ABSTRACTBelt-planting is a novel method for productivity of all wheat (Triticum aestivum L.) varieties, first practiced in China, in which seeds are set on a wide belt (7–12 cm in width) rather than on a conventional line swath ∼3 cm). Belt-planting allows the seeds to be uniformly distributed in the soil and increases the probability of success in establishing desirable stands, spike number per unit area and grain yield. During recent years, belt-planting has been successfully combined with other planting systems. A combination of belt-planting with precision sowing shows the integrated advantages of both technologies. Belt-planting in a strip tillage and direct drilling system has the potential to become an economically viable method for wheat productivity, facilitating the development of environmentally friendly and resource-efficient agriculture. We review the existing literature regarding the potential advantages and underlying mechanisms of belt-planting as a potential method to ensure wheat growth and productivity. We then propose future research directions related to practicing these planting methods to further improve and promote belt-planting-based technologies.

ABSTRACTNatural root grafting is a well-known phenomenon in perennial tree species. This study examined whether root grafting is possible between the same and different annual crop species without any surgical action by using an instrument with a narrow and tight rooting passage to evaluate the application of natural root grafting. A part of the epidermal cell layer disappeared and cortex tissues of two individual plants became fused together in most of species examined. When two different species were grafted, sequential images proved that whole cowpea tap root was inserted into the cortex layer of mung bean. These results indicated that natural root grafting of annual crop species without any surgical action is possible when the two growing roots come in contact with each other in a narrow and rigid rooting channel.

ABSTRACTRelationships between wheat (Triticum æstivum L.) yield components and growing season weather conditions (e.g. temperature, precipitation, and sunshine duration) were investigated for a rice-wheat rotation paddy system situated in Northern Kyushu, Japan over a 17-year period (2000–2016). A 1.0 mm increase in precipitation from 21 to 32 days after sowing decreased wheat yield by about 27 kg ha−1 at early seedling stage with one to two leaves (Zadoks (Z) growth stage Z1.1–1.2). Number of tillers and spikes showed significant negative correlations to the amount of precipitation during the period. An hour increase in mean daily sunshine hours from 94 to 111 days after sowing resulted in an 328 kg ha−1 rise in grain yield at stem elongation stage with the first and second node detection (Z3.1–3.2). The grain number per square meter also showed strong positive correlations to sunshine hours during the same period. However, this positive effect of sunshine was negated when precipitation exceeded about 30 mm during the early seedling stage. Consequently, precipitations at early seedling stage and sunshine hours at stem elongation stage mostly determined wheat yield in Northern Kyushu paddy field. Increasing precipitations during the early seedling stage highlights the pressing need for effective paddy field drainage management from wheat sowing through harvest.Abbreviations: CP: Chikushi Plains; FARC: Fukuoka prefectural Agriculture and Forestry Research Center; SARC: Saga prefectural Agricultural Research Center; DAS: days after sowing

ABSTRACTA halophyte, the common ice plant (Mesembryanthemum crystallinum L.), shows the maximal growth under salinity, in which almost all crops die. The NaCl-stimulated growth, which is referred to as halophilism, is an important trait for adaptation to salinity, but the mechanism is still unclear. To elucidate factors contributing to the halophilism, we tested the effects of NaCl on growth, ion accumulation, and expression of ion homeostasis-related genes in suspension-cultured cells. Among nine ions analyzed, Na+, Cl−, K+, and NO3− were accumulated significantly in the cells showing halophilism than that in the salt-untreated cells, and the accumulation of these ions was positively correlated with the growth. Also, the expression of ion homeostasis-related genes for plasma membrane transporters and channels for incorporation of nitrate (McNRT1), sodium (McHKT1), potassium (McKmt1), cations/Cl− (McCCC1), for tonoplast antiporters H+/Cl− (McCLC1) and Na+/H+ (McNHX1), and V-ATPase subunit c (McVmac1) for sequestration of Cl− and Na+ into the vacuole, and for enzymes catalyzing biosynthesis of proline (McP5CS) and ononitol (McImt1) was higher in the cells showing halophilism than that in the salt-untreated cells. These results indicate that the ion accumulation and the expression of ion homeostasis-related genes contribute to the NaCl-stimulated growth enhancement in the halophyte, the common ice plant.Abbreviations: CCC: cation/Cl- cotransporter; CLC: H+/Cl–antiporter; DW: dry weight; FW: fresh weight; HAK: high affinity potassium; HKT: high potassium transporter; Imt: myo-inositol O-methyl transferase; MIP: major intrinsic protein; NHX: Sodium/proton antiporter; P5CS: delta 1-pyrroline-5-carboxylate synthase; PCV: Packed cell volume; PEG: polyethylene glycol; XTH: xyloglucan endotransglucosylase/hydrolase

