Formation And Regulation Of Yield And Quality In Two Stains Of Coix (Coix Lachryrma-jobi L.)

Coix (Coix lachryrma-jobi L.), an erect annual or perennial herb of Gramineae, is used as Chinese traditional folk medicine for treatment of edema, dysuria, diarrhea of spleen deficiency, lung carbuncle, periappendicular abscess and verruca plana. It has been contained in Chinese Pharmacopoeia since 2000. The pharmacological activities of anti-tumor, immunoregulation, hypoglycemic, blood pressure decreasing and anti-virus have been reported in rensent years. In addition, coix was titled as "King of the world Gramineas" since the high nutrition values.The resources of coix in China are rich, but the problem of low yield, laid plant, late mature period and the poor ability of desease and insect resistance constrainted the development of coix production. For further selection of good variety to facilitate the future promotion provide useful information of genetic breeding of coix, the main factors affecting the yield and quality information of the two stains of coix which breed and selected from space mutation were researched in this study. The results were as follows:1. Morphology, isozyme and cytogenetis studyThe differences of 2 coix stains in plant morphology were presented on the color of young leaves, stem and stigma. The colors of these parts of Xiehe CoixⅠwere purple, while the Xiehe CoixⅡwere green.In the analysis of isozyme pattens of 2 coix stains, it was found that the SOD and POD isozymes of these 2 stains were basically the same, which indicated a close genetic relationship between them. The POD isozymes of Xiehe Coix I had a lager number and stronger activity, as compared with Xiehe CoixⅡ, which indicate that there were some genetic differences between these 2 stains, and they may belong to the different physical types of the same species.The karyotype formula of the 2 coix stains was 2n= 20= 16m+4sm and the karyotype symmetry was 1A-type. The absolute length of chromosomes of Xiehe CoixⅠand Xie CoixⅡwere 3.01-5.36μm and 2.25-7.99μm, respectively, while the chromosome length ratios were 1.78 and 3.55, respectively. The differences in chromosome morphology of these 2 stains indicated that space mutation had caused different degrees of variation.2. Evaluation the main qualities of coixThe contents of triolein in Xiehe CoixⅠ(1.17%) and Xiehe CoixⅡ(0.97%) were higher than the requirement of "The People's Republic of China Pharmacopoeia 2005 edition (1)". The delay of planting date caused the increasing of triolein content of coicis. The application of potassium and phosphate fertilizers can raised the content of triolein in Xiehe CoixⅠ(70.0%) and Xiehe CoixⅡ(78.2%) significantly, while the application of nitrogen fertilizer had no effect on triolein content.The contents of protein of Xiehe CoixⅠand Xiehe CoixⅡwere 16.7% and 16.5%, respectively, whihe the contents of fat were 5.6% and 6.6%, respectively. The contents of Glu and Leu of the 2 coix were quite high, while Trp and Lys were low. According to ASS, Trp was the first limiting amino acid, and the second limiting amino acid was Lys. The EAA/TAA of Xiehe CoixⅠand Xie CoixⅡwas 37.2% and 37.6%, respectively, while the EAA/NEAA was 0.59 and 0.60, respectively, and the EAAI was 47.71 and 48.55, respectively. The content of oleic acid, linoleic acid and palmitic acid of Xiehe CoixⅠwas 32.2,20.5 and 6.8 mg/g, respectively, which was higher than that of Xiehe CoixⅡ.3. Yield components and the regulation of endogenous hormonesCorrelation analysis and path analysis of yield components showed that aboveground biomass, panicles per plant, number of tillers per plant were the most relevant components of coix. Principal component analysis showed that the spike number per plant, biomass, number of tills of Xiehe CoixⅠwere high, while the grains per panicle and kernel weight were medium. As to Xiehe CoixⅡ, the spike number per plant, biomass, number of tills and grains per panicle were lower, as compared with I. Thus Xiehe CoixⅠwas more productive.The level of endogenous hormone IAA/ZR of different coix stains was significantly different. Throughout the tiller