We report that some progeny of crosses between Zea luxurians (Z.l.) and Z. diploperennis (Z.d.) smell like butterscotch. One of us (RMB) first noticed the odor on two F1 plants about to flower in the winter greenhouse at Columbia, MO--the tassels being the source. These plants were transplanted outdoors in the spring where they flowered again with the same odor.

The following winter both plants were shipped to Raleigh, NC. One survived and continues to grow--and to give the strong odor of butterscotch from its tassel at flowering time. This plant (Neuffer 38:704.2) is the product of the cross of Z.l. (Neuffer 36:797-1, accession 759: derivative of USDA seed of Z. luxurians P1306615 collected near El Progresso, Jutiapa, Guatemala) by pollen parent Z.d. (Beckett 7931-1: Guzman 777 [original discovery], ex H. H. Iltis, ex Missouri Botanical Garden, collected at La Ventana, Jalisco, Mexico).

The second of us (SAM) determined by olfactoral examination through several flowerings that a butterscotch odor also exuded from the plant Hybrid #6 of the parentage Z.d. (Modena Mo81043/*100-1 : Guzman 1120, ex H. H. Iltis, collected east of Las Joyas, Jalisco, Mexico) by Z.l. (Modena G-36*6: Iltis G-36, ex H. H. Iltis, collected west of Agua Blanca, Jutiapa, Guatemala). Like the above plant, the tassel odor was strong during flowering. The odor was stronger on the female spikes, leaf blades and especially the leaf sheaths. The plants (clones) were often damp at night or the early morning hours and the perfume was transferred to the hand with a touch. The essence is volatile. The odor was present for several weeks during the fall and the spring flowerings, but not between flowerings nor during the summer.

Several hybrid plants do not have this perfume at all. These are: Hybrid #3 of parentage Z.l. (Modena G-42*2 : Iltis G-42, ex H. H. Iltis, collected north of Ipala, Chiquimula, Guatemala) by Z.d. (Modena Mo81043/*100-3 : Guzman 1120); Hybrid #5 of parentage Z.l. (Modena G-36*3 : Iltis G-36) by Z.d. (Modena Mo81043/*100-3 : Guzman 1120); Hybrid #8 of parentage Z.d. (Modena Mo81043B : Guzman 1120) by Z.l. (Modena G-5*2 : Iltis G-5, ex H. H. Iltis, collected north of El Progresso, Jutiapa, Guatemala); Hybrid #9 of parentage Z.d. (Modena Mo81043A : Guzman 1120) by Z.l. (Modena G-5*1 : Iltis G-5). Neither of us has observed the odor on Z.l. plants, and the clones of the Z.d. parents do not have this odor.

We speculate that the butterscotch odor arises because of a secondary metabolite synthesized in hybrid plants. There may be several steps in the chemical synthesis of this metabolite, but the pathway suffers a synthetic or regulatory genetic block in each species-but at a different point. There may also be variation for several block points since only some combinations of Z.l. and Z.d. complete synthesis of the metabolite.

Robert McK. Bird and Stephen A. Modena
 
 

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