Evaluating the impact of drought stress in Nure and Tremois barleys (Hordeum vulgare) treated with plant growth promoting rhizobacteria (PGPR) at seedling phase

Barley is the fifth cultivated herbaceous crop in the world, and its important is due to its economic and nutritional value. Climate change is posing a new challenge to barley production. While drought stress was traditionally associated with the flowering and caryopsis filling stages in barley plants, a new form of drought is now emerging in seedling stage. To mitigate the impact of environmental stresses, plant growth promoting rhizobacteria (PGPR) have been proposed to promote nutrient absorption and plant growth with the production of a range of beneficial substances, such as phytohormones, organic acids, and enzymes. The aim of this study was to evaluate the genotype response and the impact of PGPR treatment on two cultivars of barley, Nure (Italian feeding barley, winter habitus) and Tremois (French malting barley, spring habitus) in seedling phase under drought stress. At sowing, the soil was treated with PGPR and after two weeks of control condition two different water regimes were applied on seedlings (control at 25% and stressed at 12% of soil moisture). The results showed that both genotypes exhibited analogous stress response, however the PGPR treatment showed different effects on the two cultivars. Specifically, PGPR treatment increased root dry weight in stress conditions in Nure seedlings (by 36.6%) and increased dry weight in control conditions in Tremois seedlings (by 31.1%). Furthermore, the treatment increased the photosynthesis efficiency (PhiPS2) in Tremois seedlings (by 6.2%) and generally in both cultivars (by 7.6%) under drought stress. These findings suggest that the use of PGPR could be a useful tool for protecting barley seedlings against drought stress in early stages of development. However, further research is needed to fully understand the mechanisms of action to determine the optimal conditions for using this approach in the field

Nitrogen Fertilizers Shape the Composition and Predicted Functions of the Microbiota of Field-Grown Tomato Plants

The microbial communities thriving at the root_soil interface have the potential to improve plant growth and sustainable crop production. Yet, how agricultural practices, such as the application of either mineral or organic nitrogen fertilizers, impact on the composition and functions of these communities remains to be fully elucidated. By deploying a two-pronged 16S rRNA gene sequencing and predictive metagenomics approach, we demonstrated that the bacterial microbiota of field-grown tomato (Solanum lycopersicum) plants is the product of a selective process that progressively differentiates between rhizosphere and root microhabitats. This process initiates as early as plants are in a nursery stage and it is then more marked at late developmental stages, in particular at harvest. This selection acts on both the bacterial relative abundances and phylogenetic assignments, with a bias for the enrichment of members of the phylum Actinobacteria in the root compartment. Digestate-based and mineral-based nitrogen fertilizers trigger a distinct bacterial enrichment in both rhizosphere and root microhabitats. This compositional diversification mirrors a predicted functional diversification of the root-inhabiting communities, manifested predominantly by the differential enrichment of genes associated to ABC transporters and the two-component system. Together, our data suggest that the microbiota thriving at the tomato root_soil interface is modulated by and in responses to the type of nitrogen fertilizer applied to the field

Strategie innovative e rispettose dell’ambiente per la produzione del pomodoro da industria (Solanum lycopersicum L.)

