Fukuyo Tanaka

Brown spot (BS), caused by the fungal pathogen Bipolaris oryzae , is a major disease threatening global rice production. However, the genetic basis of host BS resistance remains unclear. Here, we identified brown spot resistance 1 ( bsr1 ), a quantitative trait locus conferring BS resistance, by map-based cloning. We show that bsr1 encodes a sucrose transporter and that a near-isogenic line carrying bsr1 ( bsr1 -NIL) in the susceptible Koshihikari genetic background exhibited resistance to BS by suppressing sucrose efflux into the apoplast after pathogen attack. Furthermore, bsr1 -NIL also showed strain-specific resistance to bacterial blight caused by Xanthomonas oryzae pv. oryzae through the same mechanism. These findings demonstrate that bsr1 confers dual resistance to fungal and bacterial diseases by regulating sucrose efflux. Our study identifies a previously unrecognized mechanism underlying resistance to both BS and bacterial blight and highlights bsr1 as a promising target for breeding disease-resistance rice cultivars. Rice ( Oryza sativa L.) is a staple food for more than half of the world’s population ¹ . Brown spot (BS), caused by the fungus Bipolaris oryzae , is one of the most prevalent fungal diseases of rice, and its incidence has increased under global warming ² . BS infects coleoptiles, leaves, leaf sheaths, panicle branches, glumes, and spikelets, and severe infection can substantially reduce grain yield.

Co-inoculation of soybeans with Bradyrhizobium and plant growth-promoting bacteria has displayed promise for enhancing plant growth, but concrete evidence of its impact on soybean yields is limited. Therefore, this study assessed the comparative efficacy of two 1-aminocyclopropane-1-carboxylate deaminase-producing Pseudomonas species (OFT2 and OFT5) co-inoculated with Bradyrhizobium ottawaense (SG09) on the growth, physiology, nodulation efficiency, and grain yield of three major Japanese soybean cultivars: Enrei, Fukuyutaka, and Satonohohoemi. The experiments were conducted in a warehouse under natural light conditions. The treatments included the inoculation of SG09, SG09 + OFT2, and SG09 + OFT5. Compared with Bradyrhizobium inoculation alone, co-inoculation led to significant improvements in nodulation efficiency, growth, and physiological performance in the Enrei and Fukuyutaka cultivars, but not in the Satonohohoemi cultivar. Furthermore, co-inoculation significantly boosted the total nitrogen content and ion uptake in the shoots, ultimately leading to a remarkable improvement in the grain yield in the Enrei and Fukuyutaka cultivars. These findings contribute to clarifying the interplay among Bradyrhizobium, Pseudomonas, and the plant host cultivar. Notably, Bradyrhizobium–Pseudomonas co-inoculation represents a potentially effective biofertilization strategy for soybean production, highlighting promising avenues for sustainable agricultural practices.

Owing to the worldwide shortage of nitrogen (N) fertilizers, diazotrophic endophytes have received increasing attention as biofertilizers. In this study, we investigated the inoculation effects of a diazotrophic endophyte (Bradyrhizobium sp. AT1) on three different cultivars of sweet potato (cvs. Beniazuma, Ayamurasaki, and Kokei No. 14) under pot, container, and different field conditions. Following inoculation, the root length was increased in cvs. Beniazuma and Ayamurasaki but suppressed in cv. Kokei No. 14 in pots, filled with a mixture of vermiculite, potting soil, and pearlite. AT1 inoculation also increased shoot growth in cv. Beniazuma and tuber formation in cv. Ayamurasaki in containers filled with vermiculite, potting soil, and light-colored Andosol. In field experiments, carried out at two field sites with the three cultivars, AT1 inoculation increased the growth of cvs. Beniazuma and Ayamurasaki, but it had almost no effect on cv. Kokei No. 14. In addition to growth promotion, inoculation of micropropagated sweet potato cv. Beniazuma with AT1 led to N derived from air (Ndfa) and acetylene reduction activity (ARA) five months after inoculation. Our studies indicate that AT1 inoculation can enhance the growth of sweet potato and promote N₂ fixation.

