Coffea arabica Variety Trials Reveal Genotype by Environment Interactions In Resistance To Coffee Leaf Rust (Hemileia vastatrix)

Jorge Carlos Berny Mier y Teran^1*Solène Pruvot-Woehl^1,2Catherine Maina¹Santos Barrera¹James Mwita Gimase³Brahim Banda⁴Albertino Meza⁵Nathan Aliel Kachiguma⁶Elijah K Gichuru³Julio Alvarado^1,7Suresh Kumar⁸Jonny Alonso Castillo⁹Beatriz Moreno Lopez¹⁰Ariana Karina Román Ruíz¹¹Ari Wibowo¹²Never Mwatsiya¹³Jeena Devasia⁸Divya Kallingapuram Das⁸Edgardo Alpizar¹⁴Melanie Bordeaux⁹Rizqi Rizqi Akbar¹²Piet Van Asten¹⁵Jean Baptiste Kayigamba¹Paul Mulemangabo¹⁶Godfrey Sseremba¹⁷Hans Alexander Mendez Mendoza¹⁸Benit Mate¹⁶Mvuyekure Simon Martin¹⁹Jane Jerono Cheserek³Rosalío López Morgado²⁰Chemutai Job Alunga¹⁷Nayani Suryprakash Rao⁸Samson Rusenga¹³Tania Humphrey¹Christophe Montagnon²¹

• ¹World Coffee Research, Oregon, United States
• ²TechnoServe, Kigali, Rwanda
• ³Kenya Agricultural and Livestock Research Organization, Nairobi, Kenya
• ⁴OLAM, Kateshi, Zambia
• ⁵Cooperativa CENFROCAFE, Cajamarca, Peru
• ⁶Department of Agricultural Research Services, Mzuzu, Malawi
• ⁷AGROLAV, Santa Ana, El Salvador
• ⁸Central Coffee Research Institute, Chikkamagaluru, Karnataka, India
• ⁹NicaFrance Foundation, Finca La Cumplida, Matagalpa, Nicaragua
• ¹⁰Asociación Nacional del Café, Ciudad de Guatemala, Guatemala
• ¹¹El Colegio de la Frontera Sur, Chiapas, Mexico
• ¹²Indonesian Coffee and Cocoa Research Institute, Jember, Indonesia
• ¹³Coffee Research Institute, Chipinge, Zimbabwe
• ¹⁴ECOM, Managua, Nicaragua
• ¹⁵olam, Paksong, Laos
• ¹⁶National Institute for Agronomic Study of the Belgian Congo, Mulingu, Democratic Republic of Congo
• ¹⁷National Coffee Research Institute, Kampala, Uganda
• ¹⁸Café Finca Mountain Villa Rica, Chanchamayo, Peru
• ¹⁹Rwanda Agriculture Board, Kigali, Rwanda
• ²⁰Instituto Nacional de Investigaciones Forestales, Agricolas y Pecuarias, Veracruz, Mexico
• ²¹RD2 Vision, Valflaunes, France

Coffee Leaf Rust (CLR), caused by the obligate parasitic fungus Hemileia vastatrix, is the most consequential constraint in Arabica coffee production worldwide. The disease is ubiquitous, and in severe infections, it can defoliate coffee plants impacting yield and quality. The use of resistant varieties is the most cost-effective and sustainable strategy for coffee leaf rust management. Identification of highly resistant varieties as well as identifying environments in which these varieties perform similarly is a necessary step in breeding programs. An international multi-institutional effort involved the evaluation of 29 varieties, developed by different breeding programs in coffee-producing countries across the globe, for CLR severity in field conditions in 23 sites in Africa, Asia, and Latin America. The results showed that both the genotype and genotype by site interaction were highly significant, indicating that the resistance to coffee leaf rust not only depends on the genetic makeup but also can rank differently between sites. In general, varieties with interspecific introgressions were more resistant than the non-introgressed pure Arabicas. Although stability and overall resistance were correlated, some of the most resistant varieties were not the most stable. Four mega-environments were identified, and sites that are better at discriminating for resistance were identified in the three continents. Overall, this multi-institutional cooperation led to the identification of locally and globally highly resistant Coffee Leaf Rust varieties as well as understanding of their underlying genetics and further causes of genotype by environment interactions regarding coffee leaf rust resistance.