] by 31%, 28%, or 28%, respectively, when compared to untreated controls. When NP of CuO, MnO, or ZnO, their bulked equivalents, or their sulfate salts were compared to untreated eggplants and held in the greenhouse in soilless medium infested with the Verticillium wilt fungus, NP of CuO increased fresh weights by 64%, reduced AUDPC values by 69%, and had 32% more Cu in the roots. These same amendments were sprayed onto the foliage of tomato and eggplant transplants and set in field plots in soil heavily infested with the Verticillium wilt fungus. Compared to untreated controls, yields of tomato were 33% or 31% greater with NP of CuO or the bulked MnO, respectively. NP of CuO or ZnSO4 increased eggplant yields by 34% or 41% when compared to controls, respectively. In vitro studies found NP of CuO were not inhibitory to the Fusarium wilt fungus, suggesting host defense was being manipulated.

Effect of Leaf Mold Mulch, Biochar, and Earthworms on Mycorrhizal Colonization and Yield of Asparagus Affected by Fusarium Crown and Root Rot.

Abstract: Asparagus can suffer from a crown and root rot caused by Fusarium oxysporum f. sp. asparagi and F. proliferatum. The disease is exacerbated when allelopathic toxins from old, rotting asparagus crowns are present in the soil. To minimize the damage from the replant problem, three strategies were examined: (i) biochar, (ii) application of earthworms (Lumbricus terrestris), and (iii) leaf mold to serve as a compost mulch and food source for earthworms. In a greenhouse, asparagus transplants were grown in soil amended with pathogen-infested asparagus residues or in nonamended soil, then both types of soil were augmented with biochar, earthworms, the combination of biochar and earthworms, or no treatment. Biochar increased arbuscular mycorrhizae (AM) colonization by 170% and reduced the incidence of root lesions by 57%; however, plant weight was not affected by any of the soil treatments and there were no significant interactions among the main effects. In the absence of infested asparagus residues, biochar reduced plant growth by 32%. Field plots that had severe crown and root rot, along with two other fields that had never been planted to asparagus, were planted with asparagus crowns and treated with leaf mold mulch, earthworms plus leaf mold mulch, biochar, or biochar plus earthworms plus leaf mold mulch. Untreated plots served as the control treatment. One year later, asparagus roots sampled from plots in the two new fields had a threefold increase in AM colonization when treated with biochar compared with control plots. Biochar did not increase yield over the duration of the 2012 to 2014 harvests when compared with that of the control plots. No soil treatment affected root colonization by AM in the field where Fusarium crown and root rot was severe. Compared with the untreated control plots, the leaf mold mulch treatment applied alone increased the marketable yields in each year of harvest. Combining leaf mold with earthworms provided no added benefit. Soil amendment with leaf mulch alone may hold promise for improving asparagus production in newly planted asparagus fields.

Pathogenic Microfungi Associated with Spartina in Salt Marshes

Abstract: Diebacks associated with disease in salt marshes are not as frequently observed as in terrestrial systems. However, when they do occur, the ecological costs to the marsh system can vary from devastation, in the case of Sudden Vegetation Dieback, to a minor cost, as in the case of Spartina rust outbreaks. All major diebacks of Spartina alterniflora have occurred along its native range in the western Atlantic and Gulf Coast. Fungi, herbivores, and abiotic stressors are frequently associated with the dieback. Many dieback/disease events have occurred as a result of fungal pathogens being introduced on invasive S. alterniflora. The dieback of the native common reed grass Phragmites australis in Shanghai, China, was found to be associated with F. palustre being vectored on S. alterniflora where it spread onto Phr. australis. Another example was where S. alterniflora presumably introduced the Spartina strain of ergot (Claviceps purpurea) to Europe where it increased on Spartina anglica. Although ergot was already present on the native Spartina foliosa in the eastern Pacific Coast marshes, the more resistant and robust hybrids that resulted between the invasive S. alterniflora and native S. foliosa were selectively favored over the native S. foliosa, thus advancing the dominance of the hybrids in these marshes. The incidence of Spartina rust incited by Puccinia sparganioidis is frequently seen in the marsh, but the rust is not considered to have a significant ecological cost to the marsh. The main economic concern is the disfigurement it can cause to its alternate host, ash (Fraxinus spp.). The last fungus discussed (Phaeosphaeria spartinicola) did not incite disease, but was highlighted due to its important function as a saprobe and in its facultative, mutualistic relationship with the herbivorous periwinkle snail. During periods of drought, these two organisms interacted in a way that led to massive dieback. Given the resilience of Spartina spp., it is surprising when these fungi cause significant damage. Most disease problems, however, tend to be associated with global spread of S. alterniflora into nonnative habitats.

Incidence of Fusarium spp. on the invasive Spartina alterniflora on Chongming Island, Shanghai, China

Abstract: Fusarium palustre is an endophyte/pathogen of Spartina alterniflora, a saltmarsh grass native to North America that has been associated in the USA with a saltmarsh decline known as Sudden Vegetation Dieback (SVD). Since the intentional introduction of S. alterniflora to stabilize mud flats on Chongming Island, Shanghai, China, S. alterniflora has become invasive, but shows no symptoms of dieback even though F. palustre can be isolated from the plant. When declining S. alterniflora from SVD sites in the northeastern USA were assayed for Fusarium species, an average of 8 % of tissues sampled gave rise to a species of Fusarium of these, 64 % were F. palustre and 16 % were F. incarnatum, a nonpathogenic species. To determine if low densities of F. palustre could explain the lack of dieback symptoms on S. alterniflora from Chongming Island, we assessed the incidence and distribution of Fusarium spp. on S. alterniflora from 12 sites on Chongming Island. On average, 26 % of the stem and root tissues sampled were colonized by a Fusarium species. Of 196 isolates recovered from S. alterniflora, 44 % were F. incarnatum and 41 % were F. palustre. Species determinations were confirmed for a subset of these isolates using a phylogenetic analysis of partial sequences of the translation elongation factor (tef) gene. The observation that Fusarium incidence on S. alterniflora was much greater on Chongming Island than in the USA survey raises the question as to why S. alterniflora on Chongming Island is showing no dieback. Other factors, such as predator release, enhanced nutritional, edaphic and/or other unidentified environmental constraints on Chongming Island may afford S. alterniflora protection from dieback.