Development of a drought stress-resistant rice restorer line through Oryza sativa–rufipogon hybridization

Restorer line F6 (Oryza sativa L. ssp. indica) has been widely used in hybrid rice breeding systems in southern China. However, line F6 is susceptible to drought stress, which restricts its utilization in many areas. Dongxiang wild rice (DXWR, Oryza rufipogon Griff.) has strong drought stress resistance, but the molecular factors responsible for drought resistance in DXWR remain unknown. In this study, we used the combination of phenotypic selection and molecular marker-assisted selection (MAS) to improve the drought stress resistance of line F6 by introgression of qSDT12-2, a large effect drought stress-related quantitative trait locus identified in DXWR. Molecular MAS was carried out using linked marker RM1226, which is associated with qSDT12-2. Genomic background assessmentwas performed using 112 polymorphic markers. Finally, a stable drought stress-resistant backcross inbred line (BIL) was developed from a BC5F5 population, termed BIL627. Genetic constitution analysis revealed that the genome of BIL627 is almost identical (99.1%) to that of the restorer line F6. Further, BIL627 showed no yield penalty and no decrease in restorationability under normal conditions. Taken together, our findings reveal the intrinsic value of using genetic resources present in wild species of Oryza to improve undesirable traits found in cultivated rice.

Transcriptome analysis of phosphorus stress responsiveness in the seedlings of Dongxiang wild rice (Oryza rufipogon Griff.)

Abstract Background: Low phosphorus availability is a major factor restricting rice growth. Dongxiang wild rice (Oryza rufipogon Griff.) has many useful genes lacking in cultivated rice, including stress resistance to phosphorus deficiency, cold, salt and drought, which is considered to be a precious germplasm resource for rice breeding. However, the molecular mechanism of regulation of phosphorus deficiency tolerance is not clear. Results: In this study, cDNA libraries were constructed from the leaf and root tissues of phosphorus stressed and untreated Dongxiang wild rice seedlings, and transcriptome sequencing was performed with the goal of elucidating the molecular mechanisms involved in phosphorus stress response. The results indicated that 1184 transcripts were differentially expressed in the leaves (323 up-regulated and 861 down-regulated) and 986 transcripts were differentially expressed in the roots (756 up-regulated and 230 down-regulated). 43 genes were up-regulated both in leaves and roots, 38 genes were up-regulated in roots but down-regulated in leaves, and only 2 genes were down-regulated in roots but up-regulated in leaves. Among these differentially expressed genes, the detection of many transcription factors and functional genes demonstrated that multiple regulatory pathways were involved in phosphorus deficiency tolerance. Meanwhile, the differentially expressed genes were also annotated with gene ontology terms and key pathways via functional classification and Kyoto Encyclopedia of Gene and Genomes pathway mapping, respectively. A set of the most important candidate genes was then identified by combining the differentially expressed genes found in the present study with previously identified phosphorus deficiency tolerance quantitative trait loci. Conclusion: The present work provides abundant genomic information for functional dissection of the phosphorus deficiency resistance of Dongxiang wild rice, which will be help to understand the biological regulatory mechanisms of phosphorus deficiency tolerance in Dongxiang wild rice.

Identification and quantification of anthocyanin pigments in colored rice

Anthocyanin pigments from varieties of black, red and wild rice were identified and quantified to evaluate their potential as nutritional function, natural colorants or functional food ingredients. Anthocyanin extraction was conducted with acidified methanol with 0.1M HCl (85:15, v/v) and identification of anthocyanin, aglycone and sugar moieties was conducted by comparison with purified standards by HPLC, Ultraviolet-Visible absorption spectrophotometer and paper chromatography. Black and wild rice showed three different types of pigments by HPLC whereas red rice variety did not show any anthocyanins. Out of three pigments detected, one (peak 2) was characterized as cyanidin-3-glucoside (C3G) by comparison of spectroscopic and chromatographic properties with an authentic standard, and another (peak 3) was tentatively identified as cyanidin-fructoside on the basis of spectroscopic properties with lambdamax of aglycone in 1% HCl methanol at 537 nm, electrospray ionization mass spectra with major ions at 449 and 287 m/z and chromatographic properties. But another pigment (peak 1) has not been characterized. The most abundant anthocyanin in black and wild rice was C3G.

