Abstract
The aims of this study were to evaluate: (1) the effect of sodium chloride (NaCl) and mannitol at different osmotic pressures on the germination of three proso millet (Panicum miliaceum L.) genotypes (VIR 9181, Unikum, and Kinelskoje) under controlled laboratory conditions; and (2) the effects of irrigation water salinity, maximum crop evapotranspiration (ETm) restitution regimes, and arbuscular mycorrhizal fungi (AMF) inoculation on forage production in a marginal Mediterranean soil for the genotypes that showed the highest and lowest seed germination. In the laboratory experiment, the Unikum genotype showed the highest seed germination (95.1%), whereas the lowest was found for Kinelskoje (80.4%). Regardless of the osmoticum type, germination was significantly reduced by osmotic pressure increases. Unikum showed a higher fresh biomass yield (FBY) (620.4 ± 126.3 g m−2) than Kinelskoje (340.0 ± 73.5 g m−2). AMF inoculation did not influence FBY under salt conditions, while in the absence of salt conditions it significantly increased the Unikum FBY (+50.7%) as compared to the uninoculated treatment (552.5 ± 269 g m−2). The 25% ETm significantly reduced FBY in both genotypes (−86.2% and −84.1% for Unikum and Kinelskoje, respectively) sd compared to the 100% ETm treatments (1090.3 ± 49.7 g m−2 in Unikum and 587 ± 72.2 g m−2 in Kinelskoje). The obtained results give novel information about proso millet forage production in low-input agriculture in marginal semi-arid Mediterranean land.
Highlights
In semi-arid and arid regions, salinity is one of the major causes of land degradation [1,2] and leads to huge economic losses due to the reduction in total arable land area and crop productivity [3].Salts effects on agricultural soils are generally tied to soluble minerals present in irrigation water and high fertilization input [4,5]
Agronomy 2018, 8, 8 which disrupt the structure of enzymes and other macromolecules, damage cell organelles, reduce photosynthesis and respiration, inhibit protein synthesis, and induce ion deficiency [7,8]; (2) osmotic effects due to physiological drought because plants must maintain lower internal osmotic potential to prevent water from moving from the roots into the soil [9]; and (3) nutrient imbalances caused by depression in uptake and/or transport [10,11]
Under water stress conditions (25% ETm) arbuscular mycorrhizal fungi (AMF) inoculation increased shoot density but did not influence culm height. These results suggest that: (1) under water stress conditions (25% ETm), in the presence of AMF inoculation the increase in fresh biomass yield (FBY) can be attributed to higher shoot density; and (2) under well-watered conditions (100% ETm), the absence of a significant difference in the FBY
Summary
In semi-arid and arid regions, salinity is one of the major causes of land degradation [1,2] and leads to huge economic losses due to the reduction in total arable land area and crop productivity [3].Salts effects on agricultural soils are generally tied to soluble minerals present in irrigation water and high fertilization input [4,5]. Agronomy 2018, 8, 8 which disrupt the structure of enzymes and other macromolecules, damage cell organelles, reduce photosynthesis and respiration, inhibit protein synthesis, and induce ion deficiency [7,8]; (2) osmotic effects due to physiological drought because plants must maintain lower internal osmotic potential to prevent water from moving from the roots into the soil [9]; and (3) nutrient imbalances caused by depression in uptake and/or transport [10,11]. AMF symbiosis can exert positive effects on crop production [13,14,15,16] and improve plant tolerance to abiotic stresses [17,18,19,20,21] such as drought and salinity. Possible AMF-mediated adaptation mechanisms inducing plant tolerance to saline conditions [22] include: (1) nutrient uptake improvement, especially phosphorus (P) [23,24,25];
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