Quality characteristics and field performance of selectable marker-free transgenic rice with antisense Wx gene and improved quality derived from the elite parents of hybrid indica rice

In rice grains, high amylose content (AC) is correlated with poor grain quality, particularly in indica hybrid rice. To obtain indica hybrid rice with improved cooking and eating qualities, we introduced the antisense Waxy (Wx) gene into 2 elite parental lines of indica hybrid rice by using co-transformation methods. Subsequently, we selected several elite homozygous transgenic lines that did not contain the selectable marker. The expression of the endogenous Wx gene of the selected transgenic lines was significantly downregulated, resulting in low AC in the mature seeds; moreover, the AC in some lines reduced to the level observed in glutinous rice. With the decrease in AC, the gel consistency of the transgenic rice became softer, and the gelatinization temperature tended to be higher than those of the wild types, especially in the case of the Longtefu-derived transformants. We also analyzed the pasting properties of the selected transgenic low-AC lines, and we noted an improvement in the pasting properties of the transgenic rice lines. The results from a field trial indicated that the grain weights of the transgenic lines with lower AC exhibit remarkable reduction compared with those of the wild types.     

Improvement of bacterial blight resistance of hybrid rice in China using the Xa23 gene derived from wild rice (Oryza rufipogon)

A novel bacterial blight (BB) resistance gene, Xa23, identified from Oryza rufipogon was introgressed into three popular restorer lines (Minghui63, YR293 and Y1671) for wild abortive cytoplasmic male sterility by marker-assisted backcross breeding approach in combination with artificial inoculation and stringent phenotypic selections. The three derived BB resistant restorer lines (Minghui63-Xa23, YR293-Xa23 and Y1671-Xa23) and their hybrid combinations with Zhenshan97A (Shanyou63-Xa23), NongfengA (Fengyou293-Xa23) and Zhong9A (Zhongyou1671-Xa23) demonstrated similar BB resistance spectrum as the donor parent, CBB23 (B). The newly developed BB resistant restorers and their derived hybrids were identical to their respective original versions for agronomic traits especially under disease free condition. However, under severe disease condition, the three BB resistant restorer lines exhibited significantly higher grain weight and spikelet fertility as compared to the respective original restorer lines thus further resulting in BB resistant hybrids with significantly higher grain yields than their respective popular original hybrids. The results indicated that the Xa23 gene could completely express its dominant broad spectrum resistance in different backgrounds of both restorer and male sterile lines across different growth stages, suggesting its immense breeding value in BB resistance improvement for hybrid rice. Moreover, a reasonable utilization and deployment of Xa23 gene for efficient control of BB disease in hybrid rice production was recommended.     

Influence of transgenic hybrid rice expressing a fused gene derived from cry1Ab and cry1Ac on primary insect pests and rice yield

Although dozens of transgenic Bacillus thuringiensis (Bt) rice lines have been developed, none of them has been released to farmers. Under field conditions, we evaluated the influence of a hybrid Bt rice on the primary rice insect pests and rice yield in 2005 and 2006. Four treatments were evaluated, including Bt and non-Bt rice treated with insecticides when necessary, and unprotected Bt and non-Bt rice. Unprotected Bt rice exhibited stable and high control of the three primary lepidopteran pests, Chilo suppressalis Walker, Tryporyza incertulas Walker and Cnaphalocrocis edinalis Güenée. Under unprotected conditions, larval densities of these three pests in Bt plots decreased by 87.5–100% compared to those in non-Bt plots, and percentages of damaged stems and leaves remained less than 0.6% during the entire rice growing season. In early rice growth stages, populations of two important planthoppers, Nilaparvata lugens Stål and Sogatella furcifera Hovarth, were significantly affected only by protection level (protected vs unprotected). However, in late rice growth stages (filling and maturing), densities of planthoppers were significantly affected both by protection level and by rice type (Bt vs non-Bt), and densities of N. lugens were significantly higher in Bt plots than in non-Bt plots under unprotected conditions. Pesticide sprays were reduced by 60 and 50% in protected Bt vs protected non-Bt plots in 2005 and 2006, respectively. Yield of unprotected Bt rice increased by 60–65% compared to unprotected non-Bt rice, but decreased by 28–36% compared to protected Bt rice. These results show that Bt rice increased yield greatly, but still required pesticide sprays to avoid losses caused by non-target insect pests.     

