Selection And Evaluation On Maize (Zea Mays L.) Shade-tolerance Indexes

Using 24 maize hybrids and 17 maize inbreds as tested materials, shading treatment was conducted during jointing stage and silking stage, a field experiment was carried out to evaluate the changes of morphological, physiological and yield traits of all genotype maize, then selection and evaluation on maize shade-tolerance indexes were made on the basis of this. The main results were as follows:1. Corn growth and development and organ formation was significantly affected by shading, and there was a significant difference caused by shading among different varieties. Leaf appearance rate slowed, leaves thinned and the functional period of leaves prolonged after shading. When shading treatment was ended, however, the functional period of leaves shortened, leaf area index (LAI) of large Laba stage, silking stage and maturity stage decreased, plant height decreased, the difference control and shading treatment was up to significance except Chang 7-2 (P<0.05), plant stem diameter and dry matter accumulation decreased significantly, anthesis to silking interval (ASI) prolonged.2. Corn photosynthetic characteristics were significantly affected by shading. Net photosynthetic rate (Pn) of maize ear leaf decreased after shading, the difference of control and shading treatment was up to significance except 02500 and Huangzao 4. There was significant difference of changes of chlorophyII a content among varieties, chlorophyII a content of some varieties increased, but others decreased, while chlorophyII b and total chlorophyII content in most genotypes were increased on the shade treatment shich resulted in a reduction of chlorophyII a/b, and also the leaf carotenoid content of most genotypes.3. Maize yield and yield traits were significantly affected by shading. Maize yield decreased significantly by shading, yield of maize hybrid decreased by 24.36%～55.75%, yield of maize inbred decreased by 21.45%～50.04%. Corn ear shortened and became thin, ear axis diameter and kernels per row decreased by shading, but there were no significant regular change of barren ear tip, ear rows and weight per 100 kernels of corn ear.4. Corn grain quality was affected by shading. Starch accumulation of 24 maize hybrids decreased by 25.39%～57.99% after shading, compared with those in control, oil accumulation decreased by 13.41%～53.34%,protein accumulation decreased by 12.77%～54.61%,lysine accumulation decreased by 20.59%～51.82%. Starch accumulation of 17 maize inbreds decreased by 20.90%～51.07% after shading, compared with those in control, oil accumulation decreased by 27.67%～52.76%,protein accumulation decreased by 17.33%～54.33%,lysine accumulation decreased by 16.84%～51.60%. But shading changed component proportion in the grains, starch and oil relative content in the grains of most materials had decreased tendency, but protein and lysine relative content in the grains of most materials had increased tendency.5. Hybrids and inbreds changes of traits according to shading and correlation analysis of changes of traits, ASI, Pn, specific leaf weight (SLW), kernels per row combined with dry matter accumulation of the aboveground parts and yield were suggested to be used as main indexes to evaluate maize hybrid shade tolerance, carotenoid content, plant height, stem diameter,ear length, ear diameter and axis diameter can be used as assistant indexes, Pn, SLW, ear length combined with dry matter accumulation of the aboveground parts and yield were suggested to be used as main indexes to evaluate maize inbred shade tolerance, ASI, plant height, stem diameter, ear diameter, kernels per row and axis diameter can be used as assistant indexes. Cluster analysis considering comprehensive shade-tolerance characters indicated that 14 cultivars (Zhengdan 958, Xundan 20 and Denghai 602, etc.) were of shade-tolerance type and 10 cultivars (Anyu 12 and Yuyu 22, etc.) were of shade-sensitive type. 8 maize inbreds (Qi 319, Zheng 58, Zhong 72, etc.) were of shade-tolerance type and 9 maize inbreds (Huangzao 4, 73-1, Zheng 22, etc.) were of shade-sensitive type.