Abstract
Downy mildew (Peronospora belbahrii) is a major disease of sweet basil (Ocimum basilicum). We examined the effects of potassium, calcium and magnesium, individually and in combination, on sweet basil downy mildew (SBDM) in potted plants and under commercial-greenhouse conditions over six growing seasons. An increased K concentration in the fertigation solution increased SBDM severity, whereas foliar-applied KCl and K2SO4 suppressed SBDM. The application of higher concentrations of those salts increased the K concentrations in the shoots and significantly alleviated SBDM. Increased concentrations of Ca or Mg in the fertigation solution decreased SBDM severity, as did foliar-applied CaCl2. However, the combination of Ca and Mg did not have any synergistic effect. Foliar-applied K2SO4 provided better disease suppression than some of these treatments. The 3.3 mM Mg + fungicide treatment and the 5.0 mM Mg + fungicide treatment each provided synergistic disease control in one of two experiments. SBDM severity was significantly reduced by MgCl2 and MgSO4 (both 3.3 mM Mg), as compared with the basic Mg fertigation (1.6 mM), with MgCl2 providing better control. The combined Mg salts + fungicide treatments reduced SBDM better than any of those treatments alone. These results demonstrate that macro-elements can contribute to SBDM control.
Highlights
Macro-elements play an important role in plant nutrition and plant health
Raising the concentration of K in the fertigation solution from 0.5 to 5.1 mM increased the concentration of K in the shoots (Figure 2a), as well as a sweet basil downy mildew (SBDM) severity (Figure 2b)
The shoot yield was low at the two lower K concentrations, while at 4.11 to 5.79 mM K, there were no significant changes in yield between treatment (Figure 2d)
Summary
Macro-elements play an important role in plant nutrition and plant health. The cations K+ , Ca2+ and Mg2+ are important [1,2]. K+ is the most abundant cation in plant tissue; its concentration in the cytoplasm reaches 200 mM, and it accounts for up to 6% of dry plant weight [3]. K+ is readily translocated in the phloem and xylem and moves through tissues and into cells via K channels [4]. K+ helps to regulate the electrical charge in cells and control the acidity of the cytosol and chloroplasts and plays a role in enzymatic reactions [5]. K+ affects the process of photosynthesis, including the turgor pressure that opens and closes stomata, other osmoregulation, cell elongation, upregulation of enzyme expression and protein synthesis [3,6].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