development process, IAA/ZR ratio of Xiehe CoixⅠwas always higher than CoixⅡ. The difference was most significantly at the beginning and ending period of tiller development. Thus there was a close relationship between the endogenous hormone and the development of tillers.4. Study on photosynthetic and chlorophyll fluorescence characteristics of coixStudy on photosynthetic showed that, at seedling and growth stage, the content of chlorophyll a of Xiehe CoixⅠwas lower than that ofⅡ, but the content of carotenoids was higher thanⅡ. The ratio of a/b of I was decreased by increasing the content of chlorophyll b, thus the light captured by leaves was increased. At maturity stage, the content of chlorophyll a of I was increased significantly.The diurnal change of net photosynthetic rate (Pn) of coix showed a single peak curve. In the morning, the Pn increased significantly with the increase of photosynthetic active radiation, and CoixⅠincreased faster thanⅡ. The Pn reached the maximum at 12:00 (Coix I:18.2μmol CO2 m-2s-1; CoixⅡ:18.9μmol CO2 m-2s-1), then deceased gradually and reached the lowest at sunset. Responses of net photosynthetic rate to light for coix showed that the light compensation point (LCP) of CoixⅠ(24.0μmol m-2s-1) was lower and the light saturation point (LSP) (1197μmol m-2s-1) was higher, thus the using range of light intensity was wider, when compared with CoixⅡ(LCP:50.0μmol m-2s-1, LSP:931μmol m-2s-1).The Fo, Fv/Fm,ΦPSII and qP of CoixⅠwere higher thanⅡ, which means that the PSII reaction center of Coix I's leaves were more active, with higher electron transport activity and light energy conversion efficiency, as compared with CoixⅠ. However, the NPQ of CoixⅡwas higher thanⅠ, indicated that the potential heat dissipation capacity of PSII was strong, and can effectively prevent the damage on the photosynthetic apparatuscaused by excess light.5. Determination of antioxidant enzyme activitiesAt seedling stage, the activities of SOD and APX of CoixⅡwere significantly higher thanⅠ, but the activities of POD, CAT, GR, anthocyanins and flavonoids were significantly lower. At growth stage, the activities of SOD, POD and APX of CoixⅡwere significantly higher thanⅠ, but the activities of CAT, anthocyanins and flavonoids were significantly lower thanⅠ. At flowering stage, the activities of SOD, POD and APX of CoixⅡwere significantly higher than I, but the activities of GR, anthocyanins and flavonoids were significantly lower thanⅠ. From these results, we concluded that CoixⅠresist free radicals mainly through the antioxidant enzymes, while CoixⅠmainly through anthocyanins and flavonoids.6. Fertizilation, planting density and planting dateThe differences of yield and its components of coix treated with different fertizilations levels and combinations were significant. The yield of CoixⅠtreated with N1P2K2 was the highest (284.4 kg/667m2), the conresponding output value was 2491 yuan/667m2. The equations between yield and dosage of single-fertizilation application were established. The economic optimal dosage of N, P and K applied on CoixⅠwas 6.64, 5.38, and 6.63 kg/667m2. Since the increase of yield of CoixⅠwas mainly through the increase of grain number and seed setting rate, and P and K were the important fertizilation to increase the yield of CoixⅠ, the results of fertizilation uptake analysis indicated that the aborption of P and K of CoixⅠcould be inhanced by reducing the application of N.Effects of different planting densities and planting date on yield and its components in coix were studies using two-factor randomized block design. The results showed that the difference of yield and its components affected by plant densities and planting dates were both significantly. The optimal planting density was 60cm×80cm spacing-row, with respects to increasing economic benefits of coix. While the planting date delayed 20 days, the yield of Xiehe CoixⅠwas 8.2% decreased, and was mainly affected by the number of tillers. Considering the increased consumption of human and irrigation, and the decrease of the content of triolein when planting early, the optimal planting date in Beijing was around mid-May.