Full text
| |
| Author(s): |
Leila de Castro Louback Ferraz
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2001-06-04 |
| Advisor: | Armando Bergamin Filho |
| Abstract | |
The effect of different temperatures and crop mulch in the inactivation of the sclerotia of Sclerotinia sclerotiorum was studied. ln three field experiments, the covering with com crop mulch and the solarization of the soil in relation to the viability of sclerotia was studied for three months. Sclerotia were produced in carrot+cormmeal medium at 20℃ and incorporated into the soil (oven experiment), or conditioned in involucres and buried in the soil at 5, 10 and 30 cm (field experiment). The soil treatments in the field were: solarization (S), non-solarization (NS), and crop mulch added to solarized soil (PS). Sclerotia samples were collected every 30 days to observe the viability and presence of contaminants in NEON medium. The oven-heating of the soil at 50 and 60℃ and the use of diverse types of crop mulch inactivated the sclerotia, which had a higher incidence of contaminants. ln the field, the effect of soil solarization was significant. The sclerotia were killed in S after 90 days in the first experiment at three depths and in PS after 60 days at 5 and 10cm in the other two experiments. The incidence of contaminant in sclerotia in solarized soils was significant with a higher rate in S, followed by PS; however, a larger variability of contaminants was observed in PS. Temperatures of the soil in PS were higher when compared to the other treatments at the same depth. The effect of different mulch coverings on the soil in the formation of apothecia was studied in two experiments under controlled conditions. ln the first experiment, com, wheat, bean, quinoa, amaranthus, niger and millet straw were used; and in the second, com, wheat, bean, neem, amaranthus, sorghum and millet. Treatments with uncovered soil always produced a large number of apothecia. Sclerotia were produced in carrot+commeal medium for 30 days, in darkness at 20℃, and later used in the infestation of the soil contained in pots, then covered with straw. The pots were kept humid at 18℃ (10h light/ 14h darkness). The number of apothecia, the C/N relationship and the height ofthe straw were observed. The presence of amaranthus and quinoa straw in the first experiment, and amaranthus and neem, in the second, reduced apothecia production, unlike the niger straw in the first experiment, and bean in the second. Treatments with uncovered soil always produced a large number of apothecia. A similar procedure was done in the field in experimental portions with the cultivation of beans. A controlled portion with uncovered soil was compared to the treatments. The treatments with neem straw and amaranthus had less apothecia production. ln the field, the effects of irrigation and of the planting density in white mold development in beans were studied. The treatments were spaced among rows at 45 and 75cm and three water applications were supplied to the soil (humid, ideal and dry). The effect of irrigation :frequency and straw presence on the soil on white mold development in beans in two field experiments was also studied. The following treatments were established: irrigation frequencies (3, 7 and 12 days) and presence or absence of com straw on the soil. The humid treatment resulted m a larger number of apothecia and larger incidence of disease. The spacing did not influence these variables. However, the spacing of rows influenced the production of grains with larger production at 70cm. ln the first experiment of irrigation frequency, the treatments with com straw presented a smaller number of apothecia and smaller incidence of disease. The production of grains was not statistically affected by the treatments. In the second experiment the treatments without straw produced more apothecia, although no statistical difference was detected. Toe three-day irrigation frequency favored apothecia formation and the incidence of disease. There was smaller incidence of disease in the treatments with straw and in the treatment with 12 days intervals between irrigations. The presence or absence of straw and irrigation frequency did not have statistical effects in the final production of grains. (AU) | |