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Show More yield brings problem between the second and third internodes. Each plant's resistance to the disease organisms is evaluated at harvest time. The general health of the stalks is determined by pushing in the sidewalls or, splitting the stalks to evaluate resistance. Evaluation of the rind indicates its strength relative to supporting the plant in an upright position. Healthy ap pearing plants could still possess poor rind quality. During the pollination period a rind penetrometer is pushed into the stalk to determine deter-mine the strength of the rind by measuring its thickness. The gauge indicates the amount of pressure required to penetrate the rind; the greater the pressure, the thicker the rind. A crushing device is also available : for this par-, ticular evaluation. "Another equally important trait", says Dr. Hornbrook, "is the depth or intensity of green coloring in the stalk." This trait is evaluated at harvest time. A deep green color indicates good health. Excessive fading could indicate a weakness that might cause the plant to topple. However, a good, thick rind would tend to minimize this condition. By JUSTIN SCHARFF Increasing the yield of an experimental corn variety is an outstanding achievement for a corn breeder. Once this has been accomplished you might think the breeder would want to go out and celebrate. "Unfortunately, it doesn't work out that way", says Dr. Bert Hornbrook, research scientist for Funk Seeds International of ' Bloomington, Illinois. "It just creates additional problems." "Increased yield", Dr. Hornbrook advised, "requires making the stalks stronger to support the additional weight. Then you have to strenthen the root system and build greater resistance to root worm and larvae. And along the way stalk rot resistance may have to be improved." "Success in breeding a high yield potential", Dr. Hornbrook summerized, "actually opens up a whole new complex of problems." You get some idea of what a a corn breeder is up against by tracing the development of G-4574, a new hybrid silage corn, recently introduced by Dr. Hornbrook and Dr. Rodney Edmundson. G-4574 is a 3-way cross which means its parentage includes three separate in-bred lines. Although the first line was made available in February, 1964, the original development work started in the early 1950's. The second line was completed in 1966 and the third line in April, 1972. The major traits desired for and bred into G-4574 included high grain yield, vigor, large, girthy ears, comparatively com-paratively large kernels, high bushel weight, good height, upright growing leaves, good stalk quality, top tonnage potential and better than average root strength. Dr. Hornbrook believes that during the past few years the most significant advances in corn' breeding, have focused on developing improved insect and disease resistance-factors resistance-factors that exercise a profound effect on yield and standability. Progress in breeding improved varieties is indicated by Dr. Horn-brook's Horn-brook's statement that "today the gene that carries resistance to Northern leaf blight is routinely bred into all varieties compared to 15 years ago when very few hybrids had this gene." Incorporating just a single trait in a new variety can be a monumental undertaking. un-dertaking. Here, for example, are a few of the breeding procedures required for improving just one trait: stalk quality. The program starts when Dr. Hornbrook selects a promising experimental ex-perimental which, although possessing several desireable traits, is .. weak in stalk quality. His first project focuses on selecting other plants with superior stalk quality which will provide the germ plasm for "beefing up" his, original selections. Dr. Hornbrook then proceeds on a program designed to "mix up" the genes by cross breeding. The resulting crosses are :. subjected to tedious and painstaking evaluation until plants with the desired traits are obtained. One procedure involves inoculating the stalks of the plants shortly after pollination ' with five separate stalk rot organisms. An inoculating needle is used to penetrate the stalk jf" f""f"7 7?rT ' tfK'fl 7 K?K" T KT'-h ' Dr. Bert Hornbrook, research scientist for Funk Seeds International, In-ternational, Bloomington, Illinois, evaluates large, girthy ears of G-4574, a new silage corn variety he developed for western growing conditions. |