Silicon supplied via foliar application and root to attenuate potassium deficiency in common bean plants

Potassium (K) deficiency affects physiological performance and decreases vegetative growth in common bean plants. Although silicon (Si) supplied via nutrient solution or foliar application may alleviate nutritional stress, research on the bean crop is incipient. Thus, two experiments were carried out: initially, a test was performed to determine the best source and foliar concentration of silicon. Subsequently, the chosen Si source was supplied in nutrient solution via roots or foliar application to verify whether Si supply forms are efficient in alleviating the effects of K deficiency. For these purposes, a completely randomized 2 × 3 factorial design was used, with two levels of K: deficient (0.2 mmol L−1 of K) and sufficient (6 mmol L−1 of K); and Si: in nutrient solution via roots (2 mmol L−1 of Si) or foliar application (5.4 mmol L−1 of Si) and control (0 mmol L−1 of Si). Our findings revealed that Si supplied via foliar spraying using the source of sodium silicate and stabilized potassium at a concentration of 5.4 mmol L−1 was agronomically viable for the cultivation of bean plant. K deficiency, when not supplied with silicon, compromised plant growth. Moreover, root-and-foliar-applied Si attenuated the effects of K deficiency as it increased chlorophylls and carotenoids content, photosynthetic activity, water use efficiency and vegetative growth. For the first time, the role of Si to mitigate K deficiency in the bean crop was evidenced, with a view to further research on plants that do not accumulate this beneficial element.

Impacts of Rhizobium Strain Ar02 on the Nodulation, Growth, Nitrogen (N2) Fixation Rate and ion Accumulation in Phaseolus vulgaris L. under Salt Stress

Background: Phaseolus vulgaris L. -rhizobia symbiosis has effectively enhanced common bean productivity via multiple biological mechanisms. This study aims to assess the impacts of the strain of Rhizobium on the nodulation, growth, nitrogen (N2) fixation rate and ion accumulation within Phaseolus vulgaris L. under salt stress. Methods: The Coco Blanc cultivar of the common bean was inoculated with the Ar02 rhizobia strain at 15 days after germination. Bean plants were inoculated in perlite culture to which salt was added in concentrations of 0, 25, 50 and 75 mmol L-1 NaCl. Result: Inoculation with the Ar02 rhizobia strain led to infective and effective symbiosis with the common bean plants exposed to saline solutions and non-saline solutions, respectively. Nodule biomass and nitrogen content declined under salt stress but maintained a higher number of nodules and nodule biomass at 75 mM NaCl. Plant root and shoot length increased with higher biomass under saline conditions, significantly more than the non-inoculated plant without salt. However, the progressive addition of NaCl reduced the growth of the root and shoot and the biomass within the inoculated plant. Salinity led to increased Na+ within the plant’s shoot, along with a reduction in Ca+2 and K+ concentrations. The shoot’s Ca+2, Na+ and K+ content were higher in the inoculated plant than the non-inoculated. The salt tolerance in common bean plants inoculated with Ar02 rhizobia was linked with the plant’s capability to sustain nodulation and enhance Na+ concentration in the shoot. Furthermore, salt tolerance within the same variety inoculated with Rhizobium was linked to a decline in the Ca+ and K+ concentrations in the shoot region of salt-exposed plants.

Early nitrogen supplementation stimulates the nodulation and growth of common bean plants inoculated with rhizobium

The initial development of common bean plants (Phaseolus vulgaris L.) relying on symbiotic nitrogen (N) can be limited by delayed active N2 fixation, requiring supplemental N which in turn may inhibit the symbiosis. Five experiments were carried out in hydroponics to identify the initiation of nodulation and nitrogenase activity in common bean cultivars, and the effects of additions of mineral N on plant nodulation and growth. Three experiments evaluated the initial growth of five inoculated bean cultivars in the absence or presence of mineral N, and two experiments evaluated the effect of the moment of mineral N addition until the beginning of reproductive stage. The first root nodules appeared 10 days after plant transplant (DAT) and nitrogenase activity initiated 11 DAT. Cultivars of large seeds had lower initial nodulation and nitrogenase activity than those of small seeds. Inoculated plants showed limited shoot growth that lasted until 21-25 DAT as compared to inoculated plants receiving mineral N. Addition of mineral N reduced nodule mass more intensively than nodule number and more strongly nitrogenase activity. Nitrogen applied until 15 DAT enhanced nodulation and nitrogenase activity without limiting shoot growth, as compared to plants receiving N throughout their growth. Otherwise, plants that received N after 15 DAT had lower nodule mass and nitrogenase activity than plants only inoculated. The results indicate that symbiotic N did not suffice to an adequate growth of common beans and some supplemental N is necessary. This N should be added in the beginning of growth cycle to stimulate plant growth without inhibiting further nodulation and N fixation.

