Relationship between "reversed germ" (r.g.), kernel weight, and number of rows of the ears

In MGCNL 30:84-85, Gertrud Joachim reported a study on mutants of maize which produced a variable proportion of kernels with reversed germ ("r.g.") disposition. In corn, two spikelet primordia develop into one upper and one lower floret each. Usually, the lower floret aborts in early primordia development and only the upper one develops into a mature kernel. The interpretation was that, if the abortion of the lower floret did not occur, its development originated a "reversed germ" kernel. This situation could have originated two kernels per spikelet, with a mirror image symmetrical disposition or only one kernel (which was "r.g.") per spikelet, if the upper floret aborted. The character "r.g." could be assigned to three recessive genes, each one of them, by itself, determined a variable proportion of kernels with "r.g.," but the expressivity never reached 100%. The inheritance of the character was found to be maternal.

In the backcrossing process of an opaque-2 flint inbred, plants with the character "r.g." were observed in the segregating offspring of two selfed plants. These two plants were sisters from selfing. From the study of the segregation, concordance was found with Joachim's conclusions. In addition can be reported: a) In our stock the proportion of "r.g." kernels is greater. In fact, from 41 ears studied, 10 had "r.g." kernels, seven of them with 100% "r.g." kernels, and three with proportions of 70.3, 87.6 and 96.7%; b) the ears with "r.g." kernels had a number of rows significantly less than their normal sisters. The kernels of the ears with "r.g." were significantly greater and denser than the kernels of normal ears. However, no difference was found between normal and "r.g." kernels from the same ear. Tests for allelism with the materials studied by Joachim have not been done.
 
      Row No. Weight of kernels
Ear Total

Ears

Ears with

"r.g." (%)

Ears with

"r.g."

Normal

ears

Diff. Ears with

"r.g."

Normal

ears

Diff.
1 20 5 (25) 13.6 16.61 3.01**      
2 21 5 (23.8) 13.2 16.12 2.92**      
Total 41 10 (24.4) 13.4 16.34 2.96*** 0.31 0.27 0.04*

*p < 0.05; **p < 0.01; ***p < 0.001

Mariano Blanco, Angel Alvarez, Luis Bosch and José L. Blanco


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