Il pomodoro da industria è un coltura economicamente importante a livello mondiale e la sua resa e la qualità sono strettamente legati all’ uso dei fertilizzanti. Infatti, la resa del pomodoro da industria è inferiore nei sistemi biologici rispetto a quelli convenzionali. Inoltre, la maggior parte dei genotipi coltivati sono sensibili, in tutti gli stadi di sviluppo, alle basse temperature ed estremamente dipendenti all’ irrigazione. In quest’ottica, lo scopo del presente progetto di dottorato è stato quello di migliorare la tolleranza agli stress abiotici e aumentare la produzione sostenibile del pomodoro da industria sfruttando la biodiversità delle specie e l’effetto positivo dei microorganismi del suolo. Focalizzando l’attenzione sugli stress abiotici che limitano la crescita delle piantine del pomodoro da industria, abbiamo valutato l’effetto e le interazioni tra microrganismi benefici (Funneliformis mosseae, Rhizophagus intraradices and Paraburkholderia graminis) e diversi genotipi di pomodoro da industria (‘Pearson’, ‘H3402’ and ‘Everton’) sottoposti a stress idrico e termico (capitoli tre e quattro). I nostri risultati mostrano che F. mosseae è stato più efficace a ridurre i danni dovuti all’ esposizione delle piantine alle basse temperature e a mitigare gli effetti della siccità a livello fisiologico e morfologico. Inoltre, ci sono state diverse interazioni significative tra genotipi, microrganismi e stress. Inoltre, è stato studiato l’uso di portainnesti (‘RS01658654’ and ‘Tomito’) inoculati o meno con microrganismi benefici ( da solo o in consorzio) (Funneliformis mosseae, Paraburkholderia graminis and Azospirillum brasiliensis) al fine di incrementare la resa commerciale e la qualità dei frutti in sistemi biologici (capitoli cinque e sei). È interessante notare che ‘H3402’ innestato su ‘Tomito’ ed inoculato con A. brasiliensis ha avuto, in serra, una fioritura precoce, mentre in campo, lo stesso innesto inoculato con alcuni microrganismi benefici (P. graminis, A. brasiliensis ed il loro consorzio) ha mostrato un aumento della resa commerciale, della qualità dei frutti ed una riduzione del numero di frutti affetti da marciume apicale. Infine, abbiamo ipotizzato che le differenti performance del pomodoro da industria, associate all’ utilizzo di forme diverse di azoto, fossero determinate, almeno in parte, da un differente reclutamento di batteri all’ interfaccia radice-suolo. Per valutare quest’ipotesi, un singolo genotipo è stato coltivato in campo e soggetto a sette diversi tipi di trattamenti fertilizzanti (stessa quantità di azoto) (capitolo sette). Usando un protocollo indipendente dalla coltura, è stata valutata la resa, la qualità e la composizione del microbiota dimostrando che ogni trattamento è in grado di produrre delle caratteristiche distintive, rappresentate dall’ arricchimento di specifici microorganismi delle comunità microbica della radice e della rizosfera. In questo lavoro, sono state fornite prove sull’ efficacia dell’uso di microrganismi benefici e dell’innesto per migliorare la resa e la qualità del pomodoro da industria. Tuttavia le interazioni tra specifici microrganismi benefici, genotipi e sistemi di coltivazione dovrebbero essere considerate per produrre biostimolanti ad hoc. Inoltre, tutti gli approcci presentati potrebbero essere la chiave per migliorare la gestione della fertilizzazione e dell’acqua di irrigazione per aumentare la resa e la qualità dei frutti e anticipare l’efficace sfruttamento del microbiota delle piante per fini agricoli.Processing tomato is a worldwide economic important crop and his yield and quality are strictly affected by fertilizer applications. In fact, the processing tomato yield is lower in organic systems in comparison with conventional ones. In addition, most cultivated genotypes are sensitive to chilling in all growth stages and extremely dependent on irrigation water. In this view, the present PhD project aimed to increase the tolerance to abiotic stresses and the sustainable production of processing tomato exploiting the biodiversity of the species and the beneficial effect of the soil microbiota. Focusing on the abiotic stresses that limit processing tomato growth at seedlings stage, we evaluated the effects and the interactions between beneficial microorganisms (Funneliformis mosseae, Rhizophagus intraradices and Paraburkholderia graminis) and processing tomato genotypes (‘Pearson’, ‘H3402’ and ‘Everton’) under chilling or drought stresses (chapters three and four). Our results showed that F. mosseae was the most effective in reducing the chilling damage and in mitigating the effects of drought on morphological and physiological traits. In addition, specific genotype x microbiota x stress interactions were also revealed. The use of rootstocks (‘RS01658654’ and ‘Tomito’) in combination with or without beneficial microorganisms (alone and in consortia) (Funneliformis mosseae, Paraburkholderia graminis and Azospirillum brasiliensis) were studied in order to improve marketable yield and quality under organic cropping system (chapters five and six). Interestingly, ‘H3402’ grafted onto ‘Tomito’ and inoculated with A. brasiliensis was early flowering in greenhouse, while in the field grafting plus beneficial microorganisms (P. graminis, A. brasiliensis and their consortium) increased marketable yield, fruit quality and reduced the number of fruits affected by blossom-end rot. Finally, we hypothesized that differences in processing tomato performances associated to different forms of nitrogen could be determined, at least in part, by a differential recruitment of bacteria at the root-soil interface. To test this hypothesis, a single genotype was grown in open field subjected to seven fertilizer treatments (same amount of N) (chapter seven). Using a cultivation-independent protocol we assessed crop yield, quality and microbiota composition demonstrating that each treatment produced “distinct signatures”, represented by specific selective enrichment on both the rhizosphere and root community. In our results, we provide evidence for the use beneficial microorganisms and grafting to improve adaptation, yield and quality of processing tomato. However, specific beneficial microorganisms x genotype/cropping system interactions should be considered to produce ad hoc biostimulants. All the presented approaches could be a key strategy towards improved fertilization and irrigation water managements to increase fruit yield and quality, and we foresee an effective exploitation of the plant microbiota for agricultural purposes