Molecular marker assisted selection for improvement of the eating,cooking and sensory quality of rice (Oryza sativa L.)

II-32B is a key maintainer line used for hybrid rice breeding in China. However, it is of poor quality for most Chinese consumers because of its high apparent amylose content (AAC), high gelatinization temperature (GT) and non-fragrance. It is well known that the AAC, GT and fragrance traits are largely controlled by the Wx, starch synthase IIa (SSIIa), and fragrance (fgr) genes, respectively. With the aid of functional markers, we improved the quality of II-32B by introgressing the Wx, SSIIa, and fgr genes from Yixiang B, a fragrant maintainer line that has low AAC and low GT. The microsatellite allele (CT)₁₇ of Wx, the contiguous single nucleotide polymorphism TT allele of SSIIa and the 8-bp deletion allele of fgr were transferred to II-32B by two backcrosses and three selfings. Molecular marker assisted selection was applied in the series to select for individuals carrying Wx-(CT)₁₇, SSIIa-TT, and fgr-deletion alleles. According to the marker genotypes, seventeen homozygous lines for Wx-(CT)₁₇, SSIIa-TT, and fgr gene markers were finally selected. The improved II-32B lines were fragrant with reduced AAC and GT.     

Identification of novel glutelin subunits and a comparison of glutelin composition between japonica and indica rice (Oryza sativa L.)

Glutelin, a major protein in rice grains, is encoded by a multigene family. However, its protein composition is not well characterised. Here, we identified and characterised two novel glutelin subunits, GluBX and GluC. The individual glutelin subunits of japonica cv. Nipponbare and indica cv. 93-11 rice were analysed using 2-dimensional gel electrophoresis, LC–MS/MS, and Western blotting. Comparison of the glutelin profiles between three japonica and three indica cultivars indicated two distinct subunits (GluA-1 and GluA-3 isomers) and a distinction in the subunit composition (notably GluA-3 and Lys-rich GluB-1 components) of these two subspecies. Sequence alignment revealed different nutritional (Lys residues) and functional (Cys residues) characteristics between the type-A and type-B glutelin subfamilies. We also analysed amino acid and total protein contents of the grains in thirty-five cultivars, and we demonstrated that the Lys-rich glutelin composition of indica cultivars is superior to that of japonica cultivars. The Lys-rich and Cys-poor GluBX subunit is a native protein and is a high nutritional protein in grains. Our combined approaches for the identification of glutelin subunits have revealed the nutritional characteristics of individual subunits in rice, and this knowledge will provide new insights for improving grain quality during rice breeding.     

Physiological characterization of introgression lines derived from an indica rice cultivar, IR64, adapted to drought and water-saving irrigation

Water scarcity threatens sustainable rice production in many irrigated areas around the world. To cope with the scarcity, aerobic rice culture has been proposed as a promising water-saving technology. The objective was to elucidate the physiological attributes behind the performance of rice introgression lines in water-saving culture. We evaluated yield potential and physiological adaptation traits to water deficit of BC₃-derived lines with the genetic background of an elite indica cultivar, IR64, in the field and in pot experiments. One line, YTH183, had 26% higher yield than IR64 under non-stress conditions (895 vs. 712 g m⁻² on average). This was attributed to enlarged sink capacity due to large grain size, which contributed to more efficient use of assimilates and hence a higher harvest index. YTH183 also showed better dehydration avoidance under intermittent soil drying, due to the adaptive response of deep rooting to water deficiency. The grain yield of YTH183 exceeded that of IR64 by 92-102% under moderate water deficit caused by limited irrigation in aerobic rice culture (143 vs. 72 g m⁻²). Two introgressed segments on chromosomes 5 and 6 might, at least in part, confer the higher yield potential and greater dehydration avoidance in YTH183 simultaneously. Advanced backcross breeding combined with molecular genetics and physiological characterization of introgressed segments would be effective for developing new rice cultivars with high yield potential and drought adaptation traits.     