Indigenous rhizobial strains SEMIA 4108 and SEMIA 4107 for common bean inoculation: A biotechnological tool for cleaner and more sustainable agriculture

Summary Inoculation of symbiotic N2-fixing rhizobacteria (rhizobia) in legumes is an alternative to reduce synthetic N fertiliser input to crops. Even though common bean benefits from the biological N2 fixation carried out by native rhizobia isolates, the low efficiency of this process highlights the importance of screening new strains for plant inoculation. Two rhizobial strains (SEMIA 4108 and SEMIA 4107) previously showed great potential to improve the growth of common beans under greenhouse conditions. Thus, this study evaluated the growth and grain yield of common bean plants inoculated with those strains in field experiments. The rhizobial identification was performed by 16S rRNA sequencing and the phylogeny showed that SEMIA 4108 and SEMIA 4107 are closely related to Rhizobium phaseoli, within a clade containing other 18 Rhizobium spp. type strains. Common bean plants inoculated with SEMIA 4107 showed similar productivity to N-fertilised (N+) plants in the first experiment (2016/17) and higher productivity in the second experiment (2018/19). The development of inoculated plants was different from that observed for N+. Nonetheless, comparing inoculated treatments with N-fertilised control, no yield or productivity losses at the end of the growing process were detected. Our results showed that inoculation of the rhizobial isolates SEMIA 4108 and SEMIA 4107 improved the growth and grain yield of common bean plants. The observed agronomical performance confirms that both strains were effective and can sustain common bean growth without nitrogen fertilisation under the edaphoclimatic conditions of this study.

COBALT COMPLEXONES BASED ON ENVIRONMENTALLY FRIENDLY COMPLEXONS AS MICRO-ELEMENT FERTILIZERS

Представлены результаты эксперимента по применению созданных хелатных ростостимуляторов на основе экологически безопасных комплексонов для отдельных классов растений. В условиях мелкоделяночного полевого опыта исследовано влияние иминодиянтарной кислоты (ИДЯК), этилендиаминтетрауксусной кислоты (ЭДТУК), хелатных соединений кобальта (II) на их основе: Со-ИДЯК и Со-ЭДТУК, соответственно, на растения фасоли обыкновенной. Обнаружено увеличение содержания хлорофилла и общей массы семян под воздействием ИДЯК и Со-ИДЯК. Из использованных кобальтовых микроудобрений наиболее эффективным оказался комплекс Со-ИДЯК. The results of an experiment on the use of created chelated growth stimulants based on environmentally friendly complexones for certain classes of plants are presented. Under the conditions of a small-plot field experiment, the effect of iminodisuccinic acid (IDS), ethylenediaminetetraacetic acid (EDTA), and chelate compounds of cobalt (II) based on them: Co-IDS and Co-EDTA, respectively, on common bean plants was studied. An increase in the content of chlorophyll and the total mass of seeds was found under the influence of IDS and Co-IDS. Of the cobalt micronutrient fertilizers used, the Co-IDS complex turned out to be the most effective.

Physiological and agronomic characteristics of the common bean as affected by multifunctional microorganisms

Multifunctional microorganisms (MMs) can have beneficial effects on plants through direct and indirect mechanisms. This study aimed to determine the effect of MMs on shoot and root biomass production; gas exchange; content of macronutrients in the shoots, roots and grains; yield components; and grain yield of common bean plants. A completely randomized design with twenty-six treatments and three replications was used under controlled conditions. Treatments consisted of the application of MMs and their combinations in pairs, with the nine rhizobacteria isolates BRM 32109, BRM 32110 and 1301 (Bacillus sp.), BRM 32111 and BRM 32112 (Pseudomonas sp.), BRM 32113 (Burkholderia sp.), BRM 32114 (Serratia sp.), 1381 (Azospirillum sp.) and Ab-V5 (Azospirillum brasilense); an edaphic fungal isolate T-26 (Trichoderma koningiopsis); and a control (without MMs). These MMs were applied at three time points: microbiolization of the seeds, watering the soil seven days after sowing (DAS) and spraying the plants with 21 DAS. In comparison to the control plants, the isolates 1301 and T-26, in addition to the combinations Ab-V5 + T-26, BRM 32114 + BRM 32110 and 1381 + T-26, provided better results, with an increase of 36.5% in the grain yield, a higher accumulation of biomass (78.0%) and a higher content of N, P and K (42.6, 67.8 and 25.7%, respectively) in the shoots of common bean plants. Therefore, the results allow us to infer that the use of MMs is a good strategy for increasing common bean grain yields.

Next-Generation Sequencing-Based Detection of Common Bean Viruses in Wild Plants from Tanzania and Their Mechanical Transmission to Common Bean Plants

Viral diseases are a major threat for common bean production. In recent surveys, >15 different viruses belonging to 11 genera were shown to infect common bean (Phaseolus vulgaris L.) in Tanzania. Management of viruses requires an understanding of how they survive from one season to the next. In this study, we explored the possibility that alternative host plants have a central role in the survival of common bean viruses. We used next-generation sequencing (NGS) techniques to sequence virus-derived small interfering RNAs, together with conventional reverse transcription-polymerase chain reaction (RT-PCR) to detect viruses in wild plants. Leaf samples for RNA extraction and NGS were collected from 1,430 wild plants around and within common bean fields in four agricultural zones in Tanzania. At least partial genome sequences of viruses potentially belonging to 25 genera were detected. The greatest virus diversity was detected in the eastern and northern zones, whereas wild plants in the Lake zone and especially in the southern highlands zone showed only a few viruses. RT-PCR analysis of all the collected plant samples confirmed the presence of yam bean mosaic virus and peanut mottle virus in wild legume plants. Of all viruses detected, only two viruses, cucumber mosaic virus and a novel bromovirus related to cowpea chlorotic mottle virus and brome mosaic virus, were mechanically transmitted from wild plants to common bean plants. The data generated in this study are crucial for development of viral disease management strategies and predicting crop viral disease outbreaks in different agricultural regions in Tanzania and beyond.