Characterization of Leaf Transcriptome of Grafted Tomato Seedlings after Rhizospheric Inoculation with Azospirillum baldaniorum or Paraburkholderia graminis

Inoculation with plant growth promoting rhizobacteria (PGPR) might be a sustainable practice to increase nutrients use efficiency of crops. In order to elucidate the mechanisms underlying the beneficial interaction, an RNA-Seq transcriptional profiling of tomato leaves was performed after roots’ inoculation with Azospirillum baldaniorum (AB) or Paraburkholderia graminis (PG). Overall, 427 and 512 differentially expressed tomato genes were retrieved for AB and PB inoculation, respectively, and in both cases, the number of up-regulated genes exceeded the number of those down-regulated. Expression profiles suggest that the interactions between tomato seedlings and microorganisms are species-specific. The common activated pathways involved genes coding for proteins related to water and nutrients uptake, defense responses to biotic and abiotic stresses and hormonal regulation of fruit-set and ripening. While AB induced genes coding for MYB transcription factors known to be involved in response to biotic and abiotic stresses, PG upregulated 5 genes coding for putative late blight resistance protein homolog. Auxin responsive molecules and gibberellins involved in the fruit-set and early fruit growth in tomato were mainly induced by AB correlating to higher fruit number obtained in a previous field study. On the other hand, ERF transcription factors involved in ripening were induced mainly by PG treatment

Grafting and Plant Density Influence Tomato Production in Organic Farming System

The tomato is a key crop cultivated worldwide for the fresh and processing markets. Only a small percentage of the tomatoes processed by industries were produced following the guidelines of the organic farming system. Potential reasons for the limited share of organic tomato production are probably related to the lower yield obtained in organic farming in comparison with conventional farming. In this study, the use of the cherry tomato genotype ‘Tomito’ as a rootstock and two different plant densities (2.5 and 1.25 plant m−2) were evaluated in order to improve the agronomic performances of the commercial processing tomato genotype ‘H3402′ cultivated in the organic farming system. Agronomic and quality parameters were assessed at harvest time. The plant density influenced the plant biometric parameters, mass and marketable yield, and fruit health and quality. The use of a rootstock improved the marketable yield per plant (more than 59%), with the quality of the fruit decreasing the number of sunburnt fruits (−27.7%). The use of the ‘Tomito’ as a rootstock and a plant density of 2.5 plant m−2 are the better choices to achieve good performances in optimal environmental conditions. However, further studies are required to validate these results both in other environments and using different scions

