“…In the past, researchers considered that it might be governed by the presence of chemicals confined to the phloem (Sogawa and Pathak, 1970). Bph1 was the first BPH resistance gene identified and is associated with the production of flavonoids, including SA; amino acids, such as Asp, Glu, Ala, Ser, Leu, Asn, and Val; and organic acids, such as succinic acid, malic acid, oxalic acid, and transaconitic acid (Sogawa and Pathak, 1970;Sogawa, 1976). There is now considerable evidence to suggest that induced defenses are effective and have low fitness costs.…”