ABSTRACTSowing using a rotary tiller rotating in reverse (up-cut) is a labor-saving technology for soybean production because it can perform tillage and sowing, make ridges, and bury winter crop residues in one operation. However, the power requirement of up-cut rotation is higher than of normal rotation (down-cut), resulting in lower working speeds. Shallow tillage sowing methods may be a solution to this problem. Here, we develop a shallow tillage sowing method using an up-cut rotary and a side-disk which could perform the aforementioned works in one operation and conducted field experiments in 2015 and 2016 to study the effect of our sowing method (up-cut shallow tillage; UST) on ridge shape, soil volumetric water content (VWC) and soybean growth and yield, compared to conventional sowing methods (up-cut conventional tillage; UCT, and down-cut conventional tillage; DCT). Ridge shape did not differ among sowing methods. The VWC at 10 and 20 cm depths in DCT was always higher than in UST and UCT, indicating poorer drainage. The VWC at 10 cm depth decreased quickly after rain in UST and UCT, indicating good surface-layer drainage, but at 20 cm depth in UCT, VWC was lower than in UST, especially during dry spells, indicating higher water-holding capacity in UST than in UCT. Shoot and root growth and seed yield did not differ among sowing methods, indicating that UST did not negatively affect soybean growth and yield. These results suggest that UST can be used for soybean production.

ABSTRACTAtmospheric carbon dioxide (CO2) is predicted to reach 550 µmol mol−1 by 2050, increasing from the current ~410 µmol mol−1 concentration, and this will have an impact on wheat production and grain quality. Genetic differences in response to future CO2 levels, which might be exploited for higher yield and sustainable grain quality, were investigated. Twelve diverse genotypes (11 wheat lines and 1 triticale cultivar) were grown in the Australian Grains Free-Air CO2 Enrichment facility under ambient CO2 (~400 µmol mol−1) and elevated CO2 (eCO2) concentrations (550 µmol mol−1) in 2014 and 2015 to test for different responses to CO2. Genotype response to eCO2 for the parameters measured showed strong linear relationships. eCO2 increased plant height (11%), aboveground biomass (31%) and grain yield (32%) as means across all genotypes. Yield response to eCO2 was driven by increases in spike number and weight. The increase in CO2 caused a mean 10% decrease in grain nitrogen content and increased grain weight by 7%. Measures of bread dough quality decreased due to eCO2. Genotypes with large yield response did not show larger than mean reductions in grain %N. The apparent near-universal decline in grain %N under eCO2 might be compensated for by selection of genotypes that are highly responsive to increasing yields but resist dramatic declines in grain %N. Selection for responsiveness to eCO2 for yield and grain %N are likely to involve a range of co-related characteristics that balance sink and source relationships.

ABSTRACTWe conducted a quantitative trait locus (QTL) analysis of grain appearance (GA) and agronomic traits of rice, using 128 recombinant inbred lines derived from ‘Emi-no-kizuna’ and ‘Tomohonami’. We detected two promising QTLs associated with GA: qGA4 on chromosome 4 and qGA8 on chromosome 8. qGA4 contributed highly to the greater percentage of perfect grains of the Emi-no-kizuna genotype. In the same region, we detected other QTLs associated with panicle number and spikelet number per panicle. In near-isogenic lines (NILs) in which Emi-no-kizuna alleles were introgressed in the genomic region of only the semi-dwarf 1 (sd1) locus (NIL_1) and both the sd1 locus and qGA8 (NIL_2), respectively, the percentage of perfect grains was significantly higher and the percentages of milky white, basal white, and white back grains were significantly lower than in Tomohonami; and the percentages of milky white and white back grains of NIL_2 were significantly lower than those of NIL_1. These results suggest that introgression in the sd1 region could improve GA, and that the addition of qGA8 could further improve GA. The culm lengths of the NILs were significantly shorter than that of Tomohonami, indicating improved lodging resistance. Grain weight of NIL_2 was significantly smaller than that of NIL_1, suggesting that the effect of qGA8 could be pleiotropic, or the gene that underlies qGA8 could be linked with genes associated with grain weight.Abbreviations: ANOVA: analysis of variance; AT20: mean air temperature in the 20 days after heading; BW: basal white grain; CL: culm length; DAH: days after heading; GA: grain appearance; GW: 1000-grain weight; LOD: logarithm of odds; MW: milky white grain; NIL: near-isogenic line; PG: perfect grain; PL: panicle length; PN: panicle number; PTSN: putative total spikelet number; PVE: percentage of phenotypic variation explained; QTL: quantitative trait locus; RIL: recombinant inbred line; SN: spikelet number per panicle; SNP: single nucleotide polymorphism; WB: white back grain

