Effect of potassium silicate on epidemic components of powdery mildew on melon

The effects of silicon (Si) supplied in the form of potassium silicate (PS) were evaluated on epidemic components of powdery mildew of melon under greenhouse conditions. The PS was applied to the roots or to leaves. In the first experiment, epidemic components were evaluated after inoculation with Podosphaera xanthii. In the second experiment, the disease progress rate was evaluated on plants subjected to natural infection. The area under the disease progress curve was reduced by 65% and 73% in the foliar and root treatments, respectively, compared to control plants, as a consequence of reductions in infection efficiency, colony expansion rate, colony area, conidial production and disease progress rate. However, root application of PS was more effective than foliar application in reducing most of the epidemic components, except for infection efficiency. This can be explained by the high Si concentration in leaf tissues with root application, in contrast to the foliar treatment where Si was only deposited on the external leaf surfaces. The effects of PS reported in this study demonstrated that powdery mildew of melon can be controlled, and that the best results can be achieved when PS is supplied to the roots.

REDUCTION AND TIMING OF FUNGICIDE APPLICATION IN THE MANAGEMENT OF SCAB IN PLUM TREES

This work aimed to evaluate the incidence and severity of scab in prune trees under different fungicide management, with two time patterns of application; one at the early fruit formation, up to pit hardening, and another starting after pit hardening, and compare the number of fungicide application reductions with the management adopted by the producer Four experiments, with different treatments, were carried out during the 2004-2005 and 2005-2006 seasons (two experiments,) and that of 2008-2009, using the Harry Pickstone and Reubennel cultivars. The most efficient control of the disease was achieved with the combination of metiram, piraclostrobina e ditianona fungicides from late bloom to pit hardening. Efficient scab control in prune was dependent on the combination of the fungicides used and the application timing. Reduced fungicide management is possible, while spraying initiated after pit hardening was not efficient for scab control.

Inheritance of resistance to powdery mildew in pea and pathogenesis-related aspects

The inheritance of resistance to powdery mildew in the pea cultivar MK-10 and some histological aspects of infection were assessed. For the inheritance study, F1, F2, backcrosses and F3 generations of MK-10 crossed with two susceptible populations were evaluated. Histological evaluations included percentage of germinated conidia, percentage of conidia that formed appresoria, percentage of conidia that established colonies, and number of haustoria per colony. Segregation ratios obtained in the resistance inheritance study were compared by Chi-square (ײ) test and the histological data were analyzed by Tukey's test at 5% probability. It was concluded that resistance of MK-10 to powdery mildew is due to a pair of recessive alleles since it is expressed in the pre-penetration stage and completed by post-penetration localized cellular death, characteristic of the presence of the pair of recessive alleles er1er1.