【Short Report】Identification of Chromosome Regions Affecting Leaf Area with Rice Chromosome Segment Substitution Lines

Abstract

The aim of this study was to obtain the information for improvement in source ability via expansion of a flag leaf area in rice (Oryza sativa L.). We identified chromosome regions affecting a trait (CRATs) for leaf area and confirmed their effects with two sets of chromosome segment substitution lines developed from indica landraces Kasalath or Nona Bokra as a donor under japonica cultivar Koshihikari genetic background. We detected 4 and 8 CRATs that increased leaf area by Kasalath and Nona Bokra alleles, respectively. With the Nona Bokra allele, CRAT on chromosome 7 (LA7) increased leaf area by 54% comparing to Koshihikari. LA7 maintained the contents of Rubisco and photosynthetic rate and as a result its “estimated” source ability of a flag leaf was increased by 23%. The effect of LA7 was stable under different environmental conditions, and might be useful for breeding rice with higher source ability and yield.     

【Short Report】Influence of the Improved System of Rice Intensification (SRI) on Rice Yield,Yield Components and Tillering Characteristics under Different Rice Establishment Methods

Abstract

The impacts of the system of rice intensification (SRI) and conventional management (CM) on grain yield, yield components and tillering capacity were examined under 4 rice establishment methods transplanting (TP), seedling casting (SC), mechanical transplanting (MT) and direct seeding (DS). SRI produced significantly higher grain yield than CM under TP and MT but not under DS or SC. DS and SC produced much higher seedling quality than TP or MT, suggesting that robust seedlings with vigorous roots weaken the positive effect of SRI on rice yield. SRI produced a higher tillering rate than CM, but did not affect ear-bearing tiller rate significantly. Moreover, the net photosynthetic rate of the recent fully expanded leaf at mid-tillering stage was significantly higher in SRI than in CM under MT and TP. The obtained results also indicated that SRI increased biomass accumulation before heading and improved utilization of photosynthates in the grain-filling stage.     

Effect of Rolled Leaf Gene Rl（t） on Grain Quality in Hybrid Rice

Effects of rolled leaf gene Rl（t） on grain quality characters of hybrid rice were analyzed by using three pairs of rolled leaf near-isogenic lines under two fertilizer treatments. Under normal fertilizer level （e.g. 450 kg urea per ha）, head rice rates and milled rice recovery of rolled leaf hybrids were significantly higher than those of corresponding non-rolled crosses, while the chalky rice rate and chalkiness were all lower. Of the RVA profiles, the peak viscosity, the hot paste viscosity and the breakdown viscosity of the rolled were all higher than those of the corresponding non-rolled ones to various degrees. Increasing fertilizer application for promoting panicle development increased the brown, milled and head rice rates except for Shanyou 63, furthermore, significant difference of head rice rates existed between the rolled leaf Shanyou 559 and Shanyou 559; while the peak viscosity, the hot paste viscosity and the breakdown viscosity all decreased to different levels; changes of values of other characters had no apparent regularity. It suggested that Rl（t） could improve rice quality under certain conditions.     

Farmers’ Management Practices and Grain Yield of Rice in Response to Different Water Environments in Kamping Puoy Irrigation Rehabilitation Area in Northwest Cambodia

Abstract

The farmers’ management practices and grain yield were examined in the consecutive 4 cropping seasons from wet season rice (WSR) in 2008 to dry season rice (DSR) in 2010 across upstream, midstream and downstream fields, along two secondary drainage canals (located either upstream or downstream side along the main canal) in the Kamping Puoy Irrigation Rehabilitation area (KPIR). In WSR, standing water depth was much deeper in downstream fields where medium and late maturing varieties were planted from May than in upstream fields where early and early medium maturing varieties were planted later (mostly in July and August). In DSR there was less difference in water conditions between upstream and downstream fields and variation in planting and harvesting time was small. As the area percentage of fields where DSR was introduced increased from 2008 (54%) to 2010 (100%), planting time in WSR was later (e.g., from May to July) with declining proportion of dry seeding method and mid-season tillage. Grain yield was low in DSR, particularly in 2010 (287 and 247 g m-² in 2009 and 2010 on average, respectively), due to insufficient weed control and small amount of fertilizer, and the yield was lowest in fields which practiced DSR for the first time. Grain yield in WSR (286 and 291 g m-² in 2008 and 2009 respectively) increased by transplanting, use of high yielding Raing Chey variety, and application of a larger amount of N chemical fertilizer. These findings indicated that the agriculture extension support to farmers, particularly in DSR, is a key important factor for rice yield improvement in KPIR.     

