The effect of long-term edaphic stress on the characteristics of next generation of spring wheat hybrids seedlings

A new genetic material of spring wheat (15 hybrid populations) developed within the breeding work for aluminum resistance, was studied in the field and laboratory conditions. Studies of F4 hybrids were carried out on soils that differ in the pH level and in the content of mobile aluminum ions. Strong edaphic stress on background 2 (pH = 3.8; Al3+ content = 211 mg/kg of soil) caused a sharp decrease in yield (by 88.2 %) and productivity traits (by 18.5...63.8 %) compared to background 1 (pH = 4.3; Al3+ = 5.4 mg/kg of soil). Laboratory analysis determined the influence of the reproduction conditions of the previous generation on the parameters of the root system of seedlings, their biomass and the root/sprout ratio (RSR index) in the offspring F5. The seeds were germinated in distilled water (control) and an aqueous solution of aluminum sulfate (experiment). It was shown that the weight of seedlings was significantly more strongly influenced by reproduction conditions (an average decrease of 26.1 %) than artificially created stress (a decrease of 2.3...4.7 %). The majority of hybrids showed a significant increase (by 3.9...16.4 %) in laboratory resistance according to the root length index (IDC) as an adaptive response to prolonged edaphic stress. The recommendation is given to take into account the growing conditions of the previous generation, since under their influence the reactions of genotypes by seedling weight, RSR index, as well as correlations between traits can change. The differences of genotypes in the potential level of traits and their stability in different environments were revealed. The hybrid Karabalykskaya 98 x Lutescens 30 differed in the length of the roots, Baganskaya 95 x Gornouralskaya – in the weight of the seedling. The hybrid Baganskaya 95 x Jasna was characterized by the greatest stability according to a set of parameters. Hybrids with potentially longer roots and high seedling mass showed greater sensitivity to changes in environmental conditions. Genotypes with a predominance of the aboveground part in the control were characterized by a more stable "root/sprout" ratio.

Genome evolution of blind subterranean mole rats: Adaptive peripatric versus sympatric speciation

Speciation mechanisms remain controversial. Two speciation models occur in Israeli subterranean mole rats, genusSpalax: a regional speciation cline southward of four peripatric climatic chromosomal species and a local, geologic-edaphic, genic, and sympatric speciation. Here we highlight their genome evolution. The five species were separated into five genetic clusters by single nucleotide polymorphisms, copy number variations (CNVs), repeatome, and methylome in sympatry. The regional interspecific divergence correspond to Pleistocene climatic cycles. Climate warmings caused chromosomal speciation. Triple effective population size,Ne, declines match glacial cold cycles. Adaptive genes evolved under positive selection to underground stresses and to divergent climates, involving interspecies reproductive isolation. Genomic islands evolved mainly due to adaptive evolution involving ancient polymorphisms. Repeatome, including both CNV and LINE1 repetitive elements, separated the five species. Methylation in sympatry identified geologically chalk-basalt species that differentially affect thermoregulation, hypoxia, DNA repair, P53, and other pathways. Genome adaptive evolution highlights climatic and geologic-edaphic stress evolution and the two speciation models, peripatric and sympatric.

Development of acid-resistant winter rye Kiprez variety

The current trend of winter rye breeding for the conditions of northern agriculture is development of aluminum and acid-tolerant cultivars. Studies were carried out in the central zone of the Kirov region in 1991-2019. The complex natural provocative background was used (aluminum ion content 25.5-26.7 mg/100 g of soil at a pH of salt extract 3.6-3.8; annual epiphytotic development of pink snow mold Microdochium nivale (Fr.). Winter-resistant and adaptive cv. Kirovskaya 89 served as the initial material. A rigid natural provocative background made it possible to select the best plants (500 pieces) that were transplanted in spring to an isolated area. Subsequent negative selections, field and laboratory assessments made it possible to create the Kiprez population. During the period of 1995-2013 population reproduction was carried out on a provocative background and 5 cycles of negative selection with simultaneous study in competitive varietal testing on two soil backgrounds. The first selection cycle contributed to an increase in the yield of the new population under conditions of edaphic stress over the original cv. Kirovskaya 89 by 12.6%; the second and third by 19.5 and 29.3%, respectively. Further selection did not show a significant effect. Since 2010, the further improvement of the cv. Kiprez has been carried out using individual-family selection and paired crosses. A multi-year competitive test (2014-2019) showed the advantage of the cv. Kiprez over the standard and the initial cultivar. The average yield increase to the Kirovskaya 89 variety under conditions of slightly acidic soils (pH − 5.3-5.7; Al3+ − 5.0-6.5) was 0.50 t / ha (Kirov) and 0.75 t/ha (Falenki); in the conditions of edaphic stress − 1.91 t / ha (Falenki). A combination of aluminum- and acid tolerance of the cultivar with drought resistance was revealed. In 2014, with a moisture deficit (31% of the norm) in the grain filling and ripening phase, cv. Kiprez exceeded significantly the cv. Falenskaya 4 (standard) by 0.82 tons/ha (19.1%) in a acidic background; initial cv. Kirovskaya 89 - by 1.97 tons/ha (62.7%). Cv. Kiprez is recommended for cultivation on low-fertile soils in harsh hydrothermal conditions of northern agriculture.

Resistance of flax gene pool samples to edaphic stress caused by low acidity

In conditions of vegetative trial carried out against selective backgrounds in 2017-2019 the response of 27 flax samples to a decrease in soil acidity to neutral pHKCl was studied. The scheme of the experiment was as follows: variant I (control) − pHKCl 5.3-5.5, P2O5 − 320-340 mg/kg, K2O − 81-92 mg/kg; variant II − pHKCl 6.2, P2O5 − 312-345 mg/kg, K2O − 84-98 mg/kg. It has been shown that during the «herringbone» phase in the majority of studied flax genotypes against the background of pH 6.2, the symptoms of “physiological oppression” of flax were observed: small spots developed on the upper leaves, the plants stopped growing, the stems thickened, and the tops of severely affected plants died off. As a result, at the beginning of the growing season at plant height of 7-10 cm, most of the samples were severely affected (from 69 to 100 %). The exceptions were varieties of fibre-flax Hermes (France), Vega 2 (Lithuania), Atlant (Russia) and linseed genotypes No. 3896 (Russia) and Norlin (Canada), which had a weak and medium degree of affection (8.3-45.5 %). Moreover, these genotypes showed a high level of both biological (75-90 %) and agronomic (77.3-85.6 %) resistance in the phase of "early yellow ripeness". The identified flax collection samples can be used as sources of resistance to flax «physiological oppression» caused by stressful edaphic factors in a neutral environment. On the basis of the analysis of the main elements of fiber productivity in studied flax genotypes, it has been established that against the background of pH 6.2 the reduce in plant height was from 11.4 to 52.1 % relative to the control, weight of the technical part of the stem − from 7.2 to 83.4 % , fiber mass − from 9.6 to 85.1 %. For the first time, on the basis of hybridological analysis, an assumption was done as to the pres-ence of a strong dominant gene, controlling the resistance to high soil pH values in the Hermes (France) flax variety and the linseed line No. 3896 (Russia).