Effect of organic amendments on sclerotial germination, mycelial growth, and Sclerotium rolfsii-induced diseases

Abstract

The addition of organic residues to soil is an option to control some soil-borne diseases. Benzaldehyde and powders of kudzu (Pueraria lobata), velvetbean (Mucuna deeringiana), and pine-bark (Pinus elliottii and P. taeda) added to soil could reduce certain soil-borne diseases. This study evaluated the effects of benzaldehyde and the dried powders of kudzu, velvetbean, and pine-bark as soil amendments on germination and formation of sclerotia, on mycelial growth of Sclerotium rolfsii, on plant survival, and disease incidence. The data showed that high amounts of benzaldehyde (0.4 ml kg-1 of soil) and velvetbean (100 g kg-1) inhibited S. rolfsii mycelial growth and sclerotium germination. However, low amounts of benzaldehyde (0.1 ml kg-1), kudzu (25 g kg-1), and pine-bark (25 g kg-1) stimulated mycelial growth and sclerotium germination. Kudzu (25-100 g kg-1) and velvetbean (25-100 g kg-1) inhibited the formation of sclerotia. Nevertheless, benzaldehyde at 0.2 and 0.4 ml kg-1 stimulated the formation of sclerotia. Kudzu (50 and 100 g kg-1) and pine-bark (50 g kg-1) favored the colonization of sclerotia by Trichoderma sp. The numbers of soybean (Glycine max) plants were higher and diseased plants were lower than the non-amend soil in the following treatments: kudzu (50 and 100 g kg-1), velvetbean (50 and 100 g kg-1), and pine-bark (50 g kg-1). Disease severity on tomato (Lycopersicon esculentum) plants was low in soil treated with kudzu or velvetbean (30 and 35 g kg-1) and pine-bark (35 g kg-1). Dried powders of kudzu, velvetbean, or pine-bark added to soil can reduce disease by reducing pathogen inoculum.

Dried powders of velvetbean and pine bark added to soil reduce Rhizoctonia solani-induced disease on soybean

“…These results suggest that the mechanisms involved in disease suppression with all these amendments are different. Velvetbean initially reduced fungal mycelial (fungistatic effect) growth and increased soil enzymatic activity 30 d after application of the amendments, indicating high microbial activity in soil (Blum & Rodríguez-Kábana, 2004;KokalisBurelle & Rodríguez-Kábana, 1994a;Soler-Serratosa et al, 1996). Amendments with kudzu and pine bark were initially not very suppressive to mycelial growth and resulted in lower enzymatic activity compared to the activity with velvetbean amendments.…”

“…Five R. solani colonized oat seeds were put on soil surface, each set 1.5 cm apart in cross design. This method is a modification of Rodríguez-Kábana et al (1975) method's for screening of pesticides against S. rolfsii (Blum & Rodríguez-Kábana, 2004). Cups were then closed with a plastic lid with a small hole on it (2mm), to allow gas exchange, and incubated at 27 o C (Precision Scientific incubator -GCA Corporation, USA).…”

Powders of kudzu, velvetbean, and pine bark added to soil increase microbial population and reduce Southern blight of soybean

“…Infestation of soil with pathogen was made 2 days prior to application of the amendments. Sowing with 'Davis' soybean (10 seeds per pot) was done 30 days after application of the amendments [Plantings in amended soil prior to 30 days after application of the amendments are not recommended due to possible phytotoxic effects on soybean seedlings induced by the organic residues (Blum & Rodríguez-Kábana, 2004)]. Evaluation of disease incidence was done 30 days after sowing.…”

Studies on Native Isolates of Fungal and Bacterial Bio-agents against Collar Rot of Chickpea

“…Several control measures have been adopted for control of S. rolfsii by many scientists which includes biological control (Pandey and Chaube, 2004), cultural control (Blum andRodriguez-kabana, 2006 andPinheiro et al, 2010), and chemical control (Paula et al, 2011).…”