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Dott. Simone Bosco

Phd thesis

 

Integrated approach to sustainable crop protection of rice blast and bakanae: varietal resistance, innovative diagnostics and green control methods.

Rice is one of the most important staple food worldwide, Italy is the biggest rice producer in Europe. The main diseases affecting rice globally are rice blast and bakanae; in Italy, rice blast is the most important in terms of yield loss.

Rice blast, caused by Pyricularia oryzae, is the most severe fungal rice disease and can reduce yields as much as 50% under favorable conditions. The pathogen causes necrotic lesions on leaves, thus reducing the photosynthetical surface area; it also determines panicle sterility when lesions occur at the basal panicular node, and the typical sign is a grey sporulation in the middle of mature lesions. P. oryzae can also infect seeds, which represent a very efficient mode of transmission on long distances, while its intra- and inter-field spread is mainly anemophilous through conidia. Conventional control strategies have been focused on preventive treatments especially during the booting stage, when the plant is most susceptible to panicle blast. However, fungicide resistant strains have been recently detected in Italy, highlighting the necessity of integrated control approaches.

Bakanae is a seedborne rice disease caused by Fusarium fujikuroi, which is widespread in Italy, where the average field incidence is 15%. Typical symptoms include seedling damping off and internode elongation. This disease has become more concerning for seed companies and farmers as most conventional fungicides for seed dressing are gradually phasing out in EU. For this reason, the demand for precise diagnostic methods and efficient control strategies against F. fujikuroi has increased in the last few years.

Endophytes are defined as microorganisms capable of colonizing plant internal tissues, also known as endosphere, without causing disease. Endophytes represent a high potential in biological control applications as their close relationship with the host allows better protection from abiotic stresses. The main disadvantage of microorganisms employed in biological control is their reduced efficiency in field conditions. For this reason using endophytes can determine higher chances of adaptation in harsh environmental conditions.

My PhD project, in collaboration with the seed company Sa.Pi.Se., aims to find innovative green tools to control these threatening diseases for Italian rice cultivation. Three tasks will be carried out:

  • molecular characterization of Italian P. oryzae isolates in order to understand the intraspecific diversity at population level;
  • selection of biocontrol agents against P. oryzae and F. fujikuroi among rice endophytes;
  • surveillance of P. oryzae in rice fields through metagenomic quantification of air inoculum.

 

Research activities

The research activity of this PhD project is divided into three main tasks: 1) rice blast resistance assessment in Italian rice cultivars; 2) biological control of rice pathogens; 3) development of innovative monitoring methods for P. oryzae.

 

Task 1 – Rice blast resistance assessment in Italian rice cultivars.

1A – Collection and molecular characterization of P. oryzae isolates.

Isolation of P. oryzae from Italian rice fields following a monoconidial isolation protocol optimized for slow growing fungi. Sampling in Piedmont and Lombardy, the main Italian rice cultivation areas. Molecular characterization of the isolates based on the presence of effector genes, indicators of the virulence degree of different physiologic races. 

1B – Italian rice cultivars resistance or tolerance to rice blast

Pathogenicity tests on modern and ancient Italian rice cultivars in order to verify the natural presence of resistance or tolerance traits against this pathogen from the local rice germplasm.

 

Task 2 - Biological control of rice pathogens.

2A – Isolation of endophytes from rice seeds and evaluation of their potential biocontrol activity against F. fujikuroi.

Isolation from rice seeds of cultivars resistant to F. fujikuroi. In vivo biocontrol screening through seed treatment under controlled conditions. Molecular identification and in vitro assays to highlight putative biocontrol mode of action of selected strains.

2B - Isolation of endophytes from rice plants and evaluation of their potential biocontrol activity against P. oryzae.

Isolation from rice leaves of cultivars resistant to P. oryzaeIn vivo biocontrol screening through spray treatment of leaves under controlled conditions. Molecular identification and in vitro assays to highlight putative biocontrol mode of action of selected strains.

2C – Field trials with potential biocontrol agents.

Field trials with endophytes that successfully reduced disease symptoms caused by both pathogens at least twice using experimental rice fields owned by Sa.Pi.Se. 

 

Task 3 – P. oryzae monitoring in rice fields by spore sampling and metagenomics to reduce the use of chemical fungicides.

Spore samplers positioning in Sa.Pi.Se. owned rice fields in order to monitor the aerial microbiome and for the quantification of P. oryzae aerial mycobiome. Quantification data validation with already established qPCR and LAMP protocols for P. oryzae in order to verify the efficiency of metagenomic quantification. 

 

Last update: 12/06/2023 16:54
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