The Rice Xa3 Gene Confers Resistance to Xanthomonas oryzae pv. oryzae in the Model Rice Kitaake Genetic Background

Diversity of transcription activator-like effectors and pathogenicity in strains of Xanthomonas oryzae pv. oryzicola from Yunnan

The present study aimed to evaluate transcriptional activator-like effector (TALE) genes in 86 Xanthomonas oryzae pv. oryzicola strains collected from 8 rice-growing regions in Yunnan, and to examine the relationship between TALE genotypes and virulence in 6 differential rice lines. Besides, the geographical areas, distribution of these genotypes were studied in detail. Genetic diversity was analyzed through the number and size of putative TALE genes based on TALE gene avrXa3 as a probe. We found that X. oryzae pv. oryzicola strains consist of variable number (13-27) of avrXa3-hybridizing fragments (putative TALE genes). Test strains were classified into 8 genotypes (G1-G8) with major genotypes G3 and G7 widely distributed in Yunnan. Pathogenicity of X. oryzae pv. oryzicola was evaluated by inoculating 6 differential rice lines with a single resistance gene into 9 pathotypes clusters (I-IX), the dominant Genotypes G3 and G7 consist of pathotypes I, II, and IV. Furthermore, we also detected the known TALE target genes expression in susceptible rice cultivar (cv. nipponbare) after inoculating 8 genotypes-representative X. oryzae pv. oryzicola strain. Correlation between the numbers of putative TALE genes of X. oryzae pv. oryzicola and relevant target genes in nipponbare confirmed up-regulation. Altogether, this study has given insights into the population structure of X. oryzae pv. oryzicola that may inform strategies to control BLS in rice.

Novel and emerging biotechnological crop protection approaches

Traditional breeding or genetically modified organisms (GMOs) have for a long time been the sole approaches to effectively cope with biotic and abiotic stresses and implement the quality traits of crops. However, emerging diseases as well as unpredictable climate changes affecting agriculture over the entire globe force scientists to find alternative solutions required to quickly overcome seasonal crises. In this review, we first focus on cisgenesis and genome editing as challenging biotechnological approaches for breeding crops more tolerant to biotic and abiotic stresses. In addition, we take into consideration a toolbox of new techniques based on applications of RNA interference and epigenome modifications, which can be adopted for improving plant resilience. Recent advances in these biotechnological applications are mainly reported for non-model plants and woody crops in particular. Indeed, the characterization of RNAi machinery in plants is fundamental to transform available information into biologically or biotechnologically applicable knowledge. Finally, here we discuss how these innovative and environmentally friendly techniques combined with traditional breeding can sustain a modern agriculture and be of potential contribution to climate change mitigation.