The members of the commission shall be natural persons, each of whom shall be a citizen and resident of this state over the age of 25 years, and each of whom, as an individual, partner or employee of a producer or producers, is and has been actively engaged in growing fresh grapes within this state for a period of at least five years and is producing grapes subject to the provisions of this chapter at the time of the election. Not more than two members shall be persons employed by, or connected in a proprietary capacity with, the same corporation, firm, partnership, association or business organization; provided further, that not more than one member in any one district shall be so employed or connected. The qualifications of members of the commission, as herein set forth, must continue during their term of office.