Identification and Analysis of the Pathogenic Types of Hemileia vastatrix in the Coffee Germplasm Fields of the Main Coffee Planting Areas in China

Purpose To study the pathogenic types of coffee leaf rust (CLR) caused by the obligate parasitic pathogenic fungus Hemileia vastatrix in the coffee germplasm fields of the main coffee planting areas in China, guiding the layout of the varieties as well as to select the resistant varieties in the main planting areas.

Methods CLR disease samples were collected from four representative coffee germplasm fields distributed in the main coffee cropping areas of China, and carried out propagation and single spore isolation on super-sensitive genotypes. Virulence genes of H. vastatrix were clarified in specific genotypes and the corresponding pathogenic types were deduced.

Results 42 samples (73.68%) of the total 57 CLR samples were successfully expanded, of which 27 samples (64.29%) that were successfully saved and divided into 23 CIFC entries according to the sample information. There were three pathogenic types detected, of which XXXVII (v_2,5,6,7,9) (86.96%) was the dominant pathogenic type, followed by New race (v_2,5,6,7) (8.69%) and XXXIV (v_2,5,7,9) (4.35%). New race (v_2,5,6,7) had not been reported in CLR survey of other germplasm resource nurseries in China.

Conclusion The genetic structure of the H. vastatrix populations is changing. The original pathogenic types have infiltrated into the germplasm fields located in the main coffee cropping area and accelerated the evolution on the host with similar genotypes. The new pathogenic types randomly flow between the coffee bases and the germplasm fields across the main cropping area of coffee and pose a threat to the resistance of the current main cultivars. This study will provide an important basis for the scientific management of coffee germplasms and provide theoretical supports for the prevention and control of CLR.