To clarify the genotypic variation of nitrogen (N) response in the AA genome Oryza species, we investigated dry matter production, N uptake, N and water use efficiencies (NUE and WUE), bleeding sap rate (BR), and root morphological traits at vegetative stage in 6 cultivars and 4 strains of 6 species (O. sativa, O. glaberrima, O. barthii, O. nivara, O. meridionalis, and O. rufipogon) grown under standard N (SN) and low N (LN) conditions. Some wild Oryza strains and O.glaberrima showed high dry matter production under both N conditions. In most plants, total dry weight decreased and root dry weight increased under the LN condition, resulting in decreased top-root ratio. In japonica cultivars of O. sativa, however, these traits were unaffected by the N condition. There were no significant differences in WUE with plant species or N conditions. In all plants, however, NUE was higher in the LN than SN condition, and was conspicuously high in most wild Oryza species and O. glaberrima. Some of them showed increased capacity of nitrate-N (NO3-N) uptake under the LN condition. In cultivars and strains with a high NUE, root dry weight, root surface area, and BR were also higher under the LN condition. These results suggest that a high NUE is associated with the development of a root system, increased BR, and probably increased capacity of NO3-N uptake. This study revealed the presence of superior wild Oryza strains for growth under LN that may be a promising genetic resource for low N-input agriculture.
Barley (Hordeum vulgare L.) plants accumulate glycine betaine (GB), a major compatible solute, in response to salt stress. In barley, GB is produced by a two-step oxidation of choline in a cooperative way in the cytosol and peroxisomes. In this study, we investigated the localization of two GB biosynthetic enzymes, choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH), in the tissues of barley plants (cv. Haruna-nijyo) grown under normal and saline conditions. Three-week-old barley plants grown hydroponically were treated with a hydroponic culture solution containing 200 mM NaCl for 72 h. Salt treatment resulted in increased expression of CMO and BADH proteins mainly in the leaves of barley but not in the roots. The expression of CMO protein was increased by the presence of NaCl in younger leaves but decreased in older leaves. The tissue localization of CMO and BADH proteins was analyzed by immunofluorescent labeling method using their primary antibodies and a fluorescein-conjugated secondary antibody. CMO and BADH proteins were constitutively co-localized in mesophyll and bundle sheath cells under both normal and saline conditions. A possible physiological function of GB in the salt tolerance of barley plants is discussed.
In southwestern Japan, late sowing of soybean is an option that may avoid the damage caused by excessive soil moisture during the rainy season. We investigated the adaptability to late sowing using 17 genotypes from 5 countries. The seeds were sown on 15–20 July, and 2–5 August in the normal and late sowing seasons, respectively, in an upland field in Karatsu, southwestern Japan in 2009, 2010 and 2011. Late sowing reduced the seed yield by 28.1% and 21.8% on average in the 2009 and 2011 experiments, respectively, whereas it had almost no effect in 2010, in which the temperature was high from sowing to flowering. Seed yield was not improved by increasing the growth period with a longer juvenile growth stage in the genotypes that originated in tropical areas. In the late sowing, seed yield was significantly correlated with the reproductive period from flowering to maturity and pod number, but not with the vegetative period from sowing to the end of leaf expansion or seed size. Soybean cultivars Caviness (USA), Parana and IAS-5 (Brazil), and Akisengoku and Akiyoshi (Japan) showed higher productivity in both types of sowing season, and their seed yields were less reduced by late sowing. These genotypes generally have larger pod number and seed number or longer seed filling periods, but they have medium-size seeds. Our results indicate that the seed yield in late sowing could be improved by the selection of adaptive genotypes that have larger seed number and/or longer seed filling periods.
