Wheat blast: from its origins in South America to its emergence as a global threat.

Wheat blast was first reported in Brazil in 1985. It spread rapidly across the wheat cropping areas of Brazil to become the most important biotic constraint on wheat production in the region. The alarming appearance of wheat blast in Bangladesh in 2016 greatly increased the urgency to understand this disease, including its causes and consequences. Here, we summarize the current state of knowledge of wheat blast and aim to identify the most important gaps in our understanding of the disease. We also propose a research agenda that aims to improve the management of wheat blast and limit its threat to global wheat production.

Chitosan nanoparticle induced defense responses in fingermillet plants against blast disease caused by Pyricularia grisea (Cke.) Sacc.

The in vitro antifungal properties of chitosan nanoparticle and its role in protection of fingermillet plants from blast disease were evaluated. Chitosan nanoparticle inhibited the radial growth of Pyricularia grisea indicating the antifungal property. Application of chitosan nanoparticle delayed blast symptom expression on fingermillet leaves for 25days while it was on 15day in control plants. Chitosan naoparticle was able to induce the reactive oxygen species and the level of peroxidase actvitiy in leaves of fingermillet, which might be the reason for delayed symptom. The treated plants showed reduced disease incidence when compared to untreated control plants. These results suggested the role of chitosan nanoparticle in protecting fingermillet plants from P. grisea infection.

Tracing QTLs for Leaf Blast Resistance and Agronomic Performance of Finger Millet (Eleusine coracana (L.) Gaertn.) Genotypes through Association Mapping and in silico Comparative Genomics Analyses.

Finger millet is one of the small millets with high nutritive value. This crop is vulnerable to blast disease caused by Pyricularia grisea, which occurs annually during rainy and winter seasons. Leaf blast occurs at early crop stage and is highly damaging. Mapping of resistance genes and other quantitative trait loci (QTLs) for agronomic performance can be of great use for improving finger millet genotypes. Evaluation of one hundred and twenty-eight finger millet genotypes in natural field conditions revealed that leaf blast caused severe setback on agronomic performance for susceptible genotypes, most significant traits being plant height and root length. Plant height was reduced under disease severity while root length was increased. Among the genotypes, IE4795 showed superior response in terms of both disease resistance and better agronomic performance. A total of seven unambiguous QTLs were found to be associated with various agronomic traits including leaf blast resistance by association mapping analysis. The markers, UGEP101 and UGEP95, were strongly associated with blast resistance. UGEP98 was associated with tiller number and UGEP9 was associated with root length and seed yield. Cross species validation of markers revealed that 12 candidate genes were associated with 8 QTLs in the genomes of grass species such as rice, foxtail millet, maize, Brachypodium stacei, B. distachyon, Panicum hallii and switchgrass. Several candidate genes were found proximal to orthologous sequences of the identified QTLs such as 1,4-ß-glucanase for leaf blast resistance, cytokinin dehydrogenase (CKX) for tiller production, calmodulin (CaM) binding protein for seed yield and pectin methylesterase inhibitor (PMEI) for root growth and development. Most of these QTLs and their putatively associated candidate genes are reported for first time in finger millet. On validation, these novel QTLs may be utilized in future for marker assisted breeding for the development of fungal resistant and high yielding varieties of finger millet.

Perspectivas del uso de bacterias rizosféricas en el control de Pyricularia grisea (Cooke Sacc) en el cultivo del arroz (Oryza sativa L) / Prospect of the use of bacteria in the control Pyricularia grisea (Cooke Sacc) on rice (Oriza sativa L)

El arroz es fuente de alimento para una gran parte de la población mundial, con alto promedio de consumo anual. En este cultivo las enfermedades de origen microbiano constituyen uno de los factores que inciden en la obtención de bajos rendimientos y calidad de los granos. La piriculariosis o añublo del arroz, causada por Pyricularia grisea, es la enfermedad más importante en este cultivo en América Latina, ya que puede provocar hasta el 100% de reducción de los rendimientos. Como parte de la estrategia de agricultura sostenible, se trata de controlar estos patógenos y lograr altos rendimientos del cultivo mediante una combinación adecuada de fertilizantes químicos y productos biológicos. En este sentido, la aplicación de inoculantes bacterianos constituidos por bacterias promotoras del crecimiento vegetal (Plant Growth- Promoting Bacteria, PGPB, por sus siglas en inglés) ha constituido una alternativa ecológica que favorece la conservación del medioambiente y el ecosistema. Este trabajo tiene como objetivo abordar el estado actual y las perspectivas de uso de bacterias rizosféricas en el control de Pyricularia grisea en el cultivo del arroz, tratando algunos temas relevantes, como son las principales enfermedades que afectan al cultivo, los géneros de PGPB más utilizados para el control de las mismas y sus principales mecanismos de acción.

Rice is an important food supply for a large part of the world population and its consumption rates are very high. Microbial diseases are one of the main causes that provoke low yields and low-quality spotted grains. Although fungi, bacteria and viruses are mostly the responsible for these losses, fungal diseases strike more frequently. Among fungi, Pyricularia grisea, the blast fungus is responsible for up to 100% of reduction in yields, being the blast the most important rice disease in Latin America. To control this pathogen, a strategy of sustainable agriculture might be developed, combining accurately chemical and biological products. PGPB based bioproducts have been considered as an eco-friendly alternative, which favours environment preservation. This work was aimed to approach the current status and outlook of the use of rhizobacteria in the biocontrol of Pyricularia grisea on rice. Main diseases attacking rice, most beneficial PGPB and its mechanisms of action will be discussed too in this review.