Seed production of recently established weeds in semi-dwarf oilseed rape cultivars

Peters, K., Porembski, S., Gerowitt, B.

15th European Weed Research Symposium

Seite: 1 - 1
Jahr: 2010

Institut: Professur Phytomedizin

Over the last decade, there has been an increase in the number of weeds in oilseed rape. Especially in the north-eastern part of Germany Anchusa arvensis (L.) M. Bieb., Sisymbrium officinale (L.) Scop. and several Geranium species recently became very important weeds in oilseed rape and are gaining importance in other German regions as well. To study the development, seed and biomass production they were planted into different oilseed rape variety stands.
Recently semi-dwarf oilseed rape varieties appeared in practical cropping. So far only few studies focused on the properties of different oilseed rape varieties in combination with weeds. Here, three cultivars of semi-dwarf oilseed rape differing in plant height were chosen for contrasting purposes: The normal growing variety “Viking”, the semi-dwarf variety “PR45D01” and a full dwarf rape biotype that is only used for breeding purposes. All varieties were sown at identical seeding rate in a field, arranged in randomized plots of two rows. Weed seedlings raised in a greenhouse were planted directly into the plot at six-leaf stadium (BBCH 16) of oilseed rape. Seed and biomass production were measured directly before harvest.
S. officinale produced more biomass and seeds per plant in semi-dwarf than in normal oilseed rape. It avoided growing below the canopy of oilseed rape of normal height by increasing dilatation growth to gather more light. Generally, S. officinale shows rapid growth and sometimes overgrows even regular oilseed rape varieties. There it also produced fewer pods, but those contained more seeds, namely 12 vs. 11 per pod. Total weed seed production was about 2775 seeds per plant in the normal height variety and 4410 in semi-dwarf rape.
A. arvensis seems to be only capable of growing larger than semi-dwarf oilseed rape. In normal rape the plants were smaller, had lesser side shoots, showed a lower biomass production and produced less seeds. One plant produced about 240 seeds in semi-dwarf rape vs. ~ 450 in rape with normal height.
In all rape varieties the three Geranium species produced nearly the same amount of seeds (~ 625 seeds per plant) and showed little differences in biomass.
In contrast to conventional oilseed rape, infestation of high growing weeds is more probable in semi-dwarf oilseed rape varieties. The light-indigently S. officinale and A. arvensis show increased biomass production and higher seed production per plant in semi-dwarf oilseed rape and certainly having high ability for competition. Geranium species employ a different strategy to deal with low light intensity conditions. They are half-shade specialists and are insensitive to the growing habit of the crop. Only at high densities during the leaf stadium of oilseed rape could they cause substantial yield losses.




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