Soil salinity is one of the abiotic stress factors gaining importance in recent years due to the changing climate and rising temperatures. This possesses a serious risk to food security worldwide and a range of adaptations and mitigation strategies are required. Crop improvement through breeding is a possible solution to overcome salinity stress. In this respect, a study was designed to screen a collection from garden pea accessions to salinity tolerance in in vitro conditions. We analyzed the effects of four salinity levels (0, 50, 100, and 200 mM NaCl) on seed germination, seedling emergence, shoot and root lengths, and plant fresh weight in 22 garden pea genotypes. Data showed that more of the pea genotypes are able to tolerate 50 mM NaCl concentration. The increasing of salt levels to 100 and 200 mM NaCl caused a significant decrease in germination and reduced the length and weight of shoots and roots. Among the genotypes, varieties Uspeh 72, Paldin, and Flora 6 were highly sensitive to salinity stress, while varieties Prometey, Musala, and Zornitsa were distinguished as more tolerant. The results depicted that salinity treatments had a more negative effect on plant growth than on seed germination, which is probably due to the in vitro conditions in which the experiments were conducted. The studied accessions of garden pea were sensitive to salt stress; nevertheless, some tolerant accessions were identified.

Changes in morphological characteristics, productivity and fluorescence emission parameters at normal and high temperature values under field conditions of 10 varieties and lines of the species Pisum sativum L. from the collection of MARITSA Vegetable Crops Research Institute were established. The influence of high temperature on the condition and functional activity of the photosynthetic apparatus (PSA) was studied by analyses of chlorophyll fluorescence characteristics of photosystem II (PSII) in the pea leaves. Plants were subjected to stress from high temperature during the reproductive period (bud formation - flowering phases), which is considered particularly critical for pea plants. The morphological performances and productivity have been influenced by climatic characteristics of the years. The screening for thermostability of the photosynthetic apparatus to the high temperature characterizes Skinado, Faboundo and line 95/4 as the most tolerant on the basis of analysis of fluorescence induction parameters. The most sensitive are lines 72/2 and 72/9. Varieties of Skinado and Fabundo respond with higher yields of green pods and grains in the conditions of the first year, categorized as hot compared to 2013. We consider that the indicated accessions are suitable for the pea-breeding programme to high temperature stress tolerance.

The present research study identified garden pea varieties with pronounced tolerance to the allelopatic action of Sorghum halepense. Nine varieties were selected to study the effects of shoot and root weed biomass, applied in three extract concentrations (1, 5 and 10%), on seed germination and initial germ growth. A variance analysis of data revealed significant influence (p <0.05) of three studied factors (variety, type and concentration of extracts) on the investigated parameters. Statistically insignificant was only the influence of extract type (root/aboveground biomass) on seed germination. Based on absolute values of the allelopathic indicator RI, which determines the degree of allelopathic inhibition in terms of germination, germ length and weight in different varieties, the variation was as follows: from -0.30 to -0.04, from -1.31 to -2.96 and from -0.47 to 0.02. The total effect of allelopathic action of S. halepense on all studied parameters, presented as a GGE-biplot analysis, defined Pulpudeva and Puldin varieties as exhibiting higher tolerance, in contrast to Denitsa and Vyatovo, which were sensitive. Ran I, Mira, Musala and Vechernitsa occupied an intermediate position. Cultivation of allelopathic tolerant varieties is a promising addition to the current weed control strategy, especially in organic production.

This study of a legume’s rhizosphere in tripartite symbiosis focused on the relationships between the symbionts and less on the overall rhizosphere microbiome. We used an experimental model with different garden pea genotypes inoculated with AM fungi (Rhizophagus irregularis and with a mix of AM species) to study their influence on the population levels of main trophic groups of soil microorganisms as well as their structure and functional relationships in the rhizosphere microbial community. The experiments were carried out at two phenological cycles of the plants. Analyzes were performed according to classical methods: microbial population density defined as CUF/g a.d.s. and root colonization rate with AMF (%). We found a proven dominant effect of AMF on the densities of micromycetes and actinomycetes in the direction of reduction, suggesting antagonism, and on ammonifying, phosphate-solubilizing and free-living diazotrophic Azotobacter bacteria in the direction of stimulation, an indicator of mutualistic relationships. We determined that the genotype was decisive for the formation of populations of bacteria immobilizing mineral NH₄⁺-N and bacteria Rhizobium. We reported significant two-way relationships between trophic groups related associated with soil nitrogen and phosphorus ions availability. The preserved proportions between trophic groups in the microbial communities were indicative of structural and functional stability.

Among factors affecting snap bean production in organic growing systems, pests and diseases are of paramount importance. The current study was aimed to determine the impact of organic production practices on snap bean pests and diseases infestation, soil fertility and yield. Five treatments of plants during the whole growing season with a Bordeaux mixture at a dose of 3000 g/ha, provided more than 50 percent protective effect against the development of the bacterial blight Xanthomonas axanopodis pv. phaseoli and anthracnose Colletotrichum lindemuthianum. In organic fields, commercial bioproducts containing pyrethrins or entomopathogenic fungi Beauveria bassiana can be successfully applied to control the black bean aphid (Aphis fabae Scop.). To limit the attack of bean weevil (Acanthoscelides obtectus Say), phytopesticide containing pyrethrins can also be used. Against the two-spotted spider mite (Tetranychus urticae Koch.), products containing the active ingredient azadirachtin were seen to be effective five days after treatment. Soil amendment with vermicompost at a dose of 2850 L/ha slightly increased the amounts of water-soluble nutrients; however, soil remained nutrient deficient across the growing season. Among the tested Bulgarian varieties, Evros possessed higher yield, and appear to be suitable for organic system than the Tangra variety.