ABSTRACTIn sub-Saharan Africa (SSA), rice production from smallholder farms is challenged because of a lack of fertilizer inputs and nutrient-poor soils. Therefore, improving nutrient efficiency is particularly important for increasing both fertilizer use and rice yield. This review discusses how to improve the return from fertilizer input in terms of agronomic N use efficiency (AEN), that is, the increase in grain yield per kg of applied N, for rice production in SSA. The AEN values we summarized here revealed large spatial variations even within small areas and a certain gap between researcher-led trials and smallholder-managed farms. Experimental results suggest AEN can be improved by addressing spatial variations in soil-related factors such as P, S, Zn, and Si deficiencies and Fe toxicity in both irrigated and rainfed production systems. In rainfed production systems, differences in small-scale topography are also important which affects AEN through dynamic changes in hydrology and variations in the contents of soil organic carbon and clay. Although empirical evidence is further needed regarding the relationship between soil properties and responses to fertilizer inputs, recent agricultural advances have generated opportunities for integrating these micro-topographical and soil-related variables into field-specific fertilizer management. These opportunities include UAV (unmanned aerial vehicle) technology to capture microtopography at low cost, database on soil nutrient characteristics at high resolution and more numbers of fertilizer blending facilities across SSA, and interactive decision support tools by use of smartphones on site. Small-dose nursery fertilization can be also alternative approach for improving AEN in adverse field conditions in SSA.ABBREVIATIONS: AEN: agronomic nitrogen use efficiency; FISP: farm input subsidy program; VCR: value cost ratio; SOC: soil organic carbon; SSA: sub-Saharan Africa; UAV: unmanned aerial vehicle

ABSTRACTOil pollution is a worldwide threat to the environment that affects the development of plants. The effect of soil contaminated by diesel on the physiological responses of seedlings of Quercus oleoides was investigated in two independent experiments. We proposed that physiological performance will decrease when seedlings are exposed to higher concentration of contamination. At the first experiment, levels of pollution with diesel were of 0%, 5%, 10% and 15%, and 0%, 2% and 3.5% in the second one. In the first experiment, photosynthetic rate, stomatal conductance, transpiration and total chlorophyll of Q. oleoides were higher in the control seedling, and lower in treatments of pollution with 5%, 10% and 15% of diesel during 3 days of treatment. Only, seedlings in soil polluted with 5% of diesel survived up to 16 days; they showed a photosynthetic rate of 5 μmol m−2 s−1, which was lower than control seedlings (9 μmol m−2 s−1). This pattern was observed in stomatal conductance, transpiration and relative water content. Surprisingly, in the second experiment, seedlings showed a higher photosynthetic rate and growth at 2% of diesel-contaminated soil than control seedlings, a phenomenon known as hormesis. In both experiments, soil respiration was proportional to soils contaminated. We concluded that Q. oleoides is highly vulnerable in soils contaminated with above 5% of diesel, but it maintains its physiological activities in soils contaminated below 2%, suggesting that seedlings can grow under low concentration of diesel contaminant, and may be used in phytoremediation of soils with low concentrations of diesel contamination.

ABSTRACT Root growth into hypoxic or anoxic waterlogged soil relies on internal aeration in plants. The plant hormone ethylene helps adapt to waterlogging by inducing the formation of aerenchyma, which provides a low-resistance pathway for the transport of oxygen from the shoot to the root apex. Waterlogging-susceptible crops including barley start to form aerenchyma after suffering waterlogging stress. But waterlogging can be fatal if aerenchyma formation is not fast enough. Here, we investigated whether pre-treating barley with ethephon, an ethylene-releasing agrochemical, could improve its tolerance to mimicked waterlogging conditions (using stagnant deoxygenated agar nutrient solution). In barley growing in aerated nutrient solution, ethephon treatment enhanced aerenchyma formation at the root tips and induced the development of shorter and shallower roots. Pre-treating barley leaves also delayed waterlogging-caused whiting and increased the percentages of viable root-tips under waterlogging conditions. However, the pretreatment did not noticeably increase fresh weight or shoot length. Further studies are needed to optimize ethephon treatment conditions to improve barley production under waterlogged conditions.