9 November 2001

French like rhizo busting varieties

RHIZOMANIA-tolerant varieties will take over the French sugar beet area within two seasons, visitors to the countrys Sugar Beet Harvesting demonstration near Compiegne in Picardie heard last week.

Similar varieties bred for UK conditions could allow English growers to follow suit just a few years later, claims one of Frances top seed companies.

How quickly English growers adopt such varieties will depend on the importance they place on retaining sugar beet in their rotations, said Francois Desprez, president of breeder Florimond Desprez. He believes they are essential for the crops long-term future.

The company has long bred sugar beet for the French market. But different disease and pest pressures mean it does not currently breed for the UK. Rhizomania could change that.

Florimond Desprez is one of several companies producing tolerant varieties that already account for two-thirds of the French crop. Now they have their sights set on producing varieties to suit the UK.

Standard varieties grown in infected fields in France may yield just 20-30t/ha of harvested beet, against 60-80t/ha from a tolerant or resistant type.

"Without disease present, sensitive varieties still have a little advantage in yield over tolerant varieties," Mr Desprez acknowledged. "But the difference is getting less. In two or three years, there will only be tolerant varieties on the French market and in England maybe another six or seven years."

Many French farmers moved to tolerant types early in anticipation of the imminent spread of rhizomania to their farms, Mr Desprez said. About 40% of the 400,000ha of French beet land is infected. Unlike the UK there is no rhizomania containment policy in France.

Mr Desprez predicted rapid development of new varieties with multiple resistances to diseases other than rhizomania.

Breeders such as Van der Have, which has three new tolerant varieties for the French market, have combined rhizomania tolerance with resistance to rhizoctonia, mildew and nematodes, and have also overcome early problems of high dirt tare in rhizomania-tolerant varieties, he noted &#42

STROBS ON BEET

French growers are leading their English counterparts in having two seasons of experience of using strobilurin fungicide chemistry on sugar beet. Ogam, a combination of kresoxim-methyl and epoxiconazole equivalent to Landmark, is best used as the first T1 spray in a two-spray programme, said Olivier Maillot of BASF. Applied around 15 July it is claimed to control powdery mildew, cercospora leaf spot, ramularia and rust for four weeks until a T2 treatment. BASF trials claim a 16% average yield increase, equivalent to 15t/ha, from applying 0.7 litre/ha.

GENETIC STUDIES

A computer model developed at the French National Agronomy Institute (INRA) could help farmers plot the movement of novel traits from genetically modified varieties into wild species and volunteers. The model being tested by PhD student Mathide Sester at INRA Dijon is similar to one for oilseed rape, which can predict the extent of cross-pollination that will move traits such as herbicide and disease resistance from GM plants into weed species. The Genesys-Betterave model uses variety, growth and climate information to assess the risk of cross-pollination and warn farmers of potential weed control difficulties.

STROBS ON BEET

French growers are leading their English counterparts in having two seasons of experience of using strobilurin fungicide chemistry on sugar beet. Ogam, a combination of kresoxim-methyl and epoxiconazole equivalent to Landmark, is best used as the first T1 spray in a two-spray programme, said Olivier Maillot of BASF. Applied around 15 July it is claimed to control powdery mildew, cercospora leaf spot, ramularia and rust for four weeks until a T2 treatment. BASF trials claim a 16% average yield increase, equivalent to 15t/ha, from applying 0.7 litre/ha.

GENETIC STUDIES

A computer model developed at the French National Agronomy Institute (INRA) could help farmers plot the movement of novel traits from genetically modified varieties into wild species and volunteers. The model being tested by PhD student Mathide Sester at INRA Dijon is similar to one for oilseed rape, which can predict the extent of cross-pollination that will move traits such as herbicide and disease resistance from GM plants into weed species. The Genesys-Betterave model uses variety, growth and climate information to assess the risk of cross-pollination and warn farmers of potential weed control difficulties.