Why is fruit blessed on Transfiguration?

In the Bulgakov Handbook for servers it states: On the feast of Transfiguration grapes are blessed, and in those places in [such as] Russia where grapes do not grow apples (or other fruit) are blessed. The custom to offer fruit at an appropriate time is undoubtedly ancient, and in the Christian Church is partly the continuation of a similar custom in the Old Testament Church (Gen. 4:2-4; Ex. 13:23; Num. 15:19-21; Deut.8:14) and partly an apostolic establishment (1 Cor. 16:27). Writing concerning this custom is already mentioned in canon 3 of the Apostolic Canons (compare canon 46 of Carthage and canon 28 of the 6th Ecumenical Council). The simple establishment of the custom to offer fruit (grapes) on August 6 is that in Greece fruit are ripe by this time, most of which are new ears of grain and grapes, which are offered for blessing as a sign of thanksgiving for the acceptance of these fruits in the livelihood of man. St. John Chrysostom teaches: “the farmer receives fruits from the earth not so much from his labor and diligence but as much from the grace of God returning these; for “it is neither the planting nor the watering, but that God nurtures”. Besides grapes are brought to the church for blessing because it is directly connected to the Mystery of the Eucharist. According to the Rudder [Book of Canons], “clusters of grapes more any other vegetable are more tolerably brought into church; inasmuch as wine is made from them, the fulfillment of the bloodless sacrifice is understandable”. Similarly and in the prayer “in the partaking of clusters of grapes” the priest prays: “Bless, O Lord, this new fruit of the vine, through the healthfulness of the air, by rain showers and temperate weather, Thou art well- pleased to attain ripeness at this time. May our partaking of this birth of the vine be for gladness and for offering Thee a gift for the cleansing of sins through the sacred and holy Body of Thy Christ”. Apples (and other fruit), itself substituting for grapes, are blessed with another prayer as only the first fruits of vegetables. A more special meaning of the sanctification of fruit on the 6th day of August can be deduced by the general reasoning of the Church that the event of the transfiguration pleasing to the Lord was to show the new situation in which human flesh enters into the resurrection of the Lord and enters into the general resurrection of all believers. But as all nature became subject to God together with man for the last sin, so together with him she also waits for her renewal from the blessing of9God. From here the church blessing of fruit makes man worthy of faith in this hope .