* Viterra offer values ABB Grain at about A$1.6 bln

* ABB directors approve deal

* ABB shareholders to vote in September

* Viterra would gain access to Asia growth markets

* Viterra shares rose 2.9 pct, ABB up 7.8 pct

(Adds credit rating analyst, farmer comment, share price)

(All figures in U.S. dollars unless noted)

SASKATOON, Saskatchewan, May 19 (Reuters) - Viterra Inc (VT.TO: Quote, Profile, Research), Canada's top grain handler, has agreed to buy Australia's ABB Grain Ltd (ABB.AX: Quote, Profile, Research) in a $1.2 billion share and cash deal, giving Viterra better access to Asian markets.

Viterra's (VT.TO: Quote, Profile, Research) proposed acquisition would add "meaningfully" to earnings in the first year, the company said on Tuesday, and could bring synergies of about A$30 million ($23.3 million) a year. Job cuts are not expected.