Using backcross inbred lines (BILs) derived from a cross between temperate japonica rice cultivars, Moritawase and Koshihikari, we validated the major quantitative trait loci (QTL) for eating quality and textural characteristics on chromosomes (Chr) 1, 2, 3, 6, 7, 10, and 12. Significant genetic differences in eating quality among BILs were detected at the QTL on Chr 3 and corresponded to the differences between the parents. Although differences in eating quality on the other chromosomes were not significant by t-test, cluster analysis and principal component analysis clearly showed that the genetic effects of the QTLs on Chr 6, 7, and 10 were similar to that on Chr 3, but the genetic effects of QTLs on Chr 1, 2, and 12 were entirely different from that on Chr 3. We previously identified that textural characteristics were highly correlated with eating quality. In this study, genetic differences in textural characteristics were similar to the genetic differences in eating quality among BILs. These results reveal major QTLs for eating quality of Koshihikari on Chr 3, 6, 7, and 10. The QTL on Chr 3 contributed most to the improvement of eating quality and textural characteristics.
The cultivars of NERICA (New Rice for Africa), which are characterized by early maturity and high yield potential under rainfed conditions, have the potential to increase rice production in Tanzania, where rice cultivation is greatly affected by a short rainy season. Trials were conducted in Zanzibar to examine the yield performances of 14 NERICA cultivars at five locations during the long-rains season (Masika) and at another five locations during the short-rains season (Vuli). The NERICA cultivars produced significantly higher yields than local cultivars at five locations. Yields of 12 NERICA cultivars were associated with rainfall (R2=0.367 to 0.732) such that they yielded well during Masika (109 to 343 g m-2) and poorly during Vuli (11 to 68 g m-2). Spikelet number per panicle and percentage of filled spikelets (% filled spikelets) accounted for 70 to 90% of the yield variation in all cultivars, suggesting that yield was determined mainly during the later part of the growth period. In some cultivars, yield was associated with rainfall during the later part of the growth period but the yield of the remainder was associated with rainfall during the early part. A selected group of farmers, extension workers and researchers evaluated grain quality. Some cultivars scored well, especially NERICA 1. We conclude that NERICAs are generally suitable for production during Masika and that NERICA 1 especially should be promoted due to its high grain quality. However, for double cropping of NERICAs, measures must be implemented for increasing or maintaining the water status of the soil during Vuli.
A field experiment assessing the effect of the annual application of anaerobically-digested cattle manure (ADM), produced at a biogas plant, on paddy rice was conducted. In plots with ADM (MF), the early growth of rice plants, from transplanting to the active tillering stage, was inhibited compared to the plots with chemical fertilizers (CF). This phenomenon was observed over many growing seasons and was especially obvious in nitrogen uptake and leaf area index (LAI). However, after panicle initiation, the growth of MF-treated plants was equal to or superior to CF-treated plants. The grain yield in all the MF plots was 96–105% of that in the CF plots. The inorganic nitrogen content of the soil in the MF plots was higher than that in the CF plots, which was contradictory to the growth inhibition observed in the initial growth of plants in the MF plots. In contrast, the oxidation/reduction potential and pH of the surface soil in MF plots were within the normal range, indicating that these soil factors were not associated with growth inhibition observed in MF plots. Our results implied that rice cultivars with a long growing period that are able to recover from the initial growth inhibition, such as medium or late maturing cultivars, are suitable for paddy rice production fertilized with ADM.
Radionuclides were released into the environment as a consequence of the Fukushima Daiichi Nuclear Power Plant accident that occurred on 11 March 2011. Radiocesium at an abnormal concentration was detected in brown rice produced in paddy fields located in northern part of Fukushima Prefecture. We examined several hypotheses that could potentially explain the excessive radiocesium level in brown rice in some of the paddy fields, including (i) low exchangeable potassium content of the soil, (ii) low sorption sites for cesium (Cs) in the soil, and (iii) radiocesium enrichment of water that is flowing into the paddy fields from surrounding forests. The results of experiments using pots with contaminated soil indicated that the concentration of radiocesium in rice plants was decreased by applying potassium or clay minerals such as zeolite and vermiculite. The obtained results indicated that high concentrations of radiocesium in rice are potentially a result of the low exchangeable potassium and sorption sites for Cs in the soils. Application of potassium fertilizer and clay minerals should provide an effective countermeasure for reducing radiocesium uptake by plants. Radiocesium-enriched water produced by leaching contaminated leaf litter was used to irrigate rice plants in the cultivation experiments. The results indicated that the radiocesium concentrations in rice plants increased when the radiocesium-enriched water was applied to the potted rice plants. This indicated the possibility that the radiocesium levels in brown rice will increase if the nuclide is transported with water into the rice paddy fields from surrounding forests.