Difference in Grain Yield and Quality among Tillers in Rice Genotypes Differing in Tillering Capacity

A japonica variety and its iso-allelic mutant with high tillering ability were used to investigate the differences in grain yield and quality among different tillers. There was a distinct difference in panicle weight among tillers during grain filling for both genotypes, with Xiushui 11 having a greater increase rate in panicle weight, and being earlier in reaching the maximum panicle weight than the mutant. There was a great significant difference between the two genotypes in grain yield and its components, with Xiushui 11 having higher grain yield, more grains per panicle, higher filled grain percentage and grain weight than the mutant for each type of tiller. Moreover, a significant difference was found in grain yield and yield components among different tillers for both genotypes, with grain number per panicle showing the greatest variation over tillers among all yield components. Compared with Xiushui 11, the mutant had higher brown rice rate and greater ratio of length to width of brown rice, and lower chalky rice rate, amylose content, and protein content of rice. Furthermore, there was a significant difference in grain quality among tillers within a plant for both genotypes, with later initiated tillers being lower in chalky rice rate, amylose and protein contents than early initiated ones. The variation of most quality parameters among tillers within a plant was markedly larger for the mutant than for Xiushui 11.     

【Short Report】Allelopathic Potential of White,Red and Black Rice CultivarsHisashi Kato-Noguchi1, Kenji Nitta2 and Tomio Itani2

Abstract

The inhibitory effect (allelopathic potential) of shoot, seed and root extracts of 8 white, 5 red and 5 black rice (Oryza sativa L.) cultivars was determined against the seedling growth of lettuce (Lactuca sativa L.) and white clover (Trifolium repens L.). All extracts inhibited hypocotyl and root growth of lettuce and white clover seedlings, and those inhibitory activities ranged from –1% – 96%. The average inhibitory activity of the extracts on the hypocotyl and root growth of lettuce and white clover was 42 – 88%. No apparent difference in the inhibitory activity was found either among the extracts of white, red and black rice, or among the extracts of shoots, seeds and roots. However, the red rice cultivar Tsushima-akamai marked the greatest inhibitory activity with an average of 88% growth inhibition on hypocotyls and roots of lettuce and white clover, followed by Souja-akamai and Koshihikari. These results suggest two red rice, Tsushima-akamai and Souja-akamai, may be potentially useful for weed management in agriculture.     

Effects of Soil Copper Concentration on Growth, Development and Yield Formation of Rice （Oryza sativa）

Pot experiments were conducted in 2002 and 2003 to investigate the effects of soil copper（Cu） concentration on growth, development and yield formation of rice by using the japonica cultivar Wuxiangjing 14 and hybrid rice combination Shanyou 63. The plant height, leaf number, elongated internode number and heading date of rice plants were not affected at soil Cu levels below 200 mg/kg, but affected significantly at above 400 mg/kg. The inhibitory effects on rice growth and development were increased with the increment of soil Cu levels. The grain yields decreased significantly with raising soil Cu levels. The main reasons for the grain yield reductions under lower soil Cu levels （100, 200 mg/kg） were mainly due to the decrease of number of spikelets per panicle, however, under higher soil Cu levels （more than 400 mg/kg）, both panicle number and number of spikelets per panicle contributed to the yield loss. The decreases of panicle number by Cu stress were mainly attributed to slow recovery from transplanting, delayed tillering and reduced maximum tiller numbers. The reduction of number of spikelets per panicle under soil Cu stress resulted from the decreases of both shoot dry weight （SDW） at the heading date and the ratio of spikelets to SDW. Total biomass at maturity decreased significantly with the increase of soil Cu levels, while economic coefficient showed non-significant decrease except under soil Cu levels above 800 mg/kg.     

Effect of System of Rice Intensification on Grain Plumpness in Association with Source-Sink Ratio in Mid-Season Hybrid Rice

Grain plumpness under two cultivation methods, the system of rice intensification(SRI) and traditional cultivation, was examined using 18 mid-season hybrid rice combinations. There existed a highly significant negative correlation between the differences of grain plumpness under the two cultivation methods and number of spikelets per panicle. The small- or middle-panicle type hybrid rice though they showed a significant decrease in leaf-grain ratio under SRI maintained normal grain filling due to plenty of source supply, while the large-panicle hybrid rice was on the contrary. It suggested that the number of spikelets per panicle below 173 under traditional cultivation, was an index for selecting variety in application of SRI in the southern region of Sichuan Province, China.     

