Strawberry germplasm response to Fusarium oxysporum f. sp. fragariae under greenhouse conditions, and identification of sources for resistance in Mexico

Strawberry dry wilt caused by Fusarium oxysporum f. sp. fragariae (Fof) is one of the major diseases in the Central Region of Mexico. Currently planted cultivars are susceptible to this disease. Chemical soil disinfection is expensive and polluting, therefore, it is important to develop resistant cultivars. INIFAP has generated advanced clones with field tolerance to Fof, but their reaction is unknown to artificial inoculation with the fungus. The objective of this study was to determine, under greenhouse conditions, the genetic advance for tolerance to Fof in 29 strawberry clones developed at INIFAP, and to evaluate 13 foreign cultivars, as possible resistance sources. All plants were inoculated artificially with high and low inoculum doses of Fof. To estimate the resistance level, the Area Under the Disease Progress Curve (AUDPC), and the severity of Fof in roots and crowns were evaluated. The highest AUDPC at both inoculum doses was shown by clones 08.3, 10.40, 08.443 and 'Camino Real' and 'Ventana'. These genotypes showed the highest severity in roots and crowns, being the most susceptible. Furthermore, clones 08.268, 141.1E3, 01.7, 10.18 and 'Fairfax', showed the lowest AUDPC; however, 'Fairfax', clones 141.1E3, 99.777, 07.35 and ' Klondike' exhibited the least severity of roots and crowns, the last three genotypes shown an intermediate AUDPC. Therefore, the germplasm that can be used as progenitors to introduce resistance to Fof are 'Fairfax' and clone 141.1E3, as the most resistant and clones 08.268, 01.7, 10.18, 99.777, 07.35 and 'Klondike' as moderately resistant. These results confirm that the field selection for Fof tolerance was efficient, because six of the resistant progenitors were derived from the INIFAP's strawberry breeding program. Field selection was carried out by their productivity and agronomic attributes, includes clones 08.268, 01.7 and 07.35 as outstanding. Among the foreigner cultivars, only 'Fairfax' and 'Klondike' were resistant to Fof.