2. Short‑plant types.

A number of apperent mutations to short‑plant types have been collected during the past ten years. Several appear to represent types not previously described, and some have given indications of potential value as breeding material. None of the types so far collected can be considered "dwarfs", in the maize genetics terminology commonly used. The most conspicuous feature of all our stocks is a marked shortening of the internodes, particularly of those below the ear‑bearing mode. Node number is little, if any, different from that of normal types.

Three of the short‑plant types, received from widely separated hybrid seed corn producers, have been shown by F₁ and F₂ data to have the same major internode‑shortening gene. One of these types ("Oakes dwarf") has been described previously (Maize News Letter 15:29. 1941) and its "dwarfing" gene may be located on chromsome 3 (Maize News Letter 16:21. 1942). Data from F₁ and F₂ indicate that the gene involved is not d₁.

Certain crosses between the types carrying the same major shortening gene have produced ears nearly as large as those of standard hybrids on plants which are 45 to 55 inches tall (to base of tassel). Some of these types may have promise in the breeding program. Several approaches to their use are being attempted.

Other short‑plant stocks differ from the "Oakes dwarf" group in genes affecting internode length. F₂ data from several crosses between these and the "Oakes dwarf" group suggest 9:3:4 segregations, but the different short‑plant segregates cannot readily be distinguished from each other. A number of other stocks, mostly mutant types found in standard inbred lines, are now under test to identify the genes involved. Brachytic stocks and Singleton's C 30 (reduced) are also being included in these tests. There appears to be a need for a comprehensive survey and analysis of the various short, midget, miniature, reduced, and dwarf types to clarify the genetic relationships involved, and some revision of terminology may be necessary.

Earl R. Leng and

C. M. Woodworth