Abstract
This work was carried out with the objective of performing a molecular and aggressiveness characterization of F. solani and F. oxysporum f.sp. passiflorae collected in the Pantanal, Cerrado and Amazon biomes. We selected the most aggressive isolates for use in breeding programs aiming resistance to Collar Rot and Fusariosis. For inoculation of the isolates of F. oxysporum f.sp. passiflorae the washed root method was used. The molecular characterization of the isolates was carried out by partial sequencing of the Transcribed Internal Spacer of the rDNA region. The isolates of F. solani formed two distinct groups in relation to aggressiveness. Among all isolates, FSUNEMAT 40 and FSUNEMAT 46 were the most aggressive. The model with K=2 was taken as the best model to explain the genetic structure of the F. solani populations, with clear combinations of genes from both gene pools. There were three groups with respect to the aggressiveness of the isolates of F. oxysporum f.sp. passiflorae, with the isolated FOUNEMAT 22 being the most aggressive. In view of these results, the isolates of F. solani collected in P. edulis in the state of Mato Grosso presented a high molecular variability independent from the biome of origin, and this was also observed in the tests of aggressiveness. The results indicate the need to consider the molecular variability and the aggressiveness of the pathogens in the evaluation of genotypes of sour passion fruit in programs of selection of resistant cultivars.
Highlights
The cultivation of passion fruit, Passiflora edulis, has been growing every year in Brazil, occupying a prominent position in tropical fruit growing (MAPA, 2016)
One of the main problems that contributes to the reduction in productivity of the passion fruit crop is the occurrence of diseases, such as collar rot and fusariosis, caused respectively by the fungi Fusarium solani Martius and Fusarium oxysporum f.sp. passiflorae (Fischer & Rezende, 2008)
By analyzing the data contained in the analysis of variance, it was possible to observe a significant difference between the means of the isolates at 1% probability by F test for almost all characteristics analyzed, except for LL, which was significant at 5%
Summary
The cultivation of passion fruit, Passiflora edulis, has been growing every year in Brazil, occupying a prominent position in tropical fruit growing (MAPA, 2016). The state of Mato Grosso is the largest producer in the Midwest region, totaling 5,275 tons in a cultivated area of 346 hectares This production is still very low when compared to the state of Bahia, which produces an average of 342 thousand tons/year (IBGE, 2016). Passiflorae (Fischer & Rezende, 2008) Plants infected by these fungi initially present wilting of the nodes and, with the progress of the disease, there is early defoliation, wilting and death of the plant in a few days. These symptoms are the result of the damage caused by these fungi to the vascular system of plants (Fischer & Rezende, 2016). The presence of F. solani and F. oxysporum f.sp. passiflorae in the soil may even prevent the cultivation of passion fruit for years since these pathogens have a resistance structure (chlamydospore) that guarantees fungus survival (Bueno et al, 2006)
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