La resistencia de las variedades mejoradas contra la roya diariamente se pone a prueba, y la única manera de conservar la durabilidad de la resistencia es incorporando nuevos genes o combinación de mecanismos de resistencia contra esta enfermedad. Por ello, actualmente Cenicafé, trabaja de manera anticipatoria desarrollando líneas avanzadas que posean fuentes de resistencia diferentes a las que poseen las variedades comerciales actuales provenientes del Híbrido de Timor, los cuales serán incorporados a las futuras variedades de café.

En los programas de mejoramiento genético vegetal, los objetivos son diversos, entre ellos se encuentra eldesarrollar genotipos altamente productivos, de amplia adaptabilidad y con resistencia genética a patógenos limitantes para el cultivo. Para el caso de resistencia a enfermedades, es relativamente fácil de lograr cuando se cuenta con fuentes de genes y la expresión de estos es monogénica – dominante. En este caso, pueden obtenerse variedades con resistencia genética de tipo vertical; sin embargo, este tipo de resistencia rápidamente puede ser vencida por patotipos compatibles, y cuando esto sucede, debe recurrirse a un cambio en la estrategia, con el fin de lograr que la resistencia de plantas a patógenos perdure en el tiempo y su durabilidad se logra mediante el uso de la resistencia genética horizontal o cuantitativa. Este tipo de resistencia sólo estará presente en variedades poseedoras de diversidad genética, factor condicionante que las hace más aptas para enfrentar a futuro factores de riesgo. En esta revisión se hace una recopilación de conceptos generales, factores que afectan la resistencia y avances logrados en la comprensión de la resistencia genética de tipo horizontal de Coffea arabica L. y Coffea canephora Pierre ex Froehner.

El Centro Nacional de Investigaciones de Café-Cenicafé optó por la estrategia de utilizar la diversidad genética como eje central para la obtención de variedades de café con resistencia durable a la roya del cafeto. Dentro de este concepto, las variedades desarrolladas por Cenicafé son compuestas, lo que significa que son la mezcla de diferentes progenies que difieren en su nivel de resistencia pero que comparten excelentes atributos agronómicos como producción, calidad física del grano y calidad sensorial.

Coffee berry disease (CBD) is not present in the Americas and presents a potential risk for growing coffee. Therefore, Colombia, which has been in scientific cooperation with the Centro de Investigação de Ferrugens do Cafeeiro (CIFC) of Portugal for more than 30 years, has been evaluating the genetic resistance of nine populations of C. arabica to 13 isolates of Colletotrichum kahawae JM Waller and PD Bridge, which are diverse in terms of aggressiveness and geographical origin. The phenotypes observed in the interaction between C. arabica and C. kahawae were used to develop a statistically reliable scale (p-value ≥ 0.001) to categorize resistance in C. arabica into five classes, and this scale was used to classify the nine populations of C. arabica evaluated. The results allowed us to corroborate the potential of Timor Hybrid CIFC 1343 (TH CIFC 1343) as a source of genetic resistance to CBD and to identify new genetic sources not yet explored for the development of varieties in Colombia that may eventually mitigate the effects of CBD in the face of increasing rainfall events and minimum temperatures due to climate change, which can favor disease development. Additionally, the results suggest that the existence of races in the C. arabica–C. kahawae complex is probable, and a selection of genotypes was identified as a possible differential series of races in C. kahawae.

Three hybrid populations (F1) of Coffea arabica were evaluated under field and laboratory conditions, derived from sources carrying the SH1 coffee leaf rust (CLR) resistance gene and the CX.2385 line, obtained from the Caturra × Timor Hybrid CIFC-1343. The results obtained under controlled conditions and analyzed using survival curves allowed to estimate the probable times (p < 0.05) for the development of symptoms associated with CLR in the plants of populations evaluated. Phenotypic variation was observed as a defense response to Hemileia vastatrix infection, and plants with incomplete resistance to CLR were identified via an evaluation using the increasing lesions scale. The plants with incomplete resistance exhibited a delay in the development of the incubation period and an absence of the development of the dormancy period. Data suggest that when resistance genes in the sources are defeated by compatible strains, their recombination can give rise to new levels of resistance in the progeny. Additionally, the detached leaf methodology is recommended as an alternative to preselect genotypes with resistance to CLR, thus reducing the number of plants that are finally planted for field evaluations.

Coffee berry disease (CBD) is caused by the fungus Colletotrichum kahawae Waller and Bridge. This disease is restricted to the African continent, where it can cause production losses of more than 80% when susceptible varieties are used or when the indicated chemical control is not carried out. For this reason, since 1970, Cenicafé has developed lines resistant to this disease in the absence of the pathogen, a process that has been favored by the discovery and validation of microsatellite markers associated with the Ck-1 gene for resistance to CBD. In this research, 12 populations of Coffea arabica were characterized for their resistance to CBD using the molecular markers Sat235, Sat207 and FR34-6CTG. The molecular markers allowed us to identify that the same allelic form of resistance to CBD is present in lines derived from Timor Hybrid CIFC 1343 (HdT CIFC 1343). Furthermore, the allelic form of resistance associated with the three molecular markers was identified in one line derived from Coffea canephora. In lines derived from Caturra x HdT CIFC 1343 it was evident that, when the plants present the allelic forms of resistance identified by the molecular markers, high percentages of hypocotyls resistant to different isolates of C. kahawae are observed in the progeny. Key words: CBD; Coffea spp; resistance genes; marker-assisted selection.