Title : Durability of the Genetic Resistance to the Coffee Rust (Hemileia vastatrix) in Improved Varieties in Hounduras 2019
Abstract:
Coffee rust (Hemileia vastatrix) is the main fungal disease of the crop worldwide, causing losses of 25 to 30% of production during protracted epidemics. To address this disease, several research efforts have been made aimed at understanding the pathogen, its interaction with the plant and climate and identifying resistance genes for the development of improved varieties, writing to date 9 resistance genes (SH1 to SH9) and 9 virulence genes (v1 to v9) using the differentiating plants initiated by Mayne in 1932 and continued by the International Coffee Rust Research Center (CIFC) in Portugal where they started crossbreeding between the Timor Hybrid 832/1 and 832 / 2 with Caturra and Villa Sarchi that derived in early generations from Catimores and Sarchimores sent to Honduras by PROMECAFE, for evaluation and release after a rigorous selection process producing varieties such as IHCAFE 90 in 1990, Lempira (1998) and Parainema in 2004, which have replaced susceptible varieties such as Pacas, Typical, Borbon and Catuai, dominating 65% of the cultivated area by 2012 where about 45% is Lempira variety that contributed to increased national productivity but created high vulnerability to emerging epidemics due to mutation effects, dispersion and genetic recombination of the fungus, favored by the low genetic diversity of resistance in the field. To minimize the risk, the genetic improvement program of the IHCAFE monitors plots of mother plants, seed foundation, research trials and farms of producers, registering the presence or absence of coffee rust, this allowed from 2007 to date to identify early and progressive the loss of resistance in the Lempira variety released in 1998 due to a low sporulation coffee rust in La Fé Peña Blanca Cortes and in 2015 the complete susceptibility of the F1 Millennium, Icatu 48 and Icatu 75. In 2017, identifying Lempira as susceptible after 17 years to be released before new coffee rust population with 5 new virulence genes (V1,4,6,7 and 9) identified by differentiating plants inoculated with coffee rust mass samples that in turn affect 20% of the IHCAFE 90 variety released in 1990, said study identified that only H27, Parainema, Centroamericano, Anacafe 14 and Batian are immune to the new coffee rust in 2017. With the exception of the H27 Susceptible in 2018 and the Centroamemricano in 2019. For the previously documented in Honduras the durability of the coffee rust resistance can vary between 8 and 25 years but the exact time can not be predicted, therefore it is necessary to increase the durability incorporating more major genes of resistance such as the SH3 gene present in Coffea liberica, consider the crossing of genera, induction of mutations and implement test crosses and study of progenies F2 as a prerequisite to the release of new resistant varieties of greater complexity of genetic resistance developed to limit the opportunities to fix pathogen mutations and the frequency of epidemic events in the coffee producing country or region.
