Pea (Pisum sativum L.) cultivars with low accumulation of heavy metals from contaminated soil

Heavy metals are among the most common contaminants of agricultural lands. Cleaning (remediation) of such territories is extremely difficult or impossible. A promising approach for the production of environmentally friendly products of crop industry in the contaminated soils can be a selection of varieties with reduced accumulation of heavy metals. The aim of this work was to study the variability of pea in accumulation and transport of heavy metals from shoots to seeds and to identify varieties with low accumulation of heavy metals from contaminated soils. The objects of research were 30 varieties of pea ( Pisum sativum L.) from the collection of Federal Research Center N.I. Vavilov All-Russia Institute of Plant Genetic Resources (St. Petersburg). The pot experiment was carried out in summer in a greenhouse with natural light and temperature (All-Russian Research Institute of Agricultural Microbiology, St. Petersburg). Pea seeds were surface-sterilized and scribbled with concentrated H2SO4 for 30 minutes and germinated for 3 days at 22 °C in Petri dishes with wet filter paper. The seedlings were planted in pots (5 seedlings per pot, 3 pots for each genotype) containing 5 kg of sod-podzolic fallow soil. Ten days before seed sowing the soil was enriched with heavy metals in the form of chlorides (mg/kg): Cd - 5, Co - 25, Cr - 60, Cu - 10, Ni - 15, Pb - 100, Sr - 50, Zn - 50. At the same time, fertilizers were applied (mg/kg): NH4NO3 - 15, KNO3 - 200, KH2PO4 - 200, MgSO4 - 30, CaCl2 - 20, H3BO3 - 3, MnSO4 - 3, ZnSO4 - 3, Na2MoO4 - 1.5. The plants were grown until the seed maturing phase, dried and ground to a powder. Samples (separately shoots and seeds) were digested in a mixture of concentrated nitric acid and 38 % H2O2. The content of heavy metals and nutrients was determined using ICPE-9000 spectrometer (Shimadzu, Japan). The studied samples differed significantly in the content of heavy metals in shoots and seeds that indicated a high variability of pea in the accumulation of heavy metals and their transport from vegetative to reproductive organs. The variability values for shoots and seeds were comparable in magnitude, but did not correlate with each other. The shoots or seed contents of various heavy metals, as well as nutrients, in many cases positively correlated, which could be due to the diversity of molecular transport channels in plants and their low specificity. There was positive correlation between the content of elements in shoots and seeds for Cd, Co, Cr, Ni, P, Sr, and negative was found between the shoot and seed contents of Zn and K. The results indicate specific mechanisms of transport of individual elements from shoot to seed and the barrier for abiogenic metal transport from vegetative to reproductive organs. The effectiveness of these mechanisms depends significantly on the plant genotype. The possibility of selection of pea varieties with a low content of many heavy metals simultaneously is shown. Pea varieties k-188, k-1027, k-1250, k-2593, k-3445, k-4788, k-5012, k-6468, k-8093 and k-8543 are recommended for use in selection programs for obtaining ecologically safe crop production.