Effects of Soil-Applied Fungicides on Sugarcane Root and Shoot Growth, Rhizosphere Microbial Communities, and Nutrient Uptake

Abstract

Sugarcane (Saccharum spp. hybrid) successive planting (also called monoculture) causes serious yield losses and its management is not well studied in Histosols. Based on very few studies in other sugarcane regions, root colonization by harmful soil fungi is considered as a major cause of this yield decline, but there is lack of knowledge on its management in Histosols. A two-year greenhouse study was conducted with soil-drench application of mancozeb, mefenoxam, and azoxystrobin fungicides to determine their effects on early root and shoot growth, soil microbial communities, and nutrient uptake by plants. The study indicated that mancozeb soil application improved sugarcane-shoot and -root dry matter by 3–4 times and shoot-root length, fine-root length, and root surface area by 2–3 times compared to untreated soil. Phospholipid fatty acid (PLFA) analyses of sugarcane rhizosphere soil showed significant reduction in fungal-biomarker abundance with mancozeb and azoxystrobin in comparison to the untreated check or mefenoxam treatments. Bacterial functional-group abundance was reduced by mancozeb and mefenoxam. All fungicides significantly reduced mycorrhizal colonization but not mycorrhizal spore counts. There was a functional relationship between fine-root systems and higher tissue concentration of nitrogen and silicon. The study indicated that application of fungicides to the soil may improve early root and shoot growth and plant-cane establishment that can potentially reduce the yield decline in successively planted sugarcane in histosols. Additional field research is needed in the future to determine the fungicide soil application method, sugarcane growth response in whole crop cycles, and any environmental effects.

Fungicides With Contrasting Mode of Action Differentially Affect Hyphal Healing Mechanism in Gigaspora sp. and Rhizophagus irregularis

“…These authors demonstrated under similar in vitro culture conditions that azoxystrobin at 0.1 mg L −1 (as formulation Amistar) affected spore production and hyphal length of R. irregularis MUCL 41833 associated with potato, while root colonization was reduced at 1 (a.i., or formulation Amistar) and 10 mg L −1 a.i. Greenhouse studies further demonstrated that soil drench with azoxystrobin inhibited root colonization of Glomeraceae members in sugarcane (Vuyyuru et al, 2018). Moreover, root colonization and enzymatic activity of Funneliformis coronatum associated with maize plants was also inhibited, demonstrating the fungicidal activity of this strobilurin, probably on the respiratory electron transfer within mitochondria, where succinate dehydrogenase is part of complex II (Diedhiou et al, 2004).…”

Aspects, problems and utilization of Arbuscular Mycorrhizal (AM) application as bio-fertilizer in sustainable agriculture

“…(2015) . Though soil application of azoxystrobin inhibited root colonization of Glomeraceae members ( Vuyyuru et al., 2018 ), foliar application of azoxystrobin not affect AM root colonization ( Campos et al., 2015 ). Benomyl, Bavistin, Captan and Mancozeb were tested on association of R. fasciculatus with Panicum miliaceum L.The results of this study showed significant ( P ≤ 0.05) higher AM colonization, spore density, plant growth and grain yield treated with Captan compared to other fungicides and untreated controls.…”

“…(2015) . Though soil application of Azoxystrobin inhibited root colonization of Glomeraceae members, foliar application is safe ( Vuyyuru et al., 2018 ). Alternative use of similar less harmful fungicides or low doses may be practiced.…”

Effects of Nitrogen Fertilization and Seed Piece Applied Fungicides on Establishment, Tiller Dynamics, and Sucrose Yields in Successively Planted Sugarcane

“…The treatments were: (i) Untreated, (ii) Mancozeb 2.5 kg a.i ha −1 (Manzate Max ® , United Phosphorus Inc., King of Prussia, PA, USA), iii) Mefenoxam, 0.57 kg a.i ha −1 (Ridomil Gold ® 2E, Syngenta Corporation, Greensboro, NC, USA), and (iv) Azoxystrobin, 0.3 kg a.i ha −1 (Quadris ® 2.08SC, Syngenta Corporation, Greensboro, NC, USA). Further description of commercial formulations of these fungicides can be found in Vuyyuru et al [29]. Fungicides were topically applied as a 15 cm concentrated band over seed cane pieces in the furrows prior to covering with soil.…”

“…An alternate method, such as dipping the sets in a fungicidal solution, may be a better choice [12]. This may be the reason that mancozeb caused a significant improvement in sugarcane root and shoot growth in a greenhouse study [29] where the soil was drenched with a fungicide solution. In high organic matter soils, azoxystrobin was reported to be degraded faster by soil microbial communities [53], and greater response with mefenoxam may be due to its more systemic and persistent nature.…”