Sterols play a key role in various physiological processes of plants. Commonly, stigmasterol, β-sitosterol and campesterol represent the main plant sterols, and cholesterol is often reported as a trace sterol. Changes in plant sterols, especially in β-sitosterol/stigmasterol levels, can be induced by different biotic and abiotic factors. Plant parasitic nematodes, such as the root-knot nematode Meloidogyne incognita, are devastating pathogens known to circumvent plant defense mechanisms. In this study, we investigated the changes in sterols of agricultural important crops, Brassica juncea (brown mustard), Cucumis sativus (cucumber), Glycine max (soybean), Solanum lycopersicum (tomato) and Zea mays (corn), 21 days post inoculation (dpi) with M. incognita. The main changes affected the β-sitosterol/stigmasterol ratio, with an increase of β-sitosterol and a decrease of stigmasterol in S. lycopersicum, G. max, C. sativus and Z. mays. Furthermore, cholesterol levels increased in tomato, cucumber and corn, while cholesterol levels often were below the detection limit in the respective uninfected plants. To better understand the changes in the β-sitosterol/stigmasterol ratio, gene expression analysis was conducted in tomato cv. Moneymaker for the sterol 22C-desaturase gene CYP710A11, responsible for the conversion of β-sitosterol to stigmasterol. Our results showed that the expression of CYP710A11 was in line with the sterol profile of tomato after M. incognita infection. Since sterols play a key role in plant-pathogen interactions, this finding opens novel insights in plant nematode interactions.

Desferrioxamine is a siderophore produced by the fire blight pathogen E. amylovora under iron-limited conditions. In the present study, no or only weak induction of an iron-regulated promoter-GFP reporter was observed on semisterile apple flowers, and siderophore synthesis or uptake (receptor) mutants exhibited colonization of the flower and necrosis induction at parental levels.

New management practices must be developed to improve yam productivity. By allowing non-destructive analyses of important plant traits, image-based phenotyping techniques could help developing such practices. Our objective was to determine the potential of image-based phenotyping methods to assess traits relevant for tuber yield formation in yam grown in the glasshouse and in the field. We took plant and leaf pictures with consumer cameras. We used the numbers of image pixels to derive the shoot biomass and the total leaf surface and calculated the ‘triangular greenness index’ (TGI) which is an indicator of the leaf chlorophyll content. Under glasshouse conditions, the number of pixels obtained from nadir view (view from the top) was positively correlated to shoot biomass, and total leaf surface, while the TGI was negatively correlated to the SPAD values and nitrogen (N) content of diagnostic leaves. Pictures taken from nadir view in the field showed an increase in soil surface cover and a decrease in TGI with time. TGI was negatively correlated to SPAD values measured on diagnostic leaves but was not correlated to leaf N content. In conclusion, these phenotyping techniques deliver relevant results but need to be further developed and validated for application in yam.

The yeast Metschnikowia pulcherrima is frequently isolated from environmental samples and has often been reported to exhibit strong antagonistic activity against plant pathogens. In order to assess the potential of this species for its development into a plant protection product, the survival during formulation and storage were quantified and field efficacy was assessed over a period of five years. Freeze dried and liquid M. pulcherrima formulations (i.e., with skim milk powder (SMP), sucrose, glycerol, xanthan, without additives) were prepared and the number of viable cells was quantified during storage at different temperatures. Field trials against apple postharvest diseases (Neofabreae) were performed with different dry formulations. M. pulcherrima proved exceptionally stable for many months and even years. Five years of field trials with the yeast revealed variable effects, but reduced Neofabreae infections of stored apples were observed in some years. M. pulcherrima applications after prior fungicide treatments repeatedly showed an additive effect as compared to the fungicide treatments alone. In summary, M. pulcherrima exhibited highly advantageous storage properties and encouraging activity against apple postharvest rots. Further studies to identify the factors responsible for antagonistic activity in the field and survival during storage are expected to lay the foundation for the future development of a plant protection product.

Management practices must be developed to improve yam production sustainability. Image-based phenotyping techniques could help developing such practices based on non-destructive analyses of important plant traits. Our objective was to determine the potential of image-based phenotyping methods to assess traits relevant for tuber yield formation in yam grown in glasshouse and field. We took plant and leaf pictures with consumer cameras. We used the numbers of image pixels to derive the shoot biomass and the total leaf surface and calculated the ‘triangular greenness index’ (TGI) which is an indicator of the plant nitrogen (N) nutritional status. Under glasshouse conditions, the number of pixels obtained from nadir view (image taken top down) was positively correlated to the shoot biomass, and the total leaf surface, while the TGI was negatively correlated to the N content of diagnostic leaves. Under field conditions, pictures taken from the nadir view showed an increase in soil surface cover and a decrease in TGI with time. TGI was negatively correlated to SPAD measured on specific leaves but was not correlated to the N content of these leaves. In conclusion, these phenotyping techniques deliver relevant results but need to be further developed and validated for application in yam.