The epidemiology of Verticillium dahliae and its effect on yield was studied for 3 years in three plots of olive cv. Picual, planted in soil previously cropped with highly susceptible V. dahliae host plants and irrigated with saline water. Disease incidence increased 2·2-, 2·6-and 1·5-fold in plots 3A, 9A and 9C, respectively, within 39, 25 and 15 months of the first record taken. The highest severities were recorded in spring 2001 (4·0, 5·3 and 5·4 on a scale of 2-10, respectively). Disease incidence and severity increased during winter-spring and decreased during summer. Seasonal changes were also observed in the isolation of V. dahliae ; the highest isolation rates in diseased trees were in winter (34%) and spring (45%), and the lowest were in autumn and summer (19-20%). Verticillium dahliae was isolated on an average of 27, 28 and 19% from the bottom, middle and top of the tree canopy, respectively, and was isolated from trees with and without symptoms. The fruit yield from diseased trees was reduced by an average of 75% in comparison with symptomless trees in plot 3A each year. A similar yield reduction (89%) was recorded in plot 9A in 2000. The severe expression of the disease and its effect on yield in the present study could be due to the fact that the orchard was planted in infested soil, and that saline irrigation probably exacerbates the problem.
Mango (Mangifera indica) is regarded as the king of fruits in India, where it has been cultivated for at least 4,000 years and has great cultural and religious significance. Many Indian mango cultivars originated in the fifteenth century when the best selections of mango seedlings were propagated by grafting and planted in large orchards, in some cases numbering 100,000 trees. With the arrival of voyagers to India from Europe, mango was soon established throughout the tropics and subtropics. Mango malformation disease (MMD) is one of the most important and destructive diseases of this crop. It affects inflorescences and vegetative portions of the plant. Although trees are not killed, the vegetative phase of the disease impedes canopy development and the floral phase reduces fruit yield dramatically; substantial economic losses can occur since malformed inflorescences do not bear fruit. Significant advances have been made in understanding the etiology of MMD, which is caused by more than one agent. However, until recently little progress had been made on the epidemiology of this disease. The results that are discussed in this article are only for MMD caused by F. mangiferae.
The influence of girdling on flower type and number, inflorescence density, and fruit set in 3 different olive cultivars (Barnea, Picual, and Souri) under intensive growing conditions using saline irrigation water was studied for 3 years. The density of inflorescences on the branches was not affected by girdling in any of the 3 cultivars during any of the 3 consecutive years studied. Also, no clear relation between the number of flowers and girdling was found in any of the 3 cultivars tested. The percentage of perfect flowers on the girdled scaffolds of cvv. Barnea and Picual increased significantly, except for Picual in 2002 where no differences were observed. However, no such difference between the non-girdled and girdled scaffolds was observed in cv. Souri. Comparison of fruit set on non-girdled and girdled scaffolds showed a similar and generally positive response to the treatment in the examined cultivars. However, in the third year of the study, no significant difference between the non-girdled and girdled scaffolds was observed. A significantly higher yield of the girdled trees was measured in the 3 cultivars during the first year after the winter girdling. Due to the young age of the trees the effect of girdling on yield was not further recorded. Fruit size on the girdled scaffolds was smaller than those from the non-girdled ones, as a consequence a higher percentage of fruit set was observed on the first ones. The results presented in this study point to different varietal responses of olive trees to girdling. However, this might also be due to the young age of the trees in this study as well as the peculiar agronomic condition of the trees.
The lichen Ramalina ecklonii (Spreng.) Mey. and Flot. was transplanted to 24 biomonitoring sites along three transects in the western area of Córdoba, Argentina, and tested for chlorophyll, phaeophytin conjugated dienes concentration, soluble protein content, and sulfur accumulation. The transects represented three levels of vehicular traffic. Significant differerences were observed in sulfur content, phaeophytin b, total phaeophytin, and dry mass to fresh mass ratio (DM/FM). A pollution index (PI) was calculated based on the ratio of phaeophytin a to chlorophyll a and the ratio of sulfur and conjugated dienes in transplanted specimens to sulfur and conjugated dienes in the control specimens. Significant differences in PI among the transects were observed; the lowest PI was at the control site, and the highest along the sampling line having the greatest amount of traffic. Key words: lichen, Ramalina ecklonii, biomonitoring, air pollution.
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