Development of an Aegilops longissima substitution line with improved bread-making quality

This study focuses on the effect of Aegilops longissima on wheat bread making quality. Chromosome 1S^l disomic addition line of Ae. longissima (DAL1S^l) had significantly higher dough strength, grain hardness, mixographic peak height, band width, and unextractable polymeric protein content compared with wheat. DAL1S^l also had additional glutenin and gliadin proteins contributed by Ae. longissima. The larger size of 1S^l coded HMW-GSs sequenced from DAL1S^l and their phylogenetic similarity to the D-genome-coded subunits were suspected to be one of the major reasons for the increased dough strength of DAL1S^l. To transfer the chromosome 1S^l genes responsible for the good bread-making quality to wheat, we generated a chromosome-specific disomic substitution line [DSL1S^l(1A)] by crossing DAL1S^l with nulli 1A tetra 1B genetic stock and further selection. Grain quality analysis revealed significantly lower grain hardness and significantly higher dough strength, farinograph development time, stability time, gluten index, bread loaf volume, and bread quality score in DSL1S^l(1A), compared with wheat. However, the increased bread loaf volume and quality were not proportional to the relatively higher increases in dough strength and gluten index, indicating importance of other traits influencing bread making quality. The presence of a minor hardness locus on chromosome 1A is speculated.     

Inheritance of flour paste viscosity is associated with a rice Waxy gene exon 10 SNP marker

Apparent amylose content is a key element for characterizing a rice (Oryza sativa L.) cultivar for cooking quality. However, cultivars with similar apparent amylose content can have widely varying quality attributes, including major parameters of flour paste viscosity. It has been postulated that the presence of a rice Waxy gene single nucleotide polymorphism (SNP) marker is associated with elevated Rapid Visco Analyser (RVA) properties in specific high amylose rice cultivars. A mapping population derived from a cross between two varieties, Cocodrie and Dixiebelle, having similar high apparent amylose contents, but with different paste viscosity properties and Waxy gene markers was analyzed for the genetic segregation of various pasting properties, measured with RVA instrumentation. Marker inheritance analyses revealed that the Waxy exon 10 SNP marker was associated with the proportion of soluble to insoluble apparent amylose and most RVA pasting measurements. Waxy gene markers can be used to efficiently improve the selection of rice with desirable characteristics, particularly for superior parboiling and canning quality.     

Potential of Waxy gene microsatellite and single-nucleotide polymorphisms to develop japonica varieties with desired amylose levels in rice (Oryza sativa L.)

The Waxy (Wx) gene is responsible for the synthesis of amylose, a key determinant of the cooking and processing qualities of rice. Polymorphisms of CT-microsatellite and G–T single-nucleotide polymorphism (SNP) in the Wx gene and their relationship to amylose content (Ac) were explored using 178 non-waxy rice genotypes. Nine Wx microsatellite alleles, namely (CT)10 and 11, and (CT)14–20 were identified and 11 haplotypes were recognised by different combinations of CT-microsatellite and G–T SNP. Amylose content analysed in a random set of 39 genotypes was correlated with different microsatellite alleles/haplotypes. The highest Ac levels (>30%) correlated with (CT)10 and 16, high (26–30%) with (CT)11, 15 and 20, and intermediate (21–25%) with (CT)14, in all cases with G at the G–T SNP. The CT-classes (CT)17 and 18 (mean Ac value of 21%), could be subdivided into low amylose haplotypes (16–20%) for 17T and 18T and intermediate amylose haplotypes (21–25%) for 17G and 18G. The use of haplotypes proved to discriminate between intermediate and low amylose accessions within the same microsatellite class. Analyses of a segregating population of a cross between low and high Ac parents showed that CT-microsatellite may help to classify breeding lines and identify pollen contamination. We suggest that CT-microsatellite together with G–T SNP may be used as molecular marker by breeders to develop varieties with desired amylose levels.     

