RESUMEN
Hass avocado fruit diseases are one of the main marketing constraints in Colombia. To identify and reveal the diversity of fungi associated with diseases in fruits and peduncles, symptomatic samples were collected from 67 farms in the 9 main Hass avocado-producing municipalities of the department of Cauca located in southwestern Colombia. A total of 237 monosporic isolates were obtained that were subjected to DNA extraction, amplification of the ITS region, sequencing and functional diversity analysis based on Hill numbers by municipality and altitude. The results indicated that the genera Pseudocercospora, Diaporthe, Colletotrichum, Neofusiococcum, Lasiodiplodia and Pestatoliopsis were associated with fruit diseases. The genus with the highest number of effective species was Colletotrichum. The ITS region revealed 100% identity of the species Pseudocercospora norchiensis, which was the first report of this pathogen in the crop. There was a greater richness and diversity of associated species in the three municipalities, revealing that the higher the altitude was, the lower the richness and diversity of fungi associated with fruit diseases. These results will provide a better understanding of the identification and diversity of pathogenic microorganisms present in avocado production systems in this region of Colombia.
RESUMEN
RESUMEN El maracuyá es una especie susceptible a patógenos, como Fusarium solani f. sp. passiflorae, causante de la secadera, llegando a causar pérdidas entre 90 y 100%, en cultivos comerciales en Colombia. Debido al desconocimiento de un método de inoculación eficiente para evaluar germoplasma de maracuyá contra este patógeno, se planteó este estudio, cuyo objetivo fue comparar cuatro métodos de inoculación de F. solani f. sp. passiflorae MViRi01 en plántulas de maracuyá (Passiflora edulis f. flavicarpa), cultivadas a 29°C, con un fotoperiodo de 12h. Los tratamientos fueron: incisión en el tallo (T1), inmersión de raíces (T2), inyección en el tallo (T3) y cribado en tubos de ensayo modificado (T4). Se estimó la incidencia de la enfermedad y el periodo de incubación del hongo. Los métodos evaluados mostraron diferencias altamente significativas (P<0,001). F. solani f. sp. passiflorae infectó raíces, tallo y hojas, causando estrangulamiento ascendente y descendente del tallo. Se obtuvo 100% de incidencia de la enfermedad con los tratamientos T1 (incisión) y T4 (cribado). En T4, el periodo de incubación del hongo fue 2,4 días y en T2 (inmersión), de 19 días. La muerte de las plántulas ocurrió 12 días después de inocular los tratamientos T1 y T3 (inyección). La emisión de raíces adventicias en las plántulas se indujo inyectando el patógeno (T3). Los métodos apropiados para inocular Fusarium sp. en plántulas de maracuyá fueron el cribado en tubos de ensayo modificado y la incisión en el tallo, debido a la homogeneidad en los resultados y la replicabilidad.
SUMMARY Passionfruit is a species susceptible pathogens such as Fusarium solani f. sp. passiflorae, causal agent of Passiflora collar rot, which can cause yield losses between 90 and 100% in commercial crops in Colombia. Due to lack of knowledge of an efficient inoculation method to evaluate germplasm of passionfruit against this fungus, it was designed this study, whose objective was to compare four methods of inoculation of F. solani f. sp. passiflorae MViRi01 in passionfruit seedlings (Passiflora edulis f. flavicarpa) cultivated at 29ºC and 12-hours of photoperiod. The treatments were: stem incision (T1), root immersion (T2), stem injection (T3), and a modified test-tube screening methodology (T4). Disease incidence and incubation period of the fungus was evaluated. The assessed methods showed highly significant differences (P< 0.001). F. solani f. sp. passiflorae infected roots, stem, and leaves causing stem ascending and descending strangulation. Both T1 (incision) and T4 (screening) treatments showed 100% of disease incidence. The incubation period of the fungus in T4 was 2.4 days and in T2 (immersion) 19 days. The death of the seedlings occurred 12 days after inoculation in T1 and T3 (injection) treatments. The adventitious root sprouting in the seedlings was induced by injecting (T3) the pathogen. The most suitable methods to inoculate F. solani f. sp. passiflorae on passionfruit seedlings were the modified testtube screening methodology and the stem incision due to its homogeneity and replicability results.
