Abstract
Little is known about the effects of nitrogen supply on plant productivity and defensive response to pathogen exposure. Here, tuber yield and resistance to the fungal pathogen Phytophthora infestans were investigated in potato plants supplied with four different nitrogen levels (N1: 45 kg-hm-2, N2: 90 kg-hm-2, N3: 135 kg-hm-2, and N4: 180 kg-hm-2). The N2 level of nitrogen promoted the highest tuber yield and largest tubers under pathogen-free conditions. However, N3 promoted the strongest pathogen resistance and highest potato production in response to P. infestans exposure. Also, the highest level of chlorophyll accumulation was observed with N3 relative to the other treatment groups under pathogen-infected but not pathogen-free conditions. Further study showed that, in response to pathogen infection, the N3 level of nitrogen induced the highest activity levels for the defensive enzymes polyphenol oxidase and phenylalanine ammonia-lyase (but not chitinase and β-1,3-glucanase) and the most abundant accumulation of phenolic and flavonoid compounds. Our data demonstrated that modest increases in the nitrogen supply provided potato plants with optimum growth and defensive capability in response to P. infestans exposure. Key words: Nitrogen, tuber yield, pathogen resistance, Phytophthora infestans, Solanum tuberosum.
Highlights
Because plants are sessile in nature and provide a rich source of nutrients for many organisms in the environment, they have developed a wide array of structural, chemical, and protein-based defenses designed to detect invading organisms and protect themselves from extensive damage
Nitrogen is a mobile nutrient in the soil, and nitrogen levels have a significant impact on tuber yield and size in a potato crop (Saeidi et al, 2009)
Phytophthora infestans is an important fungal pathogen for potato plants and the cause of the late blight disease in potato, which can result in a significant reduction in tuber yield (Moller et al, 2006)
Summary
Because plants are sessile in nature and provide a rich source of nutrients for many organisms in the environment, they have developed a wide array of structural, chemical, and protein-based defenses designed to detect invading organisms and protect themselves from extensive damage. Nitrogen is a mobile nutrient in the soil, and nitrogen levels have a significant impact on tuber yield and size in a potato crop (Saeidi et al, 2009). Phytophthora infestans is an important fungal pathogen for potato plants and the cause of the late blight disease in potato, which can result in a significant reduction in tuber yield (Moller et al, 2006). Nitrogen levels can have a significant impact on potato yield and tuber size (Saeidi et al, 2009). How does P. infestans affect potato tuber yield and size and the defense response with different nitrogen levels? We investigated whether strong resistance to pathogens would be compatible with high yield in potato plants with the rise of nitrogen availability. This work provided us with insight into the relationship between P. infestans resistance and plant yield under various nitrogen conditions
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