Phytohormone Priming of Tomato Plants Evoke Differential Behavior in Rhizoctonia solani During Infection, With Salicylate Priming Imparting Greater Tolerance Than Jasmonate

In the field of phytohormone defense, the general perception is that salicylate (SA)-mediated defense is induced against biotrophic pathogens while jasmonate (JA)-mediated defense functions against necrotrophic pathogens. Our goals were to observe the behavior of the necrotrophic pathogen Rhizoctonia solani in the vicinity, on the surface, and within the host tissue after priming the host with SA or JA, and to see if priming with these phytohormones would affect the host defense differently upon infection. It was observed for the first time, that R. solani could not only distinguish between JA versus SA-primed tomato plants from a distance, but surprisingly avoided SA-primed plants more than JA-primed plants. To corroborate these findings, early infection events were monitored and compared through microscopy, Scanning Electron Microscopy, and Confocal Laser Scanning Microscopy using transformed R. solani expressing green fluorescence protein gene (gfp). Different histochemical and physiological parameters were compared between the unprimed control, JA-primed, and SA-primed plants after infection. The expression of a total of fifteen genes, including the appressoria-related gene of the pathogen and twelve marker genes functioning in the SA and JA signaling pathways, were monitored over a time course during early infection stages. R. solani being traditionally designated as a necrotroph, the major unexpected observations were that Salicylate priming offered better tolerance than Jasmonate priming and that it was mediated through the activation of SA-mediated defense during the initial phase of infection, followed by JA-mediated defense in the later phase. Hence, the present scenario of biphasic SA-JA defense cascades during R. solani infection, with SA priming imparting maximum tolerance, indicate a possible hemibiotrophic pathosystem that needs to be investigated further.

Use of Lentinan and Fluopimomide to Control Cotton Seedling Damping-Off Disease Caused by Rhizoctonia solani

Lentinan (LNT) is a natural and functional polysaccharide isolated from Lentinus edodes fruiting bodies, which functions in stimulating the plant immune response, improving plant disease resistance and regulating plant growth. This study explores the use of LNT as a plant growth regulator and attractant in cotton production. After treatment with LNT, the content of malondialdehyde (MDA) in cotton seeds decreased, whereas the activities of polyphenol oxidase (PPO), superoxide dismutase (SOD) and peroxidase (POD) in leaves increased significantly. LNT also promoted the growth and development of cotton plants and significantly reduced the incidence of cotton damping-off disease. The relative expression of salicylic acid pathway-related genes in cotton also increased significantly. The prevention mechanism of fluopimomide was also evaluated, and the result showed lower EC50 values and was effective in controlling cotton seedling disease caused by Rhizoctonia solani in both greenhouse experiments and field trials. The use of LNT and fluopimomide in controlling cotton seedling damping-off disease showed a synergistic effect in field trials. These results will provide a new insight into the agricultural application of LNT as a biological fungicide in the field of biological controls.

Surveillance of Pathogenicity of Rhizoctonia solani Japanese Isolates with Varied Anastomosis Groups and Subgroups on Arabidopsis thaliana

Rhizoctonia solani is a necrotrophic plant pathogen with a wide host range. R. solani is a species complex consisting of thirteen anastomosis groups (AGs) defined by compatibility of hyphal fusion reaction and subgroups based on cultural morphology. The relationship between such classifications and host specificity remains elusive. Here, we investigated the pathogenicity of seventeen R. solani isolates (AG-1 to 7) in Japan towards Arabidopsis thaliana using leaf and soil inoculations. The tested AGs, except AG-3 and AG-6, induced symptoms in both methods with variations in pathogenicity. The virulence levels differed even within the same AG and subgroup. Some isolates showed tissue-specific infection behavior. Thus, the AGs and their subgroups are suggested to be not enough to define the virulence (host and tissue specificity) of R. solani. We also evaluated the virulence of the isolates on Arabidopsis plants pretreated with salicylic acid, jasmonic acid, and ethylene. No obvious effects were detected on the symptom formation by the virulence isolates, but ethylene and salicylic acid slightly enhanced the susceptibility to the weak and nonvirulent isolates. R. solani seems to be able to overcome the induced defense by these phytohormones in the infection to Arabidopsis.

