Discovery of Sikkim Primitive precursor in the Americas

Till now, it has been thought that the legendary landrace Sikkim Primitive (SP) discovered by N. L. Dhawan (MNL 38:69-70, 1964) is distributed only in the remote pockets of North-Eastern Himalayas (NEH). Because of its ear morphology, which has remarkable resemblance to pre-historic wild maize, it has aroused enormous interest among the crop plant evolutionists. Many speculations have been made about its origin and interrelationships with the established races of maize. P. C. Mangelsdorf (In Corn, its Origin, Evolution and Improvement, 1974) assigned it to the lineage of Palomero Toluqueno, an ancient indigenous race of Mexico. H. G. Wilkes (MNL 55:13-15, 1981; MNL 56:27-28, 1982) considered it a derivative of ladyfinger popcorn. Some others, however, did not attach any significance to the potentialities of SP maize.

The problem faced by scientists in identifying SP type of maize in the Western hemisphere is due to three reasons: (1) That the descriptions of the plant types of Sikkim Primitive given by N. L. Dhawan (MNL 38:69-70, 1964), D. Gupta and H. K. Jain (MNL 45:37-39, 1971) and Bhag Singh (In Races of Maize in India, I. C. A. R. Publ., 1977) do not provide full and accurate information. The studies made by these authors suffer serious drawbacks. The climate to which SP maize is adapted is somewhat akin to temperate zones. The SP maize grows in high hills of NEH in a humid and cooler environment. These authors have collected samples of SP maize from the altitude of 4000-6000 feet and directly grown them under the severe stress conditions in the extreme tropical summers at Delhi, where the mercury touches 45 C during the growth period of maize. As a result, the architecture of Sikkim Primitive plant was drastically altered, and the data based on such studies have led to erroneous conclusions and confusing speculations. (2) The second factor has been the strict U.S. quarantine laws, banning the entry of outside maize into the U.S.A., and (3) frustration of scientists not to have access to the natural habitat of SPs and expressing their views based on inadequate information, without accepting the truth that SP plant type still maintains its distinctive features of pre-historic wild maize (see J. K. S. Sachan and K. R. Sarkar, MNL 56:122-124, 1982).

A pragmatic and convincing view on the origin of Sikkim Primitives was conceived by Nobel Laureate, George W. Beadle, who in his personal communication to one of us, in 1978, emphasized that Sikkim Primitive plant type can be synthesized from the existing variability in Zea. We had been pondering over the question of antiquity of maize in India, especially of SP maize. After studying the knob heterochromatin distribution of SP maize, which is comparable to present day Nal-Tel, we were convinced that there must be a precursor or derivative of SP type of maize in the Western hemisphere. Now we feel that SP maize has its precursor in the Americas (see Figure). W. L. Brown's illustration of a prolific maize variety from South America (Proc. 20th Annual Hybrid Corn Ind. Res. Conf., 1965, p. 8) bears a striking resemblance to the Sikkim Primitive strains and in our view SP maize is closely related to this variety, probably both sharing a common ancestry. The illustrated plant encompasses all the characteristic features of Sikkim Primitive maize, namely, (1) prolificacy, (2) high placement of ear on the stalk, (3) upper ears terminating in a male spike, (4) popcorn type, (5) small ears, (6) uniform size of ears, (7) central spike of tassel bent, (8) gynoecious stalks and (9) tillering (see J. K. S. Sachan and K. R. Sarkar, MNL 56:122-124, 1982).

The evidences gathered from the archaeological studies of the specimens and vegetal remains from Mexican Caves, namely, Bat Cave, Romero's Cave, Swallow Cave, Coxcatlan Cave, El Riego Cave, and San Marcos Cave, dating back to 2000-5000 B.C., amply suggest that the living fossil of pre-historic wild maize, which is considered as progenitor of both Nal-Tel and Chapalote races, is well preserved in the form of 'Sikkim Primitive' in the isolated pockets of NEH. The botanical characteristics of pre-historic maize (see P. C. Mangelsdorf, in Corn, its Origin, Evolution and Improvement, 1974) are exactly the same as that of Sikkim Primitive maize, viz., (1) prolific nature, (2) ear placement high upon stalk, (3) uniformity in the size of ears, (4) upper ears terminating into male spike, (5) popcorn type, (6) small and slender ear with 8-10 irregular rows, (7) cylindrical ears, (8) soft rachis, (9) soft papery glumes, and (10) tillering potential.

Therefore, it seems that SP maize and NalTel/Chapalote have evolved from the same common ancestor, the pre-historic wild maize.

Figure: W. L. Brown's illustration of a prolific variety from South America, presumably precursor of Sikkim Primitive maize (see text).

J. K. S. Sachan and K. R. Sarkar

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