Robertas still top of the fully recommended
FULLY recommended list varieties are at least 2% lower yielding than the best of the provisional group.
Roberta, on the list since 1993 and the current standard, offers good establishment, low bolting, and good yield.
Triumph, listed a year longer, offers relatively poor yield, only 0.5% above Chorus. "It has really been an average performer throughout," says Mr Kerr.
"There is a big push towards early drilling to get a yield benefit, but bolting and capping then become major issues.
"Looking at five years data it would appear that Latoya on the provisional list is potentially a good early sowing and early harvesting variety.
"Stallion is more suited to late drilling and a late harvest."
For early sowing he suggests Roberta is still the number one choice with Latoya a close second.
"Latoya offers sugar yield of 102% making it one of British Sugars favourites. With 86% establishment and good suitability for early or normal drilling due to low bolting, it is a strong contender for next year."
Nowadays the crop is left in the ground longer so growers need to pick varieties with good mildew and rust resistance as well as low bolting, he advises.
"Most growers select two or three to cover early, mid and late drilling," he says. "We suggest going for high root and high sugar types."
For mid season drilling he suggests Sweet and Giovanna. They offer good yields and respectively extremely low and zero bolting at that timing. For later sowings Humber, Stallion and Wildcat get his thumbs up.
Priscilla and Murray will be considered for a move to the fully recommended list next year.
Baron and Jessica have performed more consistently over the years. But with below average establishment it is unlikely that either will become fully recommended.
"Humber, with adjusted yield of 101% and good establishment, has proved popular, despite a poor bolting figure for early sowing. Poor performance in trials last year could affect its chances.
"However if, like Latoya, it continues to yield well, both varieties stand a very high chance of moving up to fully recommended," says Mr Kerr. *
THE trend to earlier drilling means bolting, establishment and disease resistance have become increasingly important selection drivers, says NIABs Simon Kerr.
Sugar yield, a characteristic favoured by British Sugar, also helps growers cut transport costs by reducing the number of loads sent to its factories.
"Seed quality is a big consideration and has a critical impact on performance," adds Mr Kerr. "So growers should choose most of their seed order from the fully recommended group as commercially produced seed lots."
Experimental seed lots, which may contribute to provisional list results, can give less reliable results, he explains.
"Where only breeder seed is being tested, the results do not always provide a true reflection of variety performance in a commercial situation."
NIAB trials allow comparisons between varieties with high root yield and moderate sugar content and those with moderate root yield but high sugar content. But other factors to take into account include establishment levels and bolters.
British Sugar is keen to promote varieties with low amino N in the juice, and breeders selecting on this basis have done well in reducing impurities, says Mr Kerr.
Seed quality has also improved greatly in the past decade. But relative yield differences between recommended varieties are now small, and all on the NIAB list are fairly robust, he notes.