Agronomic and quality characteristics of triticale (X Triticosecale Wittmack) with HMW glutenin subunits 5+10

Sets of triticale (X Triticosecale Wittmack) lines derived from the cv. Presto with HMW glutenin allele Glu-D1d (subunits 5+10) translocated from bread wheat (Triticum aestivum L.) chromosome 1D to chromosome 1R were evaluated for agronomic and grain quality characteristics in 2002–2005. Two different translocation types were used: (a) single translocation 1R.1D₅₊₁₀-2 where the long arm of 1R carries the wheat segment from 1DL with the Glu-D1d replacing a secalin locus Sec-3, (b) double translocation Valdy where the long arm of 1R has the translocation 1R.1D₅₊₁₀-2 and the short arm has a segment from 1DS carrying wheat loci Gli-D1 and Glu-D3. The presence of Glu-D1d was determined by polyacrylamide gel electrophoresis (PAGE-ISTA) and DNA markers. The tested lines of triticale were compared with the check triticale cv. Presto and with wheat cultivars of different bread making quality (E-C quality classes). Single translocation 1R.1D₅₊₁₀-2 reduced grain yield by 16% and Valdy translocation by 24% as compared with cv. Presto. The Valdy translocation had substantially shortened spike length and reduced specific weight in comparison with check cv. Presto. Wet gluten content (according to the Perten method) was 12% in both translocation types, 8% in check Presto and on average 24% in wheat. Translocations increased the Zeleny sedimentation value (Valdy — 27 ml, 1R.1D₅₊₁₀-2 – 25 ml, cv. Presto — 23 ml). Triticale had a very low Hagberg falling number (FN) of 62–70 s without significant differences, while wheat had on average 301 s. The translocations did not significantly increase loaf volume; however, they improved loaf shape (height/width ratio): Valdy — 0.61, 1R.1D₅₊₁₀-2 – 0.56, cv. Presto 0.44, wheat on average 0.70. The dough was non-sticky in Valdy, slightly sticky in 1R.1D₅₊₁₀-2 and sticky in cv. Presto. Problems with a low FN for improving bread making quality of triticale are discussed. Higher bread making quality can be influenced by appropriate combination with donors of low α-amylase activity.     

Responses of SUB1 rice introgression lines to submergence in the field: Yield and grain quality

Prolonged submergence is a major constraint to rice production, affecting over 15 million ha in South and Southeast Asia and causing an annual yield loss of over US$ 600 million. This is because all the modern high-yielding rice varieties are sensitive to complete submergence. A major quantitative trait locus (QTL), SUB1, associated with submergence tolerance, was mapped on chromosome 9 and recently bred into popular rainfed lowland rice varieties sensitive of complete submergence, using marker-assisted backcrossing (MABC). Here, we assessed the impact of introgressing SUB1 into three rice varieties popular in farmers’ fields of South and Southeast Asia, Swarna, Sambha Mahsuri, and IR64, under control conditions as well as following submergence in the field. Under control conditions, no differences were observed between Sub1 introgression lines and their recurrent parents in grain yield or quality aspects. Submergence substantially delayed flowering and maturity, and reduced grain yield, shoot biomass, harvest index, and yield components across cultivars. The reduction in yield was more drastic in the sensitive varieties, particularly when submerged for longer duration (17 d). The significant decline in grain yield was mainly attributed to reductions in grain filling, number of grains per panicle, and grain weight. The SUB1 QTL is effective in conferring tolerance of submergence for about 12–17 d, depending on floodwater conditions. Sub1 introgression lines showed a yield advantage of up to 3.8 t ha⁻¹ and slightly better grain quality after submergence compared with their parents. Apparently, the introgression of SUB1 into popular varieties did not have any negative impact on their performance under control conditions but considerably enhanced their yield and grain quality following short-term submergence.     

High level of resistance to Sclerotinia sclerotiorum in introgression lines derived from hybridization between wild crucifers and the crop Brassica species B. napus and B. juncea

