| The following seven morphological characters were studied in the selected
plants; length of the longest internode of the rachis, length of the spike,
difference in lengths of the peduncle and sheath (of the flag leaf), number
of undeveloped spikelets, length-width ratio of the lower glume, and the
number of ridges on the glumes. Pictorialized scatter diagrams were prepared
by the length of the longest internode of the rachis and the length of the
spike as the ordinate and abscissa respectively. Hybrid indices for forty
plants were prepared by the technique devised by Anderson (1949, 1957).
Character association analysis for the seven morphological characters indicated that these characters were associated in two well defined groups, as described below; (a) Wheat like : - The following combination of characters was observed; short rachis internodes, short spikes, peduncle much longer than the sheath of the flag leaf, several undeveloped spikelets, low length-width ratio of the lower glume, and few ridges on the glumes. (b) Grass like : - The following combination of characters was observed; long rachis internodes, long spikes, peduncle equal in length or shorter than the sheath of the flag leaf, few or no undeveloped spikelets, longer and less broder glumes, and the presence of several ridges on the lower glumes. Besides these two distinct types, there were several plants which represented varying recombinations of the characters of the two extreme types. The variation pattern of the material seemed to be discordant (Anderson, 1951), which is characteristic of strongly introgressed populations. The loose association between the seven characters and the recombinations between some of them could be explained by assuming hybridization, segregation and subsequent introgression between the species of the genera Triticum and Agropyron. An analysis of the hybrid indices revealed that a few of the plants were grass-like, but majority of them were wheat-like. It would, thus, seem more likely that the introgression is from Agropyron into Triticum. The utilization of the pictorialized scatter diagram method, in studying the variation of wheat x wheat-grass hybrids seems significant. With the use of even such a small sample, by using comparative characters and hybrid indices, the relative amount of variation could be approximately ascertained. |
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