INFLUENCE OF THE SOYBEAN SEED COAT UPON SEED INFESTATION AND DEVELOPMENT OF THE INSECT CALLOSOBRUCHUS MACULATUS - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 7

finely ground decorticated cowpea seed meal, from an insect susceptible Vigna unguiculata
genotype (cv. Fradinho). 50 mg of the flour of V. unguiculata was placed into a cylindrical
brass mould and over that powder a piece of natural seed coat, with the external part of the
seed coat facing down, was laid. Later, 400 mg of V. unguiculata flour were added over the
seed coat piece. The artificial seed was made by pressing the mixture with the help of a hand
press, and after removal of the seed from the mould, the V. unguiculata flour excess (50 mg)
was removed from the outer surface to expose the piece of seed coat (Figure 6A'). The parts
of the artificial seed that were not covered by the seed coat fragment were protected with a
plastic film and the seeds were presented to fertilized females in glass vials. Three females (3-
days-old) were transferred to each vial (two seeds per vial) and kept inside it for 24 h at 28
°C, at 70% r.h. After this time, the females and the excess of eggs were removed; three eggs
laid on the piece of seed coat were left per seed. After 8 days of incubation at 28 °C, at 70%
r.h., the larval eclosion was observed and recorded. After completion of 20 incubation days,
larvae that crossed the seed coat or died inside the eggs were counted. The seeds were opened
and the weights of all larvae were taken and compared with larvae grown in control artificial
cowpea seeds. Experiments were run in triplicate (total of 9 eggs). These 9 eggs laid on seed
coats were considered as 100 % when calculating the percentages of larval eclosion, larva that
crossed the seed coat and larvae that died inside the eggs. Control seeds consisted of artificial
cowpea seeds covered by a cowpea seed coat fragment, manufactured identically as above
described.
Figure 1. Performance and survival of Callosobruchus maculatus on natural host Vigna unguiculata
seeds (positive control) and Glycine max seeds (cvs. Tucunaré, Elite, Conquista, UFV-20 Florestal,
UFUS 2003, UFUS 2005 and commercial soybeans). Data refer to the infestation of sixty seeds from
each species by ten C. maculatus females.