Ultrastructure of the wild rice Oryza grandiglumis (Gramineae) in Costa Rica

Oryza grandiglumis is a wild species of rice endemic to tropical America. This species was first found in 1998 in the wetlands of Caño Negro, located in the northern part of Costa Rica. Twenty five plants of O. grandiglumis were processed for scanning electron microscope. An ultrastructural description of the leaf blade, ligule, auricles, spikelet and caryopsis, with an emphasis on structures of taxonomic value. The leaf blade has a characteristic cuticular wax pattern, composed of dense rod-like structures, and is surrounded by papillae, zipper-like silica cells, abundant bulky prickle trichomes, and hooked trichomes. The blade's edge has three rows of hooked prickle trichomes of various sizes. The auricles wrapped the culm, with long attenuated trichomes at the edges; the base was surrounded by oblong cells. The ligule is a blunt membrane covered by short prickle trichomes. Spikelet morphology is characteristic of the Poaceae family, but the sterile lemmas were nearly as long as the fertile lemmas, and they have an unique crown-like structure of lignified spines between the rachilla and the fertile lemmas. Comparison with Brazilian specimens of O. grandiglumis revealed little differences in the ultrastructural characteristics.

El arroz silvestre Oryza grandiglumis es endémico de América. Se localiza en la zona norte de Costa Rica, principalmente en el humedal de Caño Negro y del Río Medio Queso. Es una planta vigorosa y grande. Su nombre deriva del gran tamaño de las lemas estériles (glumas). Presentamos una descripción ultraestructural de la lámina foliar, lígula, aurículas, espiguilla y cariópside, con énfasis en las estructuras de valor taxonómico, usando el microscopio electrónico de barrido. La lámina foliar se caracteriza por presentar un patrón de cera cuticular en forma de densos bastoncillos. Presenta estomas rodeados de papilas, células de sílice en forma crenada, varias formas de papilas de cera, distribuidas en forma muy regular, y tricomas espinosos abultados en la base y tricomas ganchudos. En el borde de la lámina hay tres hileras de tricomas espinosos ganchudos de diferente tamaño. Las aurículas son envolventes y los bordes presentan tricomas atenuados largos cubiertos en la base por células alargadas. La lígula es truncada y cubierta de tricomas espinosos pequeños. La morfología de la espiguilla es algo similar a las de las otras especies de la familia Poaceae, pero las lemas estériles son casi del mismo tamaño que las fértiles. Además se observó entre la raquilla y las lemas fértiles una corona de espinas lignificadas. Ultraestructuralmente, esta población es similar a las brasileñas.

EFFECT OF CHINESE WILD RICE ON LIPID METABOLISM AND INFLAMMATORY FACTORS IN RATS FED WITH HIGH CHOLESTEROL DIETS / 营养学报

Objective To study the effect of Chinese wild rice diet on lipid metabolism in rats. Method Forty four male SD rats were divided into 4 groups:control group, high lipid group, white rice-flour group and Chinese wild rice group. All groups were given different experimental diets for 8 w and body weights, serum TC, TG, HDL-C, high sensitive C-reactive protein (hs-CRP), TNF-? and IL-6 were measured. Results The hyperlipidemic rat model was successfully induced. When compared with high lipid group and white rice-flour diet group, serum TG and TC contents were significantly decreased, and HDL-C significantly increased in the Chinese wild rice group. Moreover, Chinese wild rice group had lower contents of serum hs-CRP and TNF-? than those in high lipid group and white rice-flour group, but no effect on serum IL-6. Conclusion Chinese wild rice could improve lipid metabolism and low-grade inflammation of hyperlipidemic rats induced by high lipid diet.