Nov. 10 (Bloomberg) -- Monsanto Co., reeling from its first market-share losses to DuPont Co. in a decade, may be losing the confidence of some investors based on early results from the new modified seeds it's counting on to beat competitors.

DuPont, the second-biggest seed maker, grabbed U.S. sales from Monsanto this year, showing its larger rival that farmers won't always pay for the most advanced seeds. Monsanto aims to regain market share with corn that contains eight genetic changes and the first update of its herbicide-resistant soybeans in 13 years.

Monsanto Chief Executive Officer Hugh Grant is counting on the new soy and corn varieties to add $1 billion to profit by 2012. A survey of growers early in the harvest now under way indicates the seeds aren't meeting yield expectations, contributing to an 11 percent decline in Monsanto's shares the week the results were circulated.

"The distrust that could be building in the market is very negative for Monsanto," Paul Baiocchi, a senior market strategist at Delta Global Advisors, which manages $1.5 billion, including Monsanto shares, said in a telephone interview from San Francisco.