Agriculture Reference
In-Depth Information
Insect
Callosobruchus maculatus
(Coleoptera: Bruchidae) was obtained from a colony
maintained in the Laboratório de Química e Função de Proteínas e Peptídeos from the Centro
de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, Campos dos
Goytacazes, RJ, Brazil. The insects were reared on cowpea seeds (cv. Fradinho) at 28 °C, 60-
80 % r.h., and a photoperiod of L12:D12.
Seed Coat Thickness, Texture and Coloration
The seeds of cowpea (cv. Fradinho) and soybean (commercial seeds and Conquista,
UFV-20 Florestal, UFUS 2003, UFUS 2005, Tucunaré, Elite cultivars) were de-coated and
the thickness of 3 randomly chosen seed coat fragments were measured by an electronic
digital Marathon micrometer (0-25 mm measuring range). The seed coats pigmentation and
texture were analyzed through observation under a stereoscopic microscope coupled to a
digital CCD video camera. The results were analyzed through Student's
t
test, and significant
differences were determined at
P
< 0.05 (Bridge & Sawilowsky, 1999).
Natural Soybean Seeds Experiments
Sixty natural soybean seeds from commercial line or from the Conquista, UFV-20,
Florestal, UFUS 2003, UFUS 2005, Tucunaré and Elite cultivars, placed into glass flasks,
were exposed to ten
C. maculatus
females (of 3-days-old) during 24 h, inside a BOD
incubator chamber, at 28 °C and 70% r.h. After this time, the females were removed and the
eggs laid on the seeds were counted. After 8 and 12 days of incubation at 28 °C, 70% r.h., the
larval eclosion was observed and registered and the seeds were incubated for other additional
28 days, in the same previous conditions. Adult emergence was evaluated after the whole 40
days-period. The larval development was accompanied throughout the period, by daily
observations with a stereoscopic microscope coupled to a digital CCD video camera, since the
posture day (first day after oviposition) until the complete perforation of the seed coat or until
larval death. The necessary time (days) for the surviving larvae to perforate the seed coat
completely was also observed. Control experiments using cowpea host seeds were performed
at the same above described conditions. The results were analyzed through Student's
t
test,
and significant differences were determined at
P
< 0.05 (Bridge and Sawilowsky, 1999).
Artificial Cowpea Seeds Covered with Natural Soybean Seed Coats
Experiments
Seed coat pieces were separated from cotyledons and the effectiveness of these tissues as
barriers against the penetration of the C. maculatus larvae was studied by using an artificial
seed system (Macedo et al. 1993), modified by us to include a covering piece made of natural
soybean seed coat (Figure 6A'). Artificial seeds (final mass of 400 mg) were made by using a
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