Fifteen UK-led projects will share funding of £12.1m from government and £5.7m from industry.
One aims to improve the taste of lamb while reducing waste, while another seeks to boost the quality of strawberries grown without soil.
Mr Cameron also said that all Whitehall departments would buy locally sourced food wherever possible from 2017.
No-one in Britain worked harder than farmers, he said ahead of a visit to the Royal Welsh Show.
"By opening up these contracts, we can help them create more jobs, invest in their businesses and make sure people in our country have a healthier lifestyle," Mr Cameron said.
"It's a triple-win - and will mean a brighter future for our country."
Other research projects to benefit from the scheme include an investigation of how to protect peas and beans from beetles without widespread insecticide use, and using technology to detect health and welfare problems for pigs earlier.
With the shift on public sector food and drink procurement, the government said it hoped to divert hundreds of millions of pounds from foreign suppliers to UK-based providers.
Environment Secretary Liz Truss said: "This move will mean that food served in canteens across the public sector can be more local, seasonal and tastier.
"This is a huge boost to British farmers and producers and for students, patients and employees who want to enjoy fantastic food."
Details of how £17.8m will be allocated among agricultural research projects have been unveiled by PM David Cameron.