Sikkim Primitive

Last year one of us reported on maize collections made while on sabbatical in India. This laboratory has continued to study the Indian landrace Murli from Sikkim and the Darjeeling region of the Eastern Himalayas. In the literature this landrace has been called Sikkim Primitive because of the resemblance to the reconstructed ancestor of P. C. Mangelsdorf. When collected in Sikkim the ears are small "Ladyfinger-like" specimens. Last year the plants did not flower for us before the killing frost because of their pronounced short day requirements but this year we did bring plants to flower in early September. These plants gave us an ear which is comparable to an eight- to ten-inch commercial open pollinated popcorn. That the small cob and slightly protruding glumes of Sikkim Primitive were not genetically fixed was a surprising finding for us. Sikkim Primitive could have any number of yellow endosperm commercial popcorns as its founder stock. In no way is Sikkim Primitive a long lost ancestral stock of maize, but a phenotypic response to a unique environment with adaptation to short day conditions of the tropics. In an attempt to fingerprint this landrace, we have worked out its knob pattern (see diagram) and would be interested in knowing if this pattern is similar to any commercial yellow endosperm popcorns.

The really interesting finding of this study is reported in the first report. It appears that this local landrace, adapted to a high elevation cloud forest region of the tropics, shows pronounced abnormalities in cell organization when grown under radically different conditions here in Boston (The Waltham Field Station, Waltham). Like most corns or teosintes collected in the tropics this collection possesses a short day photoinduction response. Grown under the long summer days, it failed to flower, but when the day length was shortened it plunged the whole plant from vegetative growth phase to reproductive phase. The suddenness with which this happened has disrupted the timing of cellular processes and we observed in microsporogenesis double nucleoli and abnormal amounts of RNA and DNA. The question is: Can these physiologically induced abnormalities be used as a model for other abnormal cell developments? The hypothesis is that the rapid induction has stressed cell physiology and the response has resulted in increased amounts of RNA and DNA. The timing systems of the cells have in essence become unregulated and therefore abnormal.

We are interested if other researchers have observed similar phenomena when radically changing the environment of maize they have obtained from elsewhere, preferably the short day tropics. Currently, we are investigating the flint maize Tista Mendi grown in the same region to see if it possesses a similar response. This parallel habitat race from the same region should serve as a control to our hypothesis of physiological disruption as the cause of double nucleoli and other abnormalities in microsporogenesis.

Figure.

H. Garrison Wilkes and John Peeters


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