Although I am concerned primarily with corn breeding, I have started genetical studies of corn grown in Puerto Rico. There are many mutants found in local corn, such as white and yellow seedlings, various other chlorophyl deficiencies, male and female sterility, narrow leaf, tassel seeds, vivipary, brown midrib, red pericarp, variegated pericarp, and others. Whether these mutants have been introduced from the North, and subsequently incorporated into local corn, or are local in origin it is difficult to tell with certainty. However, it is well known that corn from the mainland is not adaptable to local conditions, and the few attempts to introduce it to Puerto Rico have failed. The corn imported from other regions, such as Santo Domingo, Cuba and Argentine is used exclusively for feed.
Many crosses were made between some of these mutants and unrelated stocks, and F2's and backcrosses are expected to be raised this spring. For the present I want to mention two interesting cases; brown midrib and tassels, and forked or split stem.
Brown midrib and tassels. The F1 data suggest that we have a new dominant mutant, tentatively designated Bm-b, for the development of brown pigment in midrib and tassels. The color appears rather late, before tasseling, and varies in intensity especially in tassels, sometimes approaching color of tassels of a B Pl plants.
This mutant was found in one of the inbred lines. Bm-b plants were selfed and crossed to three unrelated stocks. The selfed plants had also red pericarp and cob. The five F1 crosses segregated in the following ratio:
|Bm-b Pvv||Bm-b p||bm-b Pvv||bm-b p|
The result suggests that Bm-b is closely linked with P. The presence of the red pericarp in Bm-b plants, as well as the development of anthocyanin in seedlings of all F1 plants indicate that the development of brown color in tassels and midrib is not due to a. Also there is evidence that we are dealing with red and not cherry pericarp, as there is no Pl involved in these crosses.
Forked or split stem. A number of plants were observed in several cultures in which the stem is split or forked. The forking may occur in any node. If forking takes place at the node below the ear, then two ears and tassels are formed.
From two selfed forked ears 44 plants were raised, all of which were normal, non forked. The F1 between forked and normal plants yielded:
G. A. Lebedeff