The Differences Of Yield Formation And Physiological Basis Of Different Genotypes Of Bt Cotton Varieties

The experiment was conducted in the scientific farm of Shandong Agricultural University from 2013 to 2014. Three genotypes of Bt cotton varieties: Jimian 169(J169),Lumianyan No.21(L21) and Daizimian 99B(99B) were used under field condition. The growth and development traits, physiological characteristics of cotton leaves, development and spatio-temporal distribution of cotton bolls were studied to illustrate the differences of yield formation and physiological basis of different genotypes of Bt cotton varieties. The main results were listed as follows:(1) J169 compared with L21 and 99 B, plant height, first fruiting branch height, fruit first node and fruit node numbers of per plant were significantly lower, while there was no changes of the fruiting branch numbers. There were no significant differences between L21 and 99 B,besides the drop of fruiting nodes of L21.(2) J169 compared with L21 and 99 B, there were greatly increased in the chlorophyll content, photosynthetic rate and actual photochemical efficiency, respectively, which improved the photosynthetic capacity of cotton leaves consequtly; SOD and CAT activity of cotton leaves were increased, POD activity and MDA content of cotton leaves were reduced,which decreased peroxide production and accumulation, as well as the reduction of injury to cell envelop caused by active oxygen. L21 compared with 99 B, the chlorophyll content,photosynthetic rate and actual photochemical efficiency of main stem functional leaves were significantly improved at the beginning of the growing season, respectively, but the chlorophyll content, photosynthetic rate and actual photochemical efficiency of L21 leaves droped rapidly during the latter stages of the growing season; SOD and CAT activity of cotton leaves were lower, POD activity and MDA content of cotton leaves were increased rapidly,which accelerated the senescence of leaves. There were the lowest chlorophyll content,photosynthetic rate and actual photochemical efficiency of 99 B cotton leaves during the whole growth period, which illustrated the lower photosynthetic capacity.(3) The starting and ending time in rapid growth period of boll dry matter weight, fiber weight and seed weight of J169 were significantly delayed to L21 and 99 B, while its duration was long, the average growth rate was increased significantly, and mature boll dry matter weight, fiber weight and seed weight were greatly increased. L21 compared with 99 B, the starting and ending time in rapid growth period of boll dry matter weight, fiber weight and seed weight were significantly earlier, but its duration and average growth rate were no changes, the mature dry matter weight was increased. There were the earlest starting and ending time in the speedy rising period of 99 B, the duration and average growth rate were the lowest, and mature dry matter weight of every part of cotton boll were also lowest during the whole boll developing stage. There existed no greatly differences of dry matter distribution of each part of cotton boll in spite of the significantly different of its dry matter weight among three genotypes of Bt cotton varieties.(4) There were greatly increased of soluble sugar content, total nitrogen content and C/N ratio in subtending leaf of J169 than L21 and 99 B. The soluble sugar content and total nitrogen content in subtending leaf of L21 were higher than 99 B, but the C/N ratio was no obvious changes. There were the lowest soluble sugar content, total nitrogen content and C/N ratio in subtending leaf of 99 B. The relationship between soluble sugar content and every part of cotton boll dry matter accumulation and distribution were significantly positive correlation among three different genotypes of Bt cotton varieties. There were greatly negative correlation between nitrogen content and every part of cotton boll dry matter accumulation and distribution, besides the boll-shell weight, boll-shell ratio and seed ratio of L21 and the seed ratio of J169. The relationship between C/N ratio and every part of cotton boll dry matter weight were greatly positive correlation, besides the boll-shell weight of L21; there was significantly positive correlation between C/N ratio and boll-shell ratio, and significantly negative correlation between C/N ratio and seed ratio and fiber ratio among three different genotypes of Bt cotton varieties.(5) There was lower bolls retained intesity in circle nodes of J169 than L21, and higher than 99B; the bolls retained intesity in periphery nodes were greatly decreased than L21 and99B; but the boll weight, lint percentage and micronaire were significantly increased; the fiber length, strength, elongation and uniformity were declined. The bolls retained intesity weregreatly increased in circle nodes and declined in periphery nodes of L21 than 99B; the boll weight, lint percentage and micronaire were significantly increased, as well as the fiber length,strength, elongation and uniformity. There were the highest bolls retained intesity in circle nodes and periphery nodes of 99B; but its boll weight, lint percentage and micronaire were lower; the fiber length, strength, elongation and uniformity were higher.(6) J169 compared with L21 and 99 B, the seed cotton yield and lint cotton yield increased significantly which was attributed to the increased boll weight; in spite of bolls per plant were lower. L21 compared with 99 B, the seed cotton yield and lint cotton yield were greatly enhanced, and its boll weight was also increased, but the bolls per plant and lint percentage were no significant difference. Limited by the minimal boll weight, the seed cotton yield and lint cotton yield of 99 B were the lowest.