Sclerotinia rot caused by the fungus Sclerotinia sclerotiorum is one of the most serious and damaging diseases of oilseed rape and there is keen worldwide interest to identify Brassica genotypes with resistance to this pathogen. Complete resistance against this pathogen has not been reported in the field, with only partial resistance being observed in some Brassica genotypes. Introgression lines were developed following hybridization of three wild crucifers (viz. Erucastrum cardaminoides, Diplotaxis tenuisiliqua and E. abyssinicum) with B. napus or B. juncea. Their resistance responses were characterized by using a stem inoculation test. Seed of 54 lines of B. napus and B. juncea obtained from Australia, India and China through an Australian Centre for International Agricultural Research (ACIAR) collaboration programme were used as susceptible check comparisons. Introgression lines derived from E. cardaminoides, D. tenuisiliqua and E. abyssinicum had much higher levels (P < 0.001) of resistance compared with the ACIAR germplasm. Median values of stem lesion length of introgression lines derived from the wild species were 1.2, 1.7 and 2.0 cm, respectively, as compared with the ACIAR germplasm where the median value for stem lesion length was 8.7 cm. This is the first report of high levels of resistance against S. sclerotiorum in introgression lines derived from E. cardaminoides, D. tenuisiliqua and E. abyssinicum. The novel sources of resistance identified in this study are a highly valuable resource that can be used in oilseed Brassica breeding programmes to enhance resistance in future B. napus and B. juncea cultivars against Sclerotinia stem rot.     

Association of Puroindoline b-B2 variants with grain traits,yield components and flag leaf size in bread wheat (Triticum aestivum L.) varieties of the Yellow and Huai Valleys of China

A total of 169 wheat (Triticum aestivum L.) varieties (landraces and cultivars) were used to asses the relationship between Puroindoline D1 alleles and Puroindoline b-B2 variants and grain hardness, other grain traits, yield components, and flag leaf size. Results indicated that the average SKCS hardness of Pinb-B2v3 varieties was significantly greater than that of Pinb-B2v2 varieties within the soft Puroindoline D1 haplotype sub-group. Conversely, no statistically significant difference was obtained for SKCS hardness between varieties with the Pinb-B2v3 vs. Pinb-B2v2 alleles within the two hard Puroindoline D1 haplotypes (Pinb-D1b and Pinb-D1p sub-groups). Therefore, the Puroindoline b-B2 gene may have a bigger impact on soft wheat varieties than hard. Across all varieties, thousand-kernel weight, grain weight per spike, grain diameter, grain number per spike, flag leaf width and area of Pinb-B2v3 varieties were significantly greater than those possessing Pinb-B2v2. These results indicated that the Pinb-B2v3 allele was associated with preferable grain yield traits compared to the Pinb-B2v2 allele in bread wheat. This study provides evocative information for better understanding the molecular and genetic basis of wheat grain yield.     

Effect of the grain protein content locus Gpc-B1 on bread and pasta quality

Grain protein concentration (GPC) affects wheat nutritional value and several critical parameters for bread and pasta quality. A gene designated Gpc-B1, which is not functional in common and durum wheat cultivars, was recently identified in Triticum turgidum ssp. dicoccoides. The functional allele of Gpc-B1 improves nitrogen remobilization from the straw increasing GPC, but also shortens the grain filling period resulting in reduced grain weight in some genetic backgrounds. We developed isogenic lines for the Gpc-B1 introgression in six hexaploid and two tetraploid wheat genotypes to evaluate its effects on bread-making and pasta quality. In common wheat, the functional Gpc-B1 introgression was associated with significantly higher GPC, water absorption, mixing time and loaf volume, whereas in durum wheat, the introgression resulted in significant increases in GPC, wet gluten, mixing time, and spaghetti firmness, as well as a decrease in cooking loss. On the negative side, the functional Gpc-B1 introgression was associated in some varieties with a significant reduction in grain weight, test weight, and flour yield and significant increases in ash concentration. Significant gene × environment and gene × genotype interactions for most traits stress the need for evaluating the effect of this introgression in particular genotypes and environments.     

