The aim of this study was to determine the oomycetous pathogens causing root rot on sugar beet and test their control by seed treatment in Konya Province, Turkey. Oomycetous fungus-like pathogens of sugar beet were investigated using 866 plant samples collected at 2 growth stages, early seedling and late root, from fields in the Konya region of Turkey and 1 sample from the Thrace region. Herein, 10 oomycetous species belonging to 3 genera: Aphanomyces cochlioides, Phytophthora cryptogea, Ph. pseudocryptogea, Ph. megasperma, Ph. inundata, Pythium aphanidermatum, Py. helicoides, Py. heterothallicum, Py. sylvaticum, and Py. ultimum var. ultimum (Globisporangium ultimum var. ultimum) were discovered at various times with in the 2 growth periods, all of which were the first records for Turkey. A. cochlioides was the most serious pathogen, both in terms of its wide distribution and aggressiveness. The pathogen produced more than 90% disease severity when tested by soil infestation at the seedling stage, although it also occurred at the late root growth stage. Pythium species were also ascommon, such as A. cochlioides, the majority of which were very aggressive, producing more than 84% disease severity at the seedling stage, except for Py. aphanidermatum. Half-strength potato dextrose agar medium was found to be very useful for the isolation of all of the pathogens from the plant samples at both stages. Morphological features of all of the pathogens were abundantly produced when the pathogens were grown on amended grated carrot agar medium and culture disks of fungal growth of this medium were submerged in sterile and nonsterile soil extracts. Out of the 15 fungicide mixes tested, 2 mixes, thiram+metalaxyl+hymexazole and thiram+metalaxyl+hymexazole+ pyraclostrobin reduced seedling root rot caused by both A. cochlioides and Pythium ultimum var. ultimum, while the standard seed treatment fungicide mix of thiram+hymexazole was not effective against either of the pathogens.

This study assessed the efficacy of chitosan, methyl jasmonate, and silicon in the reduction of disease severity and the induction of defense responses in common bean plants against angular leaf spot caused by Pseudocercospora griseola. The expression level of several pathogenesis-related (PR) proteins, PR1, PR2 (β-1,3-glucanase), and PR3 (chitinase), and defense-related enzymes, phenylalanine ammonia-lyase, peroxidase, and lipoxygenase, was analyzed at different time points in common bean plants after different treatments. Elicitor treatments significantly reduced disease severity 21 days after inoculation, with silicon at a 2 mM concentration proving most effective with 38.93% disease control, followed by 1 mM MeJA and 2% chitosan, respectively. Treatments with chitosan, methyl jasmonate, and silicon, regardless of pathogen infection, significantly elevated PR1, PR2, and PR3 gene expressions at 48 h after inoculation (hpi). PAL and POD activities were similarly increased following elicitor treatments and pathogen infection, especially at 48 hpi. Chemical elicitors applied post-inoculation induced PR proteins, PAL, and POD enzyme activities at 48 hpi, while LOX activity exhibited a variable fluctuation with treatments. These findings suggested that chemical elicitors, especially silicon, were effective in reducing ALS disease severity in common beans, with improved resistance associated with the expression of pathogen-responsive genes. This study is the first to analyze the expression profiles of defense-related genes in common beans treated with chemical elicitors prior to P. griseola infection.