Effects of Rice Variety and Growth Location in Cambodia on Grain Composition and Starch Structure简

The effects of variety and growth location on grain composition and starch structures were investigated using three rice (Oryza sativa L.) cultivars (Phka Romduol, Sen Pidao and IR66) with different amylose contents. All the three cultivars were planted in three different agro-climatic zones (Phnom Penh, Coastal and Plateau) of Cambodia. The protein content of polished grains increased when rice was planted at a location with higher average temperature, but their lipid content decreased. The amylose content and degree of branching were not greatly affected by the minor temperature differences among the growing locations. Starch fine structures characterized by the chain-length distribution were significantly different among the cultivars, but not significantly among different locations. The results suggested that protein and lipid biosyntheses were more sensitive to the environmental temperature than that of starch in rice grains.     

Effects of Seeding Rate and Nitrogen Application Rate on Grain Yield and Protein Content of the Bread Wheat Cultivar ‘Minaminokaori’ in Southwestern Japan

Abstract

We examined the effects of seeding rate, 50 or 150 seeds m-², nitrogen (N) application rate at active tillering and jointing, 4 and 2 g N m-², respectively, or none, and N application rate at anthesis, 0, 2, 4, or 6 g N m-², on grain yield and protein content of a bread wheat cultivar, ‘Minaminokaori’, during the 2004–2005 crop season in southwestern Japan. Grain yield was similar at a seeding rate of 50 and 150 seeds m-². It was higher when 4 and 2 g N m-² were applied at active tillering and jointing, respectively (4–2N), than when no N was applied at these stages (0–0N). However, it was not influenced by N application rate at anthesis. Grain protein content was similar at 50 and 150 seeds m-². It was higher in 4–2N than in 0–0N. It was the highest when 6 g N m-² was applied at anthesis, followed by 4, 2, and 0 g N m-². The SPAD value at anthesis was higher at 50 than 150 seeds m-², but leaf area index (LAI) at anthesis was similar at 50 and 150 seeds m-² and protein content of grain was nearly the same at 50 and 150 seeds m-² irrespective of N application rate at anthesis. LAI and the SPAD value were higher in 4–2N than in 0–0N and the protein content of grain was also higher in 4–2N than in 0–0N irrespective of N application rate at anthesis. Therefore, both LAI and the SPAD value may be important traits related to the N application rate at anthesis suitable for yielding wheat grain with a high protein content.     

【Short Report】Alternative Experimental Method Using a FRP Pot for Evaluating Wet Damage in Soybean and Morning Glory Grown underExcess Soil Water Conditions

Abstract

A fiber reinforced plastic (FRP) pot, equipped with a slanted pipe through which water is supplied, has been used for assessment of rice herbicides. This pot may also be useful for controlling water table in upland conditions. In this experiment, early growths of soybean and morning glory grown under waterlogging and excess soil water conditions were evaluated. The waterlogging condition was attained by adjusting the top of the slanted pipe to soil surface level, and excess soil water condition (0.2 m³ m^?3) by adjusting to 15 cm below the soil surface. The water content of the soil did not fluctuate during the treatment. Shoot growths of soybean and morning glory were poorer under waterlogging than excess soil water condition. The present experimental procedures using a FRP pot could be available for evaluation of wet damage of field crops grown under ill-drained field.     

Comparison of Grain Quality Characteristics Between F1 Hybrids and Their Parents in Indica Hybrid Rice

Sixteen widespread elite indica parents including seven CMS lines and nine restorer lines, and their 63 F1 hybrids were chosen to compare the eleven traits of grain quality. Overall results showed that the frequency of negative over dominance, dominance and partial dominance was much higher than that of positive ones and heterosis, indicating that the values of F1 hybrids were generally lower than the means of their parents in quality characteristics. There existed apparent disparity in grain quality performance among F1 hybrids varied with the traits. The characteristics of chalky area percentage, chalky grain percentage, gel consistency and head rice recovery had a great variation in all kinds of tested heterosis indices including the mid parent heterosis index, over high value parent heterosis index and over low value parent heterosis index, which suggested that special attention should be paid to the selection of F1 hybrids in these traits in breeding. The mean values of F1 hybrids were significantly lower than those of their higher parents in all the traits but close to or significantly lower than those of their mid parent values except for kernel length and amylose content; and significantly higher than those of their lower parents except for brown rice recovery, milled rice recovery and gel consistency.     

