BackgroundIn February 2016, a new fungal disease was spotted in wheat fields across eight districts in Bangladesh. The epidemic spread to an estimated 15,000 hectares, about 16 % of the cultivated wheat area in Bangladesh, with yield losses reaching up to 100 %. Within weeks of the onset of the epidemic, we performed transcriptome sequencing of symptomatic leaf samples collected directly from Bangladeshi fields.ResultsReinoculation of seedlings with strains isolated from infected wheat grains showed wheat blast symptoms on leaves of wheat but not rice. Our phylogenomic and population genomic analyses revealed that the wheat blast outbreak in Bangladesh was most likely caused by a wheat-infecting South American lineage of the blast fungus Magnaporthe oryzae.ConclusionOur findings suggest that genomic surveillance can be rapidly applied to monitor plant disease outbreaks and provide valuable information regarding the identity and origin of the infectious agent.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-016-0309-7) contains supplementary material, which is available to authorized users.

Background: In February 2016, a new fungal disease was spotted in wheat fields across eight districts in Bangladesh. The epidemic spread to an estimated 15,000 hectares, about 16 % of the cultivated wheat area in Bangladesh, with yield losses reaching up to 100 %. Within weeks of the onset of the epidemic, we performed transcriptome sequencing of symptomatic leaf samples collected directly from Bangladeshi fields. Results: Reinoculation of seedlings with strains isolated from infected wheat grains showed wheat blast symptoms on leaves of wheat but not rice. Our phylogenomic and population genomic analyses revealed that the wheat blast outbreak in Bangladesh was most likely caused by a wheat-infecting South American lineage of the blast fungus Magnaporthe oryzae.

Strawberry is a well-known source of natural antioxidants with excellent free radical scavenging capacity. This study determined the effects of chitosan application in field condition on plant growth, fruit yield and antioxidant activities in strawberry fruit. Foliar applications of chitosan on strawberry significantly increased plant growth and fruit yield (up to 42% higher) compared to untreated control. Increased fruit yield was attributed to higher plant growth, individual fruit weight and total fruit weight/plant due to the chitosan application. Surprisingly, the fruit from plants sprayed with chitosan also had significantly higher contents (up to 2.6-fold) of carotenoids, anthocyanins, flavonoids and phenolics compared to untreated control. Total antioxidant activities in fruit of chitosan treated plants were also significantly higher (ca. 2-fold) (p< 0.05) than untreated control. To the best of our knowledge, this is the first report of chitosan applied on field plants providing significant improvement of both yield and health benefiting biochemical contents in strawberry fruit. Further study on the elucidation of mechanisms involved with enhancement of growth, yield and biochemical contents by chitosan is needed to promote sustainable production of strawberry.

Wheat blast is a devastating fungal disease caused by a filamentous fungus, Magnaporthe oryzae Triticum (MoT) pathotype, which poses a serious threat to food security of South America and South Asia. In the course of screening novel bioactive secondary metabolites, we found that some secondary metabolites from a marine Bacillus subtilis strain 109GGC020 remarkably inhibited the growth of M. oryzae Triticum in vitro at 20 µg/disk. We tested a number of natural compounds derived from microorganisms and plants and found that five recently discovered linear noncytotoxic lipopeptides, gageopeptides A-D (1-4) and gageotetrin B (5) from the strain 109GGC020 inhibited the growth of MoT mycelia in a dose-dependent manner. Among the five compounds studied, gageotetrin B (5) displayed the highest mycelial growth inhibition of MoT followed by gageopeptide C (3), gageopeptide D (4), gageopeptide A (1), and gageopeptide B (2) with minimum inhibitory concentrations (MICs) of 1.5, 2.5, 2.5, 10.0, and 10.0 µg/disk, respectively. Application of these natural compounds has also completely blocked formation of conidia in the MoT fungal mycelia in the agar medium. Further bioassay revealed that these compounds (1-5) inhibited the germination of MoT conidia and, if germinated, induced deformation of germ tube and/or abnormal appressoria. Interestingly, application of these linear lipopeptides (1-5) significantly suppressed wheat blast disease on detached wheat leaves. This is the first report of the inhibition of mycelial growth, conidiogenesis, conidial germination, and morphological alterations in the germinated conidia and suppression of wheat blast disease by linear lipopeptides from the strain of B. subtilis. A further study is needed to evaluate the mode of action of these natural compounds for considering them as biopesticides for managing this notorious cereal killer.

Wheat blast, caused by the Magnaporthe oryzae Triticum (MoT) lineage (synonym Pyricularia oryzae Triticum lineage), is a destructive disease in South America and Bangladesh. It is primarily a disease of wheat head, which can cause yield loss up to 100% under favorable disease conditions. The head infection results in complete or partial bleaching of the spike above the point of infection with either no grain or shriveled grain with low test weight. Due to low fungicide efficacy against the disease and lack of availability of resistant varieties, an integrated management program should be adopted to control this serious wheat disease. First of all, a convenient and specific diagnostic tool is needed for evaluating seed health and early detection in wheat field to initiate timely mitigation measures and thereby decreasing pathogen initial inoculum and dispersal. Second, we should have a better understanding of the epidemiology of the disease and develop a real-time disease monitoring and surveillance system to alert growers to apply management practices at an optimum time. Third, we need a better understanding of the infection biology of the fungus and its interaction with wheat plants at the tissue and molecular levels helpful for improving disease management. Fourth, breeding for resistance to wheat blast can be accelerated by using resistance genes such as 2NS translocation, Rmg8 and RmgGR119 or advanced genomic technology such as CRISPR-Cas. Fifth, integration of alternative disease management practices, such as biological control using antagonistic microorganisms or derivatives thereof to achieve sustainable approach for the management of wheat blast. Finally, a globally concerted effort is needed using open science and open data sharing approaches to prevent this seed-and airborne plant disease's widespread devastation of wheat crop. This comprehensive review updates our knowledge on wheat blast disease and discusses the approaches for its sustainable management for ensuring food and nutritional security of the ever-increasing global population.