Contents - Faperta

414 Biotechnological Approaches for Pest Management and Ecological Sustainability
(Bottraud et al., 1992). However, examination of plants intermediate between S. italica
and S. viridis (L.) Beauv., collected from two fi elds in Maine et Loire on which S. italica
was cultivated, revealed differences in the EcoR1 patterns of chloroplast DNA between
cultivated and wild plants, indicating that reciprocal crosses occur in the fi eld. The results
suggested that even a largely self-pollinated cultivated species at times may exchange
genetic information with wild relatives at rates that may cause problems if transgenic
cultivars are released.
Brassicas
Genes from the conventionally bred Brassica napus L. have been moving to the wild turnip,
B. rapa L. (Raybould and Gray, 1993). Transgenic herbicide tolerance is capable of introgressing
into populations of B. rapa and persisting, even in the absence of selection due to
herbicide application (Snow and Jorgensen, 1999). However, there were no signifi cant
differences between transgenic and nontransgenic plants in survival or the number of
seeds per plant, indicating that fi tness costs associated with the transgene are likely to be
negligible. Pollen fertility and seed production of BC3 plants were as great as those of
B. rapa raised in the same growth rooms. Microscopic studies have shown polymorphism
within the population of hoary mustard for pollen germination on oilseed rape fl owers
(Lefol, Fleury, and Darmency, 1996). The transgenic herbicide-resistant and a commercial
oilseed rape cultivar did not differ in pollen behavior and ovule fertilization. Pollen tube
growth was slow and erratic in interspecifi c crosses. Fertilization effi ciency of oilseed rape,
B. napus in relation to interspecifi c gene fl ow with hoary mustard, Hirschfeldia incana (L.)
Lagreze-Fossat crosses was 15% and 1.3%, respectively, of that in intraspecifi c crosses. There
were no post-zygotic barriers to the development of hybrid embryos in hoary mustard pods.
Up to 26 spontaneous hybrids per male-sterile oilseed rape plant and one per hoary mustard
plant were obtained in fi eld experiments. All hybrids were triploid, with 26 chromosomes,
and had low fertility. They produced 0.5 seeds per plant after spontaneous backcrossing with
hoary mustard. Some of these descendants were produced from unreduced gametes. The
results suggested that gene fl ow is likely to occur, but its actual frequency under crop growing
conditions remains to be estimated. Outcrossing studies have also revealed high potential
of transgenic pollen transfer from rape to B. juncea (Saure et al., 2003). The backcross
progenies with oilseed rape, B. napus var. oleifera cytoplasm (OBC) have a fi tness value 100
times lower than that of the backcross with wild radish, Raphanus raphanistrum L. cytoplasm
(RBC) (Gueritaine et al., 2002). The herbicide-resistant RBC has similar growth to the
susceptible RBC, but fi nal male and female fi tness values were two times lower. In turn,
susceptible RBC exhibited similar fi tness to the control wild radishes, and the relative fi tness
of the different types is the same, whether or not they grow under competitive conditions.
Soybean
The seedlings gathered from seeds from individual plants of a wild accession have been
used for isozyme analysis to identify whether they were hybrids or not. In 23 plants of
the wild accession, four plants produced hybrids (incidence of hybridization 17.4%)
(Nakayama and Yamaguchi, 2002). There was no specifi c direction in hybridization. The
hybridization rate per maternal plant varied from 0 to 5.89% with a mean of 0.73% for all
maternal plants. The results indicated that natural hybrids are easily produced in a certain
frequency by pollen fl ow from the cultivated soybean to the wild soybean when they fl owered
simultaneously, and there was adequate pollinator population.