Influence of Rice Genotypes on Folding and Spinning Behaviour of Leaffolder （Cnaphalocrocis medinalis） and Its Interaction with Leaf Damage

Folding and spinning behavior of Cnaphalocrocis medinalis （Guenee） （Lepidoptera： Pyralidae） in different categories of rice genotypes viz., resistant, susceptible, hybrid, scented, popular and wild rice genotypes were significantly different. Longer leaf selection time and folding time per primary fold; shorter primary fold and whole leaf fold; lower number of binds per primary fold and whole leaf fold were recorded in resistant and wild rice genotypes. In the correlation analysis, it was found that the leaf folding parameters were positively correlated to leaf folder damage whereas the leaf spinning parameters were negatively correlated. Similarly, the morphological characters differed significantly among the chosen genotypes and were related to leaffolder damage. The leaf width and total productive tiller number were positively correlated to leaffolder infestation. Results also indicated that the trichome density and length, leaf length and plant height might contribute to resistance whereas total number of green leaves had no effect on leaffolder infestation. In the scatter plot analysis between leaf folding and spinning characters and leaffolder damage, the genotypes were separated into four groups viz., resistant （TKM6, Ptb 33, LFR831311, Oryza rhizomatis and O. minuta）, moderately resistant （ASD16 and CORH1）, moderately susceptible （ADT36, Pusa Basmati and CB200290） and susceptible （IR36 and TN1）. The present investigation proved that the leaf morphology viz., leaf length and width, plant height and trichome density and length may play a vital role in resistance against rice leaffolder.     

Genetic Analysis and Mapping of Dominant Minute Grain Gene Mi3（t） in Rice

Grain size, determined chiefly by grain length, is one of the main factors affecting the grain yield in rice production. To study the trait of rice grain size, F1 and F2 populations were developed from crosses Shuhui 881/Y34 and Shuhui 527/Y34, and genetic analysis for minute grain was performed. The F1 populations showed minute grains, and grain size segregations in the two F2 populations were both in accordance with the ratio of 3：1, indicating that minute grain in Y34 was controlled by a completely dominant gene. By using the F2 population from Shuhui 881/Y34, this dominant gene, tentatively designated as Mi3（t）, was mapped based on SSR markers in the interval between RM282 （genetic distance of 5.1 cM） and RM6283 （genetic distance of 0.9 cM） on the short arm of chromosome 3.     

Comparison of Grain Quality Characteristics Between F1 Hybrids and Their Parents in Indica Hybrid Rice

Sixteen widespread elite indica parents including seven CMS lines and nine restorer lines, and their 63 F1 hybrids were chosen to compare the eleven traits of grain quality. Overall results showed that the frequency of negative over-dominance, dominance and partial dominance was much higher than that of positive ones and heterosis, indicating that the values of F1 hybrids were generally lower than the means of their parents in quality characteristics. There existed apparent disparity in grain quality performance among F1 hybrids varied with the traits. The characteristics of chalky area percentage, chalky grain percentage, gel consistency and head rice recovery had a great variation in all kinds of tested heterosis indices including the mid-parent heterosis index, over high-value parent heterosis index and over low-value parent heterosis index, which suggested that special attention should be paid to the selection of F1 hybrids in these traits in breeding. The mean values of F1 hybrids were significantly lower than those of their higher parents in all the traits but close to or significantly lower than those of their mid-parent values except for kernel length and amylose content; and significantly higher than those of their lower parents except for brown rice recovery, milled rice recovery and gel consistency.     

Effects of Different Nitrogen Fertilizer Levels on Fe, Mn, Cu and Zn Concentrations in Shoot and Grain Quality in Rice （Oryza sativa）

In a pot experiment, effects of N fertilizer application on the concentrations of Fe, Mn, Cu and Zn in shoot of rice and the quality of brown rice were studied. In the treatments with N fertilizer application, the concentrations of Fe, Mn, Cu and Zn in most parts of rice shoot increased compared with control (no N fertilizer application). This indicated that the transportation ability of microelements from root to shoot in rice was improved with N fertilizer application. Effect of N fertilizer on IR68144 was similar to that of on IR64, but the concentrations of the microelements in plant differed, suggesting that the characteristic expression of the two rice genotypes was not controlled by the amount of N fertilizer supplied. The concentrations of those microelements in brown rice increased at first and then decreased with increasing N fertilizer application, reaching the highest at 160 kg/ha, at which the Fe, Mn, Cu and Zn concentrations in brown rice increased by 28.96%, 41.34%, 58.31% and 16.0% for IR64, and by 22.16%, 13.75%, 8.75% and 20.21% for IR68144 compared with control, respectively. Moreover, N fertilizer promoted the accumulation of protein, decreased the accumulation of amylose in grain, and enhanced gel consistency of brown rice. These results indicate that appropriate N fertilizer management could increase micronutrient contents in grain and improve nutrition quality of rice.     

