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Productivity of the resistant progeny
In our s tudy, w e e valuated pr oductivity, m easured as bi omass and s eed s et p arameters,
without c ompetition be tween co -cultivated ge notypes, w hich c ould correspond t o t he
conditions at the field border (i.e. the cultivated border line that is not sown). In most studies
of t ransgene es cape b etween B. napus and B. r apa, BC 1 and F 2 exhibited l ower s eed
production t han their pa rents [ 6, 9] . In our s tudy, BC1 and F 2 demonstrated s ignificantly
higher ve getative pe rformance t han B. napus , which c ould pr ovide op portunity f or qui ck
establishment at the expense of volunteer and cropped oilseed rape. In contrast, BC1 and F 2
produced less seeds than B. napus, and they had lower seed production efficiency per biomass
unit t han B. napus , ( Fig 2.5), w hich c ould i mpact t heir r eproductive s uccess be cause m ore
resources were needed to produce seeds. The difference of seed production between BC1 and
F2 was bordering significance, because of the effect of the high variance found in BC1, which
probably denoted an effective difference. Especially, the productivity of BC1 per biomass unit
was cl early h igher t han t hat o f F 2 (Fig. 2.5). T herefore, it is lik ely th at B C1 are ab le t o
establish in waste areas, field borders, and even arable fields, more easily and rapidly than F2
plants. The low variability noted for B. napus in the regression function between seed number
and biomass was of environmental nature only because the cv. Drakkar is a pure line, which
suggests that the higher variability recorded in BC1 and F2 could be genetically determined. A
similar case of higher variability of performances was also observed in B. napus and B. rapa
hybrid pr ogeny [ 8], w hich c ould be t he s ource of f urther genetic a daptation a nd l ead t o
successful volunteers o r new w eeds in both non -crop and crop habitats. Such a situation is
highly favorable t o t he r apid e volution of a daptive t raits t o t he a groecosystem [24]. I n
addition, half of the BC1 exhibit the herbicide-resistance, which could help plants to survive
in arable fields and roadsides if the corresponding herbicide were employed.
No d ifference was o bserved b etween r esistant an d s usceptible BC1 plants (BC1NR versus
BC1NS + BC 1NS*) and between resistant and susceptible F 2 plants, which suggests that no
detrimental effect existed for expressing the herbicide-resistance gene. Preliminary data of the
comparison of t he m utant l ine us ed he re w ith i ts or iginal c ultivar s howed th at d elayed
flowering w as r esponsible f or 6 -14 % l ower yield [ 18]. In t wo ot her c ases onl y t he f itness
differential due to ALS-endowed resistance was studied with appropriate plant materials and
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