PHENOTYPIC RECURRENT SELECTION FOR INCREASED ENDOSPERM HARDNESS 2 HIGH-LYSINE MAIZE SYNTHETICS

The agronomic problems associated with high lysine opague-2 maize (Zea mays L.) could be eliminated with the development of opaque-2 genotyp es with harder endosperm texture. Two opaque-2 maize synthetics Illino is Disease Oil Opaque-2 and Illinois Elite Single Cross Opaque-2 were selected for increased endosperm modification or kernel hardness. Phen otypic recurrent selection was used to select for increased endosperm modification for five cycles. Seed from 200 individual selfed plants i n each synthetic was evaluated for endosperm modification each cycle, and seed from 40 plants with the highest endosperm modification were i ntermated to produce the next cycle of selection. Progeny representing each of the five cycles of each synthetic were evaluated for 2 yr (19 91-1992) in replicated held experiments at Urbane, IL. A split plot ex periment, using a randomized complete block design, with synthetics as main plots and cycles as sub-plots, was used to evaluate selection re sponse. Traits evaluated were endosperm modification, grain yield and moisture, 100-kernel-weight, plant height, oil, protein, starch, lysin e content, and lysine/protein ratio. Five cycles of selection showed a significant increase in endosperm modification, Disease Oil Opaque-2 showing a 42% increase and Elite Single Cross Opaque-2 a 31% increase. Significant cycle effects were observed for protein and starch conten t. Significant years x cycles and years x synthetics x cycles interact ions were observed for several traits but were all of the non-crossove r type. No changes in the nutritional characteristics of both syntheti cs were observed as a result of selection for increased endosperm modi fication. The results were obtained without monitoring lysine or trypt ophan during selection. Results indicate Corn Belt adapted opaque-2 sy nthetics with a high degree of endosperm modification can be developed with appropriate selection procedures.