Shares in Syngenta continued their upward move on Thursday, taking their gains this week above 11%, as JP Morgan became the latest bank to upgrade the stock.

JP Morgan raised its rating on the shares to "overweight" from "neutral", the third major investment bank in four days to release a bullish report on the Swiss agrichemicals group.

Credit Suisse on Monday made a similar ratings revision, while UBS on Wednesday added Syngenta to its "key call" list, with a buy rating and a target price of SFr295.00 for the shares.

Syngenta shares, which ended last week at SFr223.50, closed at SFr248.30, up 3.7% on the day.

Spillover effect

UBS analyst Thomas Gilbert said Syngenta shares had been unfairly punished by investors because of the nine warnings by rivals – three apiece from Monsanto and Nufarm, two from MA Industries and one "cautious" statement from Bayer CropScience – relating to the global glut of the herbicide glyphosphate.

However, Syngenta was only a relatively small player in glyphosphate, with a 7% share of the global market, and was poised to reduce its purchasing costs through a switch from Monsanto to Chinese suppliers.

"Capital markets continue to misunderstand Syngenta's earnings exposure to… glyphosphate," Dr Gilbert said.

Meanwhile price increases in all seed product lines mean that "for the first time in years, Syngenta could demonstrate tangible progress in seeds profitability".

"In 2008 Syngenta was an overpriced growth story," he added.

"It now looks like a more reasonably priced margin expansion/ free cash flow generation story."

Syngenta in July released its own profit warning, saying that annual earnings this year would come in "close to" 2008 levels, rather than seeing the improvement the company had hoped for, thanks to lower wheat acreages and the impact of the credit squeeze on farm spending in Eastern Europe.