تأثير بعض أنواع الفطريات على استنبات بذور الفول fababean صنف Minor في ليبيا

أُجريت التجربة خلال عامي 2019- 2020 في معمل أمراض النبات – كلية الزراعة – جامعة عمر المختار، بهدف دراسة تأثير البعض من أنواع الفطريات تضمنت Botrytis cinerea، Macrophomina phaseolina، Rhizoctonia solani، Sclerotinia sclerotiorum و Trichoderma harzianum على نسبة، وسرعة الإنبات، ومستوى تعفن الجذور في بذور الفول صنف Minor معملياً. تم تحضين البذور بعد تعقيمها سطحياً، وزراعتها في أطباق بتري على الوسط WA 1% الملقح بالفطريات المدروسة. سجلت التجربة اختلافات معنوية في نسبة الإنبات، و سرعته، ومستوى المرض. أفضل إنبات للبذور كان في معاملة T. harzianum (91.7%)، ولكن ليس أكثر من الشاهد (%100)، وأقل إنبات (25%) كان في البذور المعاملة بالفطرين M. phaseolina وR. Solani. كانت أعلى سرعة إنبات (3.1) للبذور في محيط Trichoderma أكثر من بذور الشاهد، والفطريات المُمْرِضة، في حين وصل مستوى المرض أعلاه (4.8) على الجُذير في معاملة الفطر R. solani، وسجل (0) في مُعاملتي الــــTrichoderma والشاهد. نستنتج من الدراسة أن معاملة البذور بالفطر T. harzianum يمكن أن تكون مفيدة لتحسين إنبات بذور الفول، بالإضافة إلى خفض الإنبات المتأخر.

In Silico Inhibitability of Copper Carbenes and Silylenes against Rhizoctonia solani and Magnaporthe oryzae

Copper lighter tetrylenes are promising for inhibition towards Rhizoctonia solani-based protein PDB-4G9M and Magnaporthe oryzae-based PDB-6JBR in rice. Quantum properties of four hypothetic copper complexes of carbenes and silylenes (Cu-NHC1, Cu-NHC2, Cu-NHSi1, and Cu-NHSi2) were examined using the density functional theory. Their inhibitability towards the targeted proteins was evaluated using molecular docking simulation. Quantum analysis predicts the stability of the investigated complexes and thus their practical existability and practicable synthesisability. Their electronic configurations are justified as highly conducive to intermolecular interaction. Regarding ligand-protein as carbenes/silylenes-4G9M inhibitory structures, the stability is estimated in the order [Cu-NHC2]-4G9M (DS −12.9 kcal⋅mol−1) > [Cu-NHSi1]-4G9M (DS −11.8 kcal⋅mol−1) = [Cu-NHSi2]-4G9M (DS −11.7 kcal⋅mol−1) > [Cu-NHC1]-4G9M (DS –11.4 kcal⋅mol−1). In contrast, the corresponding order for the carbenes/silylenes-6JBR systems is [Cu-NHSi2]-6JBR (DS –13.4 kcal⋅mol−1) > [Cu-NHC2]-6JBR (DS −13.0 kcal⋅mol−1) = [Cu-NHSi1]-6JBR (DS −12.6 kcal⋅mol−1) > [Cu-NHC1]-6JBR (DS −12.3 kcal⋅mol−1). In theory, this study suggests a potentiality of copper lighter tetrylenes and their derivatives against the infection of fungi Rhizoctonia solani and Magnaporthe oryzae, thus encouraging attempts for experimental developments.

RNA-seq analysis of Rhizoctonia solani AG-4HGI strain BJ-1H infected by a new viral strain of Rhizoctonia solani partitivirus 2 reveals a potential mechanism for hypovirulence

Rhizoctonia solani partitivirus 2 (RsPV2), in the genus Alphapartitivirus, confers hypovirulence on Rhizoctonia solani AG-1-IA, the causal agent of rice sheath blight. In this study, a new strain of RsPV2 obtained from R. solani AG-4HGI strain BJ-1H, the causal agent of black scurf on potato, was identified and designated as Rhizoctonia solani partitivirus 2 strain BJ-1H (RsPV2-BJ). An RNA sequencing analysis of strain BJ-1H and the virus RsPV2-BJ-free strain BJ-1H-VF derived from strain BJ-1H was conducted to investigate the potential molecular mechanism of hypovirulence induced by RsPV2-BJ. In total, 14319 unigenes were obtained, and 1341 unigenes were identified as differentially expressed genes (DEGs), with 570 DEGs being down-regulated and 771 being up-regulated. Notably, several up-regulated DEGs were annotated to cell-wall-degrading enzymes, including β-1,3-glucanases. Strain BJ-1H exhibited increased expression of β-1,3-glucanase following RsPV2-BJ infection, suggesting that cell wall autolysis activity in R. solani AG-4HGI strain BJ-1H might be promoted by RsPV2-BJ, inducing hypovirulence in its host fungus R. solani AG-4HGI. To the best of our knowledge, this is the first report on the potential mechanism of hypovirulence induced by a mycovirus in R. solani.