| In recent years, maize and soybean relay strip intercropping system development in Southwest rapidly. It made full use of the boundary line of advantage, implement maize and soybean harmonious coexistence, one season double charge, increased soybean production. However, due to the effect of maize shading, making the change of soybean seedling growth microenvironment under the relay intercropping system, especially the light environment (light intensity and light quality), the photosynthetic efficiency and morphogenesis of soybean were influenced, soybean appeared the obvious response, that was, stem slender, delicate and easy to lodging, which influenced the soybean harvest.Therefore, shade-tolerant and resistance lodging of Nandou12 and non-shade tolerant and non-resistance lodging of NanO32-4 were taken as experimental materials for this research during 2013 and 2014 year. From the molecular level, studying on the expression of genes, coded key enzymes of the endogenous gibberellins metabolism pathways. Explained the reason of the difference of shade avoidance response between different shade-tolerant and resistance lodging soybean varieties under the relay intercropping system. To provide the theoretical basis for weakening the shade avoidance response of soybean, screening shade-tolerance soybean materials. The results of the study were as follows.1. Under maize-soybean relay strip intercropping system and soybean sole cropping system, two soybean materials were studied. The results showed that:under the relay intercropping system, due to the effect of maize shading at the seeding stage, Nandoul2 and NanO32-4 all appeared the obvious response, that was, the node number reducing, plant height and internodes length increasing significantly, as the varieties had different degree, the vine and lodging at seeding stage showed the significant difference. NanO32-4 was significantly influenced, and the rate of vine and lodging, was also higher than that of Nandoul2. Under relay intercropping, two soybean varieties lodging rate difference was not significant at V2, and lodging rate extremely significant difference at V6. In conclusion, the special light environment on the influence of different genotype varieties was different under relay intercropping. The phenotype of the soybean plant could be used as an important evaluation indicator of soybean resistance.2. Studying on the microscopical structure of internode of main stem of two soybean varieties reveal that cell length of stem pith, xylem and phloem increasing remarkably, but cambium cells no obvious change. The number of various organizations cells decreases and the length of them of NanO32-4 longer than these of Nandoul2. It revealed that the increasing of these two plant height was from cell elongation, not cell division.3. Gas chromatography-mass spectrometry analyses measures the level of gibberellins, such as GA53, GA20, GA1, GA4, GA8 and GA34. The results showed that the content of GA53, GA1 and GA4 in endogenous gibberellins metabolic pathways of different soybean stem were difference at different growth stages. The gibberellins content of Nandou12 were low and the same as in NanO32-4 are contrary at V2 stage under sole cropping. GA4 content of Nandoul2 was decreased obviously than NanO32-4. At V6 stage, content of GA1 and GA53 were not significant difference between the two varieties, but the difference of GA4 was obvious. The content of gibberellins appeared difference between varieties at V2, phase difference was obvious at V6. The greater difference of the GA4 content, the stem elongation rate was greater also. Fail to detect GA20 and GA8 and GA34 of soybean stem.4. The real-time qPCR with SYBR(?) Green â…¡ analyses measures the expression of the genes encoding the key enzymes of the gibberellins metabolic pathway. The result showed that GmGA20ox2 and GmGA3oxl genes caused higher plants, the content of gibberellins in the stem increased. At the same time, content of activity gibberellins positive and negative feedback genes encoding key enzyme in gibberellins metabolic pathways. Such as the excessive expression of GmGA20oxl, GmGA3ox6, GmGA2oxl, GmGA2ox2, GmGA2ox6 and GmGA2ox7 caused dwarf plant, when content of activity gibberellins high. All of the expression GA20-oxidase, GA3-oxidase, and GA2-oxidase genes of stalk of NanO32-4 were higher than Nandoul2, except one GA deactivating of GmGA2ox4, leading to remain high GA4 content in the stem tip of NanO32-4, thus showed stronger shade-avoidance reaction.5. The laboratory experiment simulation filed environment. The test results showed that contrasted with gibberellins treatment plants, after the application of Uniconazole, the plants were stocky under green film. The expression of gibberellins synthetic genes down-regulated, or gibberellins deactivating gene up- regulated, except GmGA2ox4. The test results of laboratory experiment and field test were consistent. The genes transcription level of key enzymes in gibberellins metabolism pathway of stem regulate plant height. In comparison with the published corresponding sequences, similarities of the nucleotide and putative amino acid sequences of the cloned GmGA20ox1 gene were 100%. The gene regulation of plant in different varieties was not influenced by environmental factors.6. The results of cloning the gene encoding the key enzymes in the gibberellins metabolic pathway sequencing showed that the GmGA3ox6 and GmGA20ox2, the gene cloning gibberellins synthetic, have single different loci of different soybean varieties, there was the closed relationship with the regulation of plant high.In conclusion, under maize-soybean relay strip intercropping system, endogenous GA of soybean stem for excessive elongation was mainly regulated by GA4. Synthesis of soybean endogenous GA4 was effective by the genotypes and the light environment, influencing the growth and development of soybean stem, which finally results in the typical differences of shade lodging phenotype between varieties. |
PDF Full Text Request