Geographic Distribution of Avirulence Genes of the Rice Blast Fungus Magnaporthe oryzae in the Philippines

Abstract

A total of 131 contemporary and 33 reference isolates representing a number of multi-locus genotypes of Magnaporthe oryzae were subjected to a PCR test to detect the presence/absence of avirulence (Avr) genes. Results revealed that the more frequently occurring genes were Avr-Pik (81.50%), Avr-Pita (64.16%) and Avr-Pii (47.98%), whereas the less frequently occurring genes were Avr-Pizt (19.08%) and Avr-Pia (5.20%). It was also laid out that the presence of Avr genes in M. oryzae is strongly associated with agroecosystems where the complementary resistant (R) genes exist. No significant association, however, was noted on the functional Avr genes and the major geographic locations. Furthermore, it was identified that the upland varieties locally known as “Milagrosa” and “Waray” contained all the R genes complementary to the Avr genes tested.

Population-level whole genome sequencing ofAscochyta rabieiidentifies genomic loci associated with isolate aggressiveness

“…Therefore, although genetic variations detected in the repetitive regions of the genome were annotated as intergenic, these could potentially be located on effector loci, which have not been annotated due to their highly divergent sequences and low homology to known effectors. High levels of presence/absence polymorphisms of effectors have been reported within fungal plants pathogens such as Magnaporthe oryzae (97) and Blumeria graminis (81). Although the percentage of repetitive regions in A. rabiei is considerably lower than many other aggressive plant pathogens such as Leptosphaeria maculans (Fig.…”

Engineering effector‐triggered immunity in rice: Obstacles and perspectives

“…Liu, Zhu et al, 2021;Ning et al, 2020). The investigation of rice blast population and evolution has disclosed the effector distribution in different areas such as the Philippines (Lopez et al, 2019), Thailand (Sutthiphai et al, 2022), China (Hu et al, 2022) and Asia (Fukuta, 2020), which has facilitated the selection of R gene(s) to employ in each area.…”

“…In rice, several R genes, defence‐regulator genes and quantitative trait loci have been used to generate varieties with enhanced resistance against rice blast, sheath blight and bacterial blight (W. Li, Chern et al, 2019; Z. Liu, Zhu et al, 2021; Ning et al, 2020). The investigation of rice blast population and evolution has disclosed the effector distribution in different areas such as the Philippines (Lopez et al, 2019), Thailand (Sutthiphai et al, 2022), China (Hu et al, 2022) and Asia (Fukuta, 2020), which has facilitated the selection of R gene(s) to employ in each area. However, the drawbacks of this approach are that it is labour‐intensive and time‐consuming (W. Li et al, 2020); the appearance of unwanted traits by linkage drag; short life of the introduced R gene (W. Li et al, 2020); and reduced resistance caused by R gene interaction (Mundt, 2018).…”

Bioinformatic Detection of Positive Selection Pressure in Plant Pathogens: The Neutral Theory of Molecular Sequence Evolution in Action

“…Take for example known Avr genes in Magnaporthe oryzae. Out of 164 isolates collected from various regions in the Philippines, between 5 and 81% contained each of the known Avr genes Avr-Pik, Avr-Pita, Avr-Pii, Avr-Pizt, and Avr-Pia (Lopez et al, 2019). The fact that none of these genes occur in all isolates suggests that loss of effector genes is a common response in M. oryzae populations to recognition by R genes.…”