Effect of Indica Rice Diets Supplemented with Exogenous Enzyme on Growth and Digestion of Pigs Fed Paddy-Based Diets

Sixty growing pigs (Landrace × Jiaxing black) were used to study the effects of exogenous enzymes (including β-glucanase, xylanase and cellulase) supplemented to paddy-based diets on pig growth performance and digestion. With the supplementation of enzymes, average daily gain of pig was increased by 8.78%(P<0.05), feed gain radio was decreased by 9.42%(P<0.05), feed apparent digestibilities of crude protein, crude fat and crude fiber were increased by 17.32% (P<0.01), 16.04% (P<0.05) and 108.57%(P<0.01), the viscosity of jejunum, and ileum contents were reduced by 7.08%(P<0.01) and 6.78%(P<0.01), numbers of E. coli in feaces and diarrhoea morbidity were decreased by 81.29%(P<0.01) and 37.00%(P<0.05), and the activities of protelytic enzyme and a-amylase in duodenal contents were enhanced by 99.07% (P<0.05) and 18.38%(P<0.05), respectively.     

Effects of Bicarbonate and High pH Conditions on Zinc and Other Nutrients Absorption in Rice

Zinc deficiency was widely observed in calcareous soil where bicarbonate and high pH were always related with low zinc availability. In a hydroponic experiment, one zinc-efficient rice (IR36) and one zinc-inefficient rice (IR26) genotypes were employed to investigate the effects of bicarbonate and high pH conditions on absorption, transport of zinc and other nutrients (P, K, Ca, Mg, Fe, Cu, Mn) in rice. As compared with the control, high pH inhibited absorption, translocation and accumulation of zinc and other nutrients in both rice genotypes. Bicarbonate had minor effect on zinc-efficient rice genotype (IR36) whereas it could decrease zinc and other nutrient absorption in zinc-inefficient rice genotype (IR26). These results implied that increasing rice tolerance to bicarbonate is one of the most important strategies to improve rice adaptation for zinc-deficit calcareous soil.     

Grain Quality and Genetic Analysis of Hybrids Derived from Different Ecological Types in Japonica Rice （Oryza sativa）

The performance and inheritance of 7 quality traits were studied using F2 rice grain derived from 8×8 diallel crossing made by employing 8 parents of different ecological japonica rice types. Differences in each trait among 8 parents were not obvious, but in F2 generation, transgressive phenomena were found in all the traits studied, indicating that the genes controlling these traits among parents were segregated. The inheritance of grain width, grain weight, chalkiness score (CS), gelatinization temperature (GT) and gel consistency (GC) were suitable to additive-dominant model, and dominant effect contributed mainly for the 5 traits. The inheritance of grain length (GL) and amylose content (AC) did not fit into additive-dominant model, existing epistatic interactions. Dominant genes for grain width and grain weight had the efficiency of decreasing effect, and dominant genes for CS, GT and GC had the efficiency of enhancing effect. Koshihikari contained more recessive genes for gelatinization temperature than other varieties. Zhendao 88 had more dominant genes in grain width and grain weight than other varieties. Xiushui 04 possessed more dominant genes for GL and GC, and more recessive genes for CS than other varieties.     

Analysis of QTLs for Flag Leaf Shape and Its Response to Elevated CO2 in Rice （Oryza sativa）

To understand the responses of flag leaf shape in rice to elevated CO2 environment and their genetic characteristics,quantitative trait loci(QTLs)for flag leaf shape in rice were mapped onto the molecular marker linkage map of chromosome segment substitution lines(CSSLs)derived from a cross between a japonica variety Asominori and an indica variety IR24 under free air carbon dioxide enrichment(FACE,200μmol/mol above current levels)and current CO2 concentration(Ambient,about 370μmol/mol).Three flag-leaf traits,flag-leaf length(LL),width(LW)and the ratio of LL to LW (RLW),were estimated for each CSSL and their parental varieties.The differences in LL,LW and RLW between parents and in LL and LW within IR24 between FACE and Ambient were significant at 1%level.The continuous distributions and transgressive segregations of LL,LW and RLW were also observed in CSSL population,showing that the three traits were quantitatively inherited under both FACE and Ambient.A total of 16 QTLs for the three traits were detected on chromosomes 1,2,3,4,6,8 and 11 with LOD(Log10-likelihood ratio)scores ranging from 3.0 to 6.7.Among them,four QTLs (qLL-6*,qLL-8*,qLW-4*,and qRLW-6*)were commonly detected under both FACE and Ambient.Therefore,based on the different responses to elevated CO2 in comparison with current CO2 level,it can be suggested that the expressions of several QTLs associated with flag-leaf shape in rice could be induced by the high CO2 level.