In this study, different maize fields cultivated under different management systems were sampled to test corn leaf aphid, Rhopalosiphum maidis, populations in terms of total and endosymbiotic bacterial diversity. Corn leaf aphid natural populations were collected from traditionally managed maize fields grown under high agricultural and natural landscape diversity as well as conventionally treated high-input agricultural fields grown in monoculture and with fertilizers use, hence with low natural landscape diversity. Total bacterial community assessment by DNA sequencing was performed using the Illumina MiSeq platform. In total, 365 bacterial genera were identified and 6 endosymbiont taxa. A high abundance of the primary endosymbiont Buchnera and secondary symbionts Serratia and Wolbachia were detected in all maize crops. Their frequency was found to be correlated with the maize management system used, probably with fertilizer input. Three other facultative endosymbionts (“Candidatus Hamiltonella”, an uncultured Rickettsiales genus, and Spiroplasma) were also recorded at different frequencies under the two management regimes. Principal components analyses revealed that the relative contribution of the obligate and dominant symbiont Buchnera to the aphid endosymbiotic bacterial community was 72%, whereas for the managed system this was only 16.3%. When facultative symbionts alone were considered, the effect of management system revealed a DNA diversity of 23.3%.

Studies conducted in controlled environments showed that seed priming and foliar treatments with various bioactive substances can stimulate germination, uniform seedling emergence, photosynthesis, and nutrient uptake efficiency and can lead to increased productivity, crop stand, and quality. Only a few studies provide a comparative experimental outlook about the use of the bioactive substances in open-field cultivated canola. The aim of this study was to investigate the effects of seed priming and foliar treatment with ascorbate (AsA), cysteine (Cys), and triacontanol (Tria) on the growth and yield parameters of two canola cultivars rapeseed cultivars (“Factor” and “Hybrirock”) under open-field conditions for three growing seasons under temperate conditions from Central Transylvania. Plant growth and yield parameters were recorded at different plant development stages: in autumn (early vegetative period), in spring, and at harvest. Not all substances that have undergone laboratory testing were successful in the field. Seed priming with 10 ppm Cys and AsA had beneficial effects on the development of seedlings, whereas their foliar application enhanced the number of silique, seed yield, and the oil content of the studied canola cultivars. The effects of Tria were visible on the biometrics parameters only in autumn and spring, and also on the root parameters, but in some cases, 10 ppm Tria had no effect on plants, or even a negative effect could be observed on important parameters for agriculture such as estimated seed yield, seed yield/plant, and oil content. Optimizing treatment and application by determination of the lowest effective concentration, together with the frequency of treatments and persistence effects are crucial for cost-effectiveness.

Seeds of industrial hemp have high nutritional and healthcare value, which can be further improved by proper cultivation methods. Biochemical properties of hemp seeds that are beneficial for human use can be modulated through variation of the molar ratio between the inorganic nitrogen and phosphorus supplied with the nutrient medium, as well as by creating a moderate water deficit during controlled irrigation. The aim of this study was to investigate the influence of two N:P ratios (i.e. 8 mM nitrogen as nitrate to 2 mM phosphorus as phosphate, and 3 mM nitrogen to 6 mM phosphorus), combined with two water supply regimes (sufficient and insufficient) on vegetative growth parameters, seed production, seed oil, protein, vitamin E, iron, zinc and manganese content of two industrial hemp cultivars (‘Jubileu’ and ‘Zenit’). The experiments were performed in a greenhouse, under controlled conditions. Even if plants receiving a lower N:P ratio and lower water supply had a decreased growth index and the shoot fresh weight was smaller, no statistically significant difference could be registered in the seed production of the different experimental variants. The oil content of seeds could be increased by a lower N:P ratio and by water deficit, while seed protein content was higher upon a higher N:P ratio and upon water shortage, for both cultivars. The highest vitamin E content of hemp seed oil was found when plants were subjected to the combined influence of lowered N:P ratio and water insufficiency. The iron content of seeds showed no changes between the different experimental variants. In seeds of the ‘Jubileu’ variety the zinc content was increased by water shortage when the N:P ratio was lower, while the highest manganese content was measured when plants received sufficient water and lowered N:P ratio. As for the ‘Zenit’ variety, the highest zinc and manganese content of seeds was obtained when plants received through the nutrient solution 8 mM nitrate and 2 mM phosphate (i.e. the N:P ratio was 4:1). The findings may contribute to optimization of hemp cultivation, in a cost-effective and environmental-friendly approach, for the purpose of production of higher quality seeds for human and animal consumption, as well as for the cosmetic industry.