A set of near-isogenic lines for blast resistance genes with an Indica-type rainfed lowland elite rice (Oryza sativa L.) genetic background

A set of near-isogenic lines for blast resistance genes was developed by using an Indica-type elite rice variety, IR49830-7-1-2-2, suitable for the rainfed lowland conditions in the tropics, as a genetic background. Initially, we revealed that IR49830-7-1-2-2 harbors five blast resistance genes - Pia, Pib, Pik-s, Pita, and Pi11(t) - by using a differential system involving 19 selected standard blast isolates from the Philippines. Based on this result, we developed nine near-isogenic lines (NILs) targeting eight resistance genes - Pik, Pi7(t), Pi3, Pi5, Pita-2, Piz-5, Pish, and Pi9 - by recurrent backcrossing. The introgression of each resistance gene in the NILs was confirmed by reaction patterns to the blast isolates, allelism tests, and DNA marker analysis. In addition, a genome-wide DNA marker survey revealed that most of the chromosome regions in each NIL were of the IR49830-7-1-2-2 type. The agricultural characteristics of most of the developed NILs were almost the same as those of IR49830-7-1-2-2. Moreover, with one exception, they showed submergence tolerance similar to IR49830-7-1-2-2. The developed NILs could be used as a multiline variety suitable for the rainfed lowland in the tropics.     

Effects of the replacement of Glu-A1 by Glu-D1 locus on agronomic performance and bread-making quality of the hexaploid wheat cv. Courtot

The aim of this study was to evaluate the cumulative and interactive effects on wheat (Triticum aestivum L.) gluten strength and mixing properties of dough associated with the duplication of the Glu-D1 locus. A partially isohomoeoallelic line RR240, in which a segment of the wheat chromosome 1D containing the Glu-D1 locus encoding the Dx2 + Dy12 subunits and translocated to the long arm of the chromosome 1A through homoeologous recombination, was assessed. Agronomic traits and yield components were studied in the translocated line RR240 and compared with the control line cv. Courtot. Both lines were evaluated under field conditions in two experimental years. Technological effects resulting from the duplication of HMW glutenin subunits Dx2 and Dy12 were evaluated using the Alveograph test, the Mixograph test and the baking test. The RR240 line was shown to have a lower agronomic performance for 1000-kernel weight and grain yield. However the duplication of the Glu-D1 allele was associated with a significant effect on dough strength and mixing resistance, and on the Zeleny sedimentation volume. Baking parameters were not significantly modified between both lines although the score values of the CNERNA test were observed to be slightly higher in RR240 than in Courtot.     

Transgressive variants for red pericarp grain with high yield potential derived from Oryza rufipogon × Oryza sativa: Field evaluation, screening for blast disease, QTL validation and background marker analysis for agronomic traits

Five transgressive variants (advanced breeding lines from BC₂F₅ and BC₂F₆ generation) were derived from a cross between the wild relative, O. rufipogon Griff. and O. sativa L. subsp. indica cv. MR219, a popular high yielding Malaysian rice cultivar. The aim of the study was to evaluate the pericarp colour of the grains along with yield potential and to validate quantitative trait loci (QTLs) for agronomic traits. The variants were screened against blast disease. Background marker analysis was also done for the promising variants. The field trials were carried out at a single location (due to containment purposes) over two seasons using randomized complete block design (RCBD) with three replications. A trait-based marker analysis was used to identify QTLs for validation in BC₂F₅ generation. Analysis of variance (ANOVA) showed that the seasonal factors influenced different agronomic traits. Variant G33 produced significantly (p < 0.05) higher yield (5.20 t/ha) than the control, MR219 (4.53 t/ha). Eighteen QTLs for different agronomic traits were identified in BC₂F₂ population in a previous study. Among them 14 QTLs were found in BC₂F₅ population of the present study. The yield of variant G33 was influenced by several QTLs viz. qGPL-1, qSPL-1-2, qSPL-8 and qYLD-4, which were introgressed from the donor parent revealed by background marker analysis using BC₂F₇ generation. Percentage (99%) of red pericarp grain of G33 and G34 in BC₂F₅ and BC₂F₆ generations indicated the stability of pericarp colour which was transferred from the wild relative. Variant G33 showed resistance against two pathotype of blast disease (Magnaporthe oryzae). Among the evaluated variants, G33 could be considered for inclusion in the cultivar development program for red rice with high yield potential and resistance to blast disease. This study demonstrated that the alleles from wild relative could improve the yield and yield related traits through allelic interaction, even though the phenotypic traits were inferior to the recurrent parent.     

