Mycorrhiza are probiotic bacteria, essential for the transformation of organic minerals to organic forms that can be metabolised by plants, without which the inorganic minerals stay bound in the soil and unavailable to plant life. Less probiotic bacteria = less minerals available to plants = less nutrients in the foods we and our livestock eat.
Plants that are grown with herbicides and pesticides have no need to produce protective compounds themselves. These flavonoids and carotenoids not only protect the plant from disease, UV light and other damage, but have the same beneficial action in our bodies when we eat them. Not only do we eat less of these protective plants, but the plants themselves have a lower content of protective nutrients. Organic plants, grown without pesticides and herbicides, do need to protect themselves, and therefore produce higher levels of flavonoids and carotenoids. This is one area where organic is most definitely best.
The desire for all-year-round (out of season) fruit is met by early picking, cold storage and rapid ripening in ethylene gas. Such fruit does not have a fully-developed nutrient potential, and storage depletes the vitamin content.