The <i>Triticeae CBF</i> Gene Cluster—To Frost Resistance and Beyond

The pivotal role of CBF/DREB1 transcriptional factors in Triticeae crops involved in the abiotic stress response has been highlighted. The CBFs represent an important hub in the ICE-CBF-COR pathway, which is one of the most relevant mechanisms capable of activating the adaptive response to cold and drought in wheat, barley, and rye. Understanding the intricate mechanisms and regulation of the cluster of CBF genes harbored by the homoeologous chromosome group 5 entails significant potential for the genetic improvement of small grain cereals. Triticeae crops seem to share common mechanisms characterized, however, by some peculiar aspects of the response to stress, highlighting a combined landscape of single-nucleotide variants and copy number variation involving CBF members of subgroup IV. Moreover, while chromosome 5 ploidy appears to confer species-specific levels of resistance, an important involvement of the ICE factor might explain the greater tolerance of rye. By unraveling the genetic basis of abiotic stress tolerance, researchers can develop resilient varieties better equipped to withstand extreme environmental conditions. Hence, advancing our knowledge of CBFs and their interactions represents a promising avenue for improving crop resilience and food security

The Triticeae CBF Gene Cluster—To Frost Resistance and Beyond

The pivotal role of CBF/DREB1 transcriptional factors in Triticeae crops involved in the abiotic stress response has been highlighted. The CBFs represent an important hub in the ICE-CBF-COR pathway, which is one of the most relevant mechanisms capable of activating the adaptive response to cold and drought in wheat, barley, and rye. Understanding the intricate mechanisms and regulation of the cluster of CBF genes harbored by the homoeologous chromosome group 5 entails significant potential for the genetic improvement of small grain cereals. Triticeae crops seem to share common mechanisms characterized, however, by some peculiar aspects of the response to stress, highlighting a combined landscape of single-nucleotide variants and copy number variation involving CBF members of subgroup IV. Moreover, while chromosome 5 ploidy appears to confer species-specific levels of resistance, an important involvement of the ICE factor might explain the greater tolerance of rye. By unraveling the genetic basis of abiotic stress tolerance, researchers can develop resilient varieties better equipped to withstand extreme environmental conditions. Hence, advancing our knowledge of CBFs and their interactions represents a promising avenue for improving crop resilience and food security

Digestato solido compostato per la propagazione della vite

La ricerca, che si inserisce nel progetto VADISAVI (VAlorizzazione del DIgestato e dei SArmenti di Vite), finanziato dal Dipartimento di Scienze della Vita sui Fondi di Ateneo per la Ricerca (FAR 2015), si è posto l’obiettivo di valutare un nuovo substrato di coltivazione a base di digestato compostato con sarmenti per la produzione e l’allevamento di viti in vaso nei primi anni di crescita.. L’individuazione di substrati innovativi, in sostituzione della torba, rappresenta un fattore fondamentale per la strutturazione di economie circolari, in quanto consente un recupero dei sottoprodotti delle filiere agricole e agroalimentari, valorizzandoli, e la riduzione del consumo di una risorsa non rinnovabile e ormai disponibile in quantità limitate. Sono stati quindi testati tre substrati nei quali parte della torba è stata sostituita con diverse percentuali di compost (10, 20 e 40%), a confronto con substrati costituiti di sola torba (100%) e torba fertilizzata, comunemente utilizzati nel vivaismo viticolo. I nuovi substrati non hanno determinato problemi di carenze o di fitotossicità. La tesi 100% torba + fertilizzante ha mostrato i valori più elevati di indici di clorofilla (valore SPAD e Chl) e NBI e di altezza delle piante. Tuttavia, anche tutti i substrati in cui la torba è stata parzialmente sostituita hanno dato risultati soddisfacenti con tutte le tipologie di materiali vegetali testati: barbatelle, innesti-talea radicata, piante di due anni