Introduction: Botrytis cinerea is one of the pathogenic fungi causing major problems worldwide in crops such as tomato. Some Plant Growth-Promoting Rhizobacteria (PGPR) can activate induced systemic resistance (ISR) pathways in crops, reducing the need for antifungals.Methods: Three strains belonging to the species Peribacillus frigoritolerans (CD_FICOS_02), Pseudomonas canadensis (CD_FICOS_03), and Azotobacter chroococcum (CD_FICOS_04), which exhibit outstanding PGPR properties, were evaluated for their ability to protect tomato plants against B. cinerea infection by ISR via soil inoculation.Results: The strains CD_FICOS_02 and CD_FICOS_03 reduced B. cinerea incidence and plant oxidative stress. The first strain mainly increased the expression of genes related to the salicylic acid pathway, while the second increased the expression of genes related to the jasmonic acid/ethylene hormonal pathway, indicating preferential ISR activation by each of these pathways. In addition, CD_FICOS_03 was able to increase the root and aerial biomass production of infected plants compared to the control. Interestingly, although the strain CD_FICOS_04 did not reduce the damage caused by B. cinerea, it increased the biomass of infected plants.Discussion: Our results suggest that the best strategy for biocontrol of B. cinerea is to combine the ability to promote plant growth with the ability to induce systemic resistance, as demonstrated by strains P. frigoritolerans CD_FICOS_02 and P. canadensis CD_FICOS_03.

Background: Rice straw, often treated as waste, provides many benefits to crops when used as a mulch. However, straw degradation promotes nitrogen immobilisation due to its high C:N ratio, causing N competition between soil microorganisms and the crop. Currently, sustainable practices to remedy nitrogen immobilisation are hardly being implemented. In microcosm conditions we assessed whether the inoculation with N-fixers could offset the transient nitrogen deficiency caused by straw mulch, thereby harnessing the benefits of straw while mitigating its negative impact on nitrogen depletion and exerting a synergistic effect on crop growth. Results: Inoculation with N-fixers increased the nitrogen content in the soil (the increase ranged from 14% up to 90% for NH₄⁺ and from 20% to 60% for NO₃⁻) and, in most cases, also the nitrogen content in the plant (ranging from 10% to 15% increase), compared to the non-inoculated control. Therefore, inoculation would compensate for the lack of nitrogen caused by nitrogen immobilisation, and this resulted in an increased biomass production by the crop compared with the uninoculated control (the increase ranged from 25% to 85%). In addition, inoculation with N-fixers did not lead to a permanent change in the bacterial community composition, whereas straw addition increased the biodiversity of the soil microbiome. Conclusions: The results obtained in microcosm conditions are a first indication that complementing straw mulching with the inoculation of N-fixers could avoid the transient N immobilisation produced during straw degradation. Thus, the benefits of the combination would be a yield increase, while improving the biodiversity of the soil microbiome, stabilising soil temperatures and increasing water soil content. Graphical

Pollen grains show an enormous variety of aperture systems. What genes are involved in the aperture formation pathway and how conserved this pathway is in angiosperms remains largely unknown. INAPERTURATE POLLEN1 (INP1) encodes a protein of unknown function, essential for aperture formation in Arabidopsis, rice and maize. Yet, because INP1 sequences are quite divergent, it is unclear if their function is conserved across angiosperms. Here, we conducted a functional study of the INP1 ortholog from the basal eudicot Eschscholzia californica (EcINP1) using expression analyses, virus-induced gene silencing, pollen germination assay, and transcriptomics. We found that EcINP1 expression peaks at the tetrad stage of pollen development, consistent with its role in aperture formation, which occurs at that stage, and showed, via gene silencing, that the role of INP1 as an important aperture factor extends to basal eudicots. Using germination assays, we demonstrated that, in Eschscholzia, apertures are dispensable for pollen germination. Our comparative transcriptome analysis of wild-type and silenced plants identified over 900 differentially expressed genes, many of them potential candidates for the aperture pathway. Our study substantiates the importance of INP1 homologs for aperture formation across angiosperms and opens up new avenues for functional studies of other aperture candidate genes.

