Evaluation of the symbiotic effectiveness of pea (Pisum sativum L.) genotypes in pot experiment

The successful use of plant-microbe systems based on legumes in agriculture requires creation of new cultivars of crop legumes effectively interacting with microbes. For the selection of cultivars of crop legumes, the effectiveness of interaction with beneficial soil microorganisms (EIBSM) trait has been proposed. EIBSM is estimated as a percentage of increment in a number of agriculturally important parameters (plant biomass, number and total biomass of seeds, as well as weight of 1000 seeds) after applying the microbial inoculum compared to untreated control. The aim of this study was to evaluate the EIBSM trait in a pot experiment involving two pea ( Pisum sativum L.) genotypes that have shown high and low effectiveness of interaction with beneficial soil microflora in a three-year field experiment. The highly effective in symbiosis with nodule bacteria and arbuscular-mycorrhizal fungi genotype k-8274 (France, cv. Vendevil) and ineffective genotype k-3358 (Saratov region, Russia) from the VIR Collection of cultivated peas of N.I. Vavilov All-Russian Institute of Plant Genetic Resources were used in the study. Plants were grown during the summer season of 2012 in a greenhouse in the 5-liter pots on sod-podzolic light loamy soil. Treatment variants were as follows: control (untreated soil); nodule bacteria + arbuscular mycorrhizal fungi (NB + AMF); nodule bacteria (NB); mineral nutrition (NPK). Variants of soil moisture were as follows: low moisture (watering with 30 % of full moisture capacity, FMC) and optimal moisture (watering with 60 % of FMC). Mineral fertilizers (NPK) were applied in the form of pure salts in a dose of 0.1 mg a.i. per 1 kg of soil. For NB inoculation, the effective strain Rhizobium leguminosarum bv. viciae RCAM1026 was used. AM fungi for inoculation were propagated on the sorghum ( Sorghum sp.) roots. A mixed inoculum containing three AMF isolates, Rhizophagus irregularis (syn. Glomus intraradices ) RCAM8 (= BEG144), R. irregularis BEG53 and Glomus sp. ST3, was applied. Samples were gathered at the budding stage, after 1 month of vegetation (to determine the amount of nodules and the dry plant biomass) and at the end of vegetation about 3 months after planting (to determine the dry plant biomass, seed weight and amount). When grown in pots, highly effective and ineffective genotypes demonstrated the expected differences in EIBSM. The dry weight after 1 month of vegetation of highly effective k-8274 genotype showed a statistically significant increase in the NB and NPK variants compared to the control. At the same time, this parameter in the ineffective genotype k-3358 significantly increased only under the influence of mineral nutrition, but not nodule bacteria. Also, under treatment of NB, k-8274 genotype increased 1000 seed weight, while in k-3358 under the same treatment this parameter was slightly decreased. Statistically significant negative effect of low soil moisture on all estimated parameters in k-3358 genotype and the majority of the estimated parameters in k-8274 genotype was also revealed. Thus, the plants grown in the pot experiment are equivalent to the material grown in the field, and therefore can be used to determine physiological and biochemical markers of functioning of symbiotic systems in order to identify the molecular basis of EIBSM trait. For modeling the pea EIBSM trait in a pot experiments it is recommended to use at least 6 replicas for each genotype. Also, it is necessary to carefully control the soil moisture.