Genus shares, which have lost 19% in three weeks, could face a fresh round of selling if they drop below their 21-month low, an analyst has warned.
The 14p fall to 514p in the livestock semen group's shares on Tuesday left them within sight of 510.5p, their lowest point since August 2007.
"If they go below that, they could fall an awful lot further," said Mick Cooper, an analyst at London-based Blue Oar Securities, who has a "buy" rating on Genus stock.
"It's a technical point. But for some people, that's important."
However, the shares were likely to face support at 500p, he added.
One of the issues Genus has lies in justifying its relatively high rating, Mr Cooper added. The group trades on a multiple of 14 times earnings for the year to the end of June compared with an average of less than 10 for London stocks.
"There's lots of bad news out there, like the UK dairy co-operative [Dairy Farmers of Britain] going down," he told Agrimoney.com.
Evolution Securities, a rival broker, cut its estimate on Genus stock from "buy" to "reduce" last week, citing concerns that "support for the shares may falter as [earnings] growth slows significantly in 2010".
However, Mr Cooper said that Genus's core clients - larger agricultural concerns - remained in relatively good health despite firm feed costs and the low prices of many products, such as dairy.
"It is the mom and pop operations which are suffering most," he said, adding that China remained a promising market.
Genus stock peaked at 894.5p in May last year.
By Mike Verdin