Treated bio-residues can be used as biostimulants in crops within the circular economy approach to reduce the use of traditional fertilisers. In this work, we optimised the combination rates for three types of treated bio-residues (compost, biochar, and anaerobic digestate (AD)) in two microcosm trials, one with a combination of compost and biochar and other with biochar and AD. The crop used was maize, and the variables analysed were plant growth, and soil chemical and biological properties. The combination of bio-residues improved plant growth and soil biological activity to a greater extent than one product alone; that is, compost and biochar performed better than compost alone and biochar, and AD performed better than biochar alone. However, while the concentration in the plant biomass of several essential nutrients for crops increased in the treatments with compost and biochar, and with biochar and AD, compared to the untreated controls, the nitrogen concentration was reduced. This was due to the competition for nitrogen between the plant and the soil microbiome, whose activity was activated. Due to the importance of nitrogen in plant growth, the increase in biomass production could be explained not only by the higher availability of other nutrients but also by the plant-growth-promoting activity exerted by the more active soil microbiome. Further research should focus on validating this hypothesis and unravelling the mechanisms involved. From the environmental site, the presence of biochar in the mixtures of organic residues reduced the soil nitrogen at risk of lixiviation and sequestered carbon, which partially compensated for the increased CO₂ emissions because labile forms of carbon were present in the remaining organic residues.

In the last decade, certain genes involved in pollen aperture formation have been discovered. However, those involved in pollen aperture shape remain largely unknown. In Arabidopsis, the interaction during the tetrad development stage of one member of the ELMOD protein family, ELMOD_E, with two others, MCR/ELMOD_B and ELMOD_A, can change the morphology of apertures from colpus (elongated) to pore (round). Here, comparative transcriptome analysis is used to identify candidate genes involved in the determination of pollen aperture morphology in Papaveraceae (order Ranunculales). Furthermore, the role of ELMOD genes in the genetic determinism of aperture shape was tested by comparative analysis of their expression levels using RNA-seq data and RT-qPCR. Two pairs of species belonging to two different subfamilies were used. Within each pair, one species has colpate pollen and the other porate (Fumarioideae—Dactylicapnos torulosa, 6-colpate, and Fumaria bracteosa, pantoporate; Papaveroideae—Eschsholzia californica, 5–7 colpate, and Roemeria refracta, 6-porate). The transcriptomes were obtained at the tetrad stage of pollen development. A total of 531 DEGs were found between the colpate and porate pollen species groups. The results from RNA-seq and RT-qPCR indicate that pollen aperture shape is not determined by the relative expression levels of ELMOD family genes in Papaveraceae. However, genes related to callose wall formation or cytoskeleton organisation were found, these processes being involved in pollen aperture formation. In addition, transcriptomes from anthers with pollen during the tetrad stage of three species (D. torulosa, R. refracta, and F. bracteosa) were obtained for the first time. These data will be available for further studies in the field of floral evolution and development.

One of the main abiotic stresses that threaten the survival of wheat ( Triticum spp.) is drought. The present work aims to evaluate the ability of different plant growth promoting microorganisms (PGPMs) to alleviate the effects of dehydration in wheat and to understand the mechanisms involved. Wheat seeds ( Triticum aestivum L. ssp. cv. ‘ Galera’ ) inoculated with the strains Priestia megaterium CD_FICOS_01, Peribacillus frigoritolerans CD_FICOS_02, Pseudomonas canadensis CD_FICOS_03, Azotobacter chroococcum CD_FICOS_04 or Pichia kluyveri CD_FICOS_05 were exposed to prolonged drought by water shortage after which agronomic parameters, biochemical markers of abiotic stress and expression of genes related to plant response to water stress were measured. The behaviour of the PGPM strains evaluated varied in alleviating plant water stress, allowing two groups to be differentiated. The application of strains CD_FICOS_01, CD_FICOS_02 and CD_FICOS_03 resulted in an enhancement of crop production, with increases in aerial fresh biomass of 59%, 18%, and 38%, respectively, compared to the control. These strains also stimulated ethylene and/or abscisic acid metabolism. In contrast, strains CD_FICOS_04 and CD_FICOS_05 were also able to promote mechanisms related to the plant response to abiotic stress (MDA, proline, H ₂ O ₂ ), but did not exert any physiological effect at plant level. In fact, they reduced the yield, with decreases in aerial fresh biomass of 43% and 21%, and in aerial dry biomass of 33% and 20%, respectively.