Effect of the thermostable xylanase B (XynB) from Thermotoga maritima on the quality of frozen partially baked bread

The effect of the recombinantly produced xylanase B (XynB) from Thermotoga maritima MSB8 on the quality of frozen partially baked bread (FPBB) was investigated. Addition of XynB to wheat flour dough resulted in a significant increase in dough extensibility (L), swelling (G), and a decrease in dough resistance to deformation (P), configuration. Bread crumb characteristics were studied by differential scanning calorimeter (DSC) and dynamic-mechanical analysis (DMA). The results show that addition of XynB leads to improvements in the bread quality of FPBB and retards bread staling compared to the control. The greatest improvements were obtained in specific volume (+35.2%) and crumb firmness (−40.0%). The control FPBB was significantly firmer in texture and higher in amylopectin recrystallization than the bread with XynB. During frozen storage of FPBB with and without XynB for 8 weeks, the crumb firmness increased gradually and the specific volume slightly decreased with the frozen storage time. The ΔH values of freezable water (FW) endothermic transitions increased with frozen storage time for all samples. However, addition of XynB lowered the ΔH values indicating a decrease in FW. Therefore, XynB is useful in improving the quality of FPBB. DMA was also used to monitor the shrinking behavior of the samples. Addition of XynB increased the contraction during chilling but significantly diminished the total shrinking and frozen-state shrinking of the bread crumb during the freezing process.     

Effect of salinity on yield and 2-acetyl-1-pyrroline content in the grains of three fragrant rice cultivars (Oryza sativa L.) in Camargue (France)

Aromatic quality of rice grains is known to vary greatly with environmental factors and cultivation methods. Among the environmental factors, soil salinity is thought to have a positive impact on the content of 2-acetyl-1-pyrroline (2AP) in grains, the key volatile compound of rice aroma. This study compared 2AP content in grains of three improved fragrant rice (Oryza sativa L.) varieties grown in two fields, differing mainly in their soil salinity level. The impact of salinity on yield and main yield components was also investigated to understand the relationship between aromatic quality and yield build-up. Soil salinity was monitored by measuring the electrical conductivity (EC) of soil solution samples extracted every week. 2AP content in grains was determined by a newly developed stable isotope dilution method involving solid-phase microextraction (SPME) and GC MS/MS analysis. The results showed an increase of 2AP content in grains with salinity for the three varieties. The relationship between 2AP and mean EC of the crop fitted a single model for the three varieties (R² = 0.728). In contrast, the impact of salinity on yield and yield components differed greatly between the three varieties. One variety appeared to be very sensitive to salt stress, with significant yield loss up to 40%, while the two other varieties proved to be resistant to the salinity levels experienced by the plants, with no significant yield loss or even higher yields in saline conditions. Nevertheless, the three varieties presented a significant negative correlation between 1000 grain weight (TGW) and the mean EC of the crop, and between TGW and 2AP content. It was concluded that the increase of 2AP content with salinity resulted partially from a 2AP concentration mechanism in smaller size grains. The direct effect of salinity on 2AP synthesis through stimulation of the proline metabolism is further discussed.     

Waxy gene haplotypes: Associations with apparent amylose content and the effect by the environment in an international rice germplasm collection

Apparent amylose content (AAC), the key determinant of rice end-use quality attributes, is primarily controlled by the Waxy gene which codes for granule bound starch synthase (GBSS). We examined the combination of sequence variation in the Waxy gene and environmental effects, and their associations with AAC using 171 rice accessions originating from 43 countries. The combination of two single-nucleotide-polymorphism (SNP) markers in the Waxy gene allows for the identification of three marker haplotypes in this gene. The first SNP is at the leader intron splice site (In1 SNP), and the second polymorphism is in exon 6. The haplotypes explained 86.7% of the variation in AAC and discriminated the three market classes of low, intermediate and high AAC rice from each other. The environment affected the AAC of all haplotypes. Higher air temperature during grain development associated with a decrease in AAC of low and intermediate AAC-types, but with an increase in AAC of high AAC-type. The association of AAC with several Waxy RM190 microsatellite-(CT_n) alleles in combination with the In1 SNP was also examined. In conclusion, the Waxy haplotypes studied appear to be useful markers for selecting the AAC of breeding lines developed from the world's rice germplasm.