Karyotypic comparison between maize and its wild relatives

In order to compare the basic karyotype of maize with that of teosinte, Coix, Trilobachne, Chionachne and Manisuris, mitotic metaphase studies were carried out with conventional Feulgen procedure in growing root tips. The basic data on chromosomal types and form percent (Table 1), arm ratio (Table 2), and relative length (Table 3) are presented in the tables.

Both maize and teosinte have shown similar karyotypes. All maize races showed 2n=20, with almost similar total form percent (T.F.%). Variation in arm ratio fell in the range of 6.40 to 3.37. Both teosinte species, Zea mexicana and Zea luxurians, showed similar karyotypes with arm ratio variability of 1.20 to 2.74 and similar T.F.%. Both maize and teosinte had chromosome 6 satellited.

Among the oriental genera of Maydeae, Coix species revealed a lot of intra- and interspecific variations. Coix aquatica had 2n=10, whereas both the cultivated and wild forms of Coix lacryma-jobi had 2n=20 counts. Coix aquatica showed two pairs of satellites, one each on chromosomes 1 and 2. Wild Coix had three pairs of satellites on chromosomes 1, 4 and 5. The short arm of chromosome 1 exhibited two tandem satellites. The cultivated Coix had only one pair of satellites, on chromosome 1. The relative length was largest in Coix aquatica followed by wild and cultivated Coix. The T.F.% of Coix aquatica came closer to that of the wild form and differed from the cultivated form.

Trilobachne cookei gave a bimodal karyotype with 2n=20 having 12 telocentric, four metacentric and four submetacentric chromosomes. Arm ratio varied greatly, from 1.09 to 7.51. Chionachne koenigii too showed a 2n=20 karyotype with 18 submetacentric and two metacentric chromo somes, indicating a highly symmetrical karyotype. Both Trilobachne and Chionachne showed chromosome 5 as satellited.

Thus, clearcut basic differences in karyotypes between the American and oriental genera of Maydeae are indicated.

Table 1.

Table 2.

Table 3.

V. V. Shenoy, J. K. S. Sachan and K. R. Sarkar

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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