A new report in Science has found that farmers in Brazil in the 1980s are responsible for the for the spread of Rice Blast Fungus to wheat plants. Scientists were able to back track the evolution of the fungus to a strain of wheat called Anahuac which lacked the capability to recognize the fungal invader. In spreading to the Anahuac wheat strain the fungus gained a foothold by which it could then spread to other strains of wheat which has caused a significant amount of crop loss the world over. By finding the origins of the fungal host jump it becomes more likely that the spread of the disease may be contained better before it manages to become a major threat to the global wheat population. Furthermore in identifying the process a similar turn of events may be prevented in other plant species namely in the the avoidance of introducing crop species which lack defensive genes into regions known to possess parasites capable of making cross species jumps.
The original research was primarily conducted by Yoshihiro Inoue and Trinh T. P. Vy of the University of Kobe and was accepted into Science. The researches utilized two previously identified genes common to between oats, ryegrass, and wheat which were capable of suppressing the fungal infection PWT3 and PWT4 as well as the corresponding resistance genes found in the fungus. Testing occurred on spikes of four different wheat cultivars which were each introduced to isolates of the fungus taken from wheat plants as well as vectors for the PWT3 and PWT4 genes. The fungus was able to infect all the wheat strains and was suppressed by the transformed wheat plants. By backtracking the progression of the genome of the fungus based off of historical isolate samples the PWT3 homologues were found to have emerged in a functional form prior to the PWT4 ones became functional and the earliest isolate to possess the gene was found to be from Brazil in the the nineteen nineties and a majority of modern isolates shared the particular genotype originating in Brazil. Furthermore in surveying the cultivars used as wheat crops the researchers found the singular cultivar that lacked both the PWT3 and PWT4 genes that was in use in the region at the time the Anahuac cultivar which in turn allowed for the fungus to colonize its first vulnerable wheat plant.