The vigour of seed material determines the seed’s future productivity. Although there are several tests for determining seed vigour, there is a lack of standardization for the vegetative forms of seed material, including seed potatoes. We evaluated the vigour of mother tubers of 14 selected potato (Solanum tuberosum L.) cultivars using the method of accelerated ageing, that is, tubers were placed under conditions conducive to their physiological ageing from harvest to planting, in which the most important was the appropriate temperature (18ºC). The decrease in yield caused by such treatment in relation to the optimal storage conditions is a measure of vigour. As traits of tuber ageing, we evaluated the ways in which mother tubers sprouted, the lack of emergence on the plots and yield reduction in the mother tubers subjected to conditions conducive to physiological ageing from harvest to planting. The assessment of vigour was presented on a 9-point scale for ralative yield. There were 3 cultivars that maintained high growth vigour of seed tubers while ageing in the light (mark 9) and 4 cultivars ageing in darkness (mark 8). The vigour of potato mother tubers was not correlated with either the length or mass of sprouts, or the percentage of sprouting eyes, nor was it correlated with the duration of the crop cycle of the individual cultivars. Application of this method allows potato cultivars to be characterized in the same way, regardless of the year of research and the set of cultivars being evaluated.
In the production of sugarcane, stubble shaving that cuts the residual stubble of the previous crop is carried out to promote ratoon crop growth. On the other hand, in the production of feed crops, it is generally considered that high-level cutting increases the yield of the regrowth crop. In this study, the growth and yield of the forage sugarcane subjected to high-level cutting without stubble shaving (HC) were compared with those of the plants subjected to stubble shaving (Control) to clarify the necessity of stubble shaving in the cultivation of a forage sugarcane variety, KRFo93-1. The influence of high-level cutting on the growth and yield of ratoon crop was evaluated from the first ratoon crop (RC1) to sixth ratoon crop (RC6). Tiller number in the Control plot was not different from that in the HC plots in all ratoon crops from RC1 to RC6. Stem length was significantly larger in HC than in the Control plot in all ratoon crops at the initial stage of regrowth, and in RC1, RC3, RC5 and RC6 around the harvest time. Dry matter yield was significantly higher in HC than in the Control plot in RC1, RC3, RC5, RC6 and in the sum of the ratoon crops. Although no significant difference was observed in RC2 or RC4, the dry matter yield of HC exceeded that of Control plot. The increase in the dry matter yield of HC was due to an enhancement of stem growth, since the single stem dry weight were larger in HC than in Control plot. Thus, cultivation management without stubble shaving is recommended in KRFo93-1.
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.
We previously reported two methods of phosphorus (P) supply that improve crop growth. One is to apply P-fertilizer locally into soils and the other is seed P-enrichment by soaking seeds in P-solution. Here, we examined which of the two methods or a combination of the two is more effective for wheat grown in pots. Each method increased dry matter to a similar extent but with a different time interval. The effect of localized P-application was observed at 25 d after sowing (DAS), while that of seed-P enrichment was observed at 50 DAS. Despite the positive effects of both methods, their combination had no additive effect. At 50 DAS, the growth variations were explained by P content, which depended on root length. We therefore assume that increasing root length may be the common and biologically relevant feature of both methods and that either application alone is sufficient to achieve this effect.
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