Watercore is a physiological disorder in apple (Malus × domesticaBorkh.) fruits that appears as water-soaked tissues adjacent to the vascular core, although there is little information on what exactly occurs at cell level in the watercored apples, particularly from the viewpoint of cell water relations. By combining picolitre pressure-probe electrospray-ionization mass spectrometry (picoPPESI-MS) with freezing point osmometry and vapor pressure osmometry, changes in cell water status and metabolisms were spatially assayed in the same fruit. In the watercored fruit, total soluble solid was lower in the watercore region than the normal outer parenchyma region, but there was no spatial difference in the osmotic potentials determined with freezing point osmometry. Importantly, a disagreement between the osmotic potentials determined with two methods has been observed in the watercore region, indicating the presence of significant volatile compounds in the cellular fluids collected. In the watercored fruit, cell turgor varied across flesh, and a steeper water potential gradient has been established from the normal outer parenchyma region to the watercore region, retaining the potential to transport water to the watercore region. Site-specific analysis using picoPPESI-MS revealed that together with a reduction in turgor, remarkable metabolic modifications through fermentation have occurred at the border, inducing greater production of watercore-related volatile compounds, such as alcohols and esters, compared with other regions. Because alcohols including ethanol have low reflection coefficients, it is very likely that these molecules would have rapidly penetrated membranes to accumulate in apoplast to fill. In addition to the water potential gradient detected here, this would physically contribute to the appearance with high tissue transparency and changes in colour differences. Therefore, it is concluded that these spatial changes in cell water relations are closely associated with watercore symptoms as well as with metabolic alterations.

貯蔵中食物における害虫発生の早期検出を可能にするため，揮発性のマーカー成分の利用を検討している．玄米の害虫加害マーカー候補のうち，ガイマイツヅリガとノシメマダラメイガの指標となるプレノールとイソプレノール，コクゾウムシの指標となるDMTSについて，リアルタイム質量分析計による迅速診断の可能性を検討した． プレノールとイソプレノールの検出にはNO^＋ によるイオン化によるm/z 86，DMTSにはNO^＋ イオン化によるm/z 126を選択し，SIMモードにより測定した．プレノールとイソプレノールは構造異性体のためプロダクトイオンでは識別できないが，プレノールはそのアルデヒドであるプレナールと濃度が同期することから，プレノール類とプレナール（NO^＋, m/z 83）を同時計測することでプレノールとイソプレノールの識別が可能となる．ガイマイツヅリガではプレノールがノシメマダラメイガではイソプレノールが生成したと考えられ，ガイマイツヅリガは実験開始から6日目以降に，ノシメマダラメイガでは31日目以降に卵添加なしと比べて有意な増加が認められた．DMTSでは期間を通じて低濃度で推移し，日間差と処理間差が同程度のためSIMによる診断は困難と考えられた． マーカー成分を特定しないFSモードの全データを用いた主成分分析を1，29，36日目に行った．NO^＋ によるイオン化により処理区の差異が最も明瞭で，コクゾウムシについても29日目以降に識別可能であった．今後，スケールを拡大しながら実用化に向けた詳細な検討が必要である．

Watercore is a so-called physiological disorder of apple (Malus domestica L.) that commonly occurs in several well-known cultivars. It is associated with a rapid softening of the flesh that causes a marked changed in flavor and texture. In Asia, apples with watercore are preferred and considered a delicacy because of their enhanced sweet flavor. The ‘Fuji’ cultivar, the first cultivar with rich watercore that is free from texture deterioration, has played a key role in the development of the market for desirable watercored apples. This review aimed to summarize and highlight recent studies related to the physiology of watercore in apples with special focus on ‘Fuji’ and related cultivars.

In previous work, probe electrospray ionization/mass spectrometry (PESI/MS) and sheath-flow probe electrospray ionization/mass spectrometry (sfPESI/MS) were reported for the rapid and minimally invasive analysis of food. In this work, a modified version of sfPESI will be reported. The sample surface was pricked with an acupuncture needle inserted in the sfPESI probe that protruded from the terminus of the tip by 5 mm. The invasion depth of the needle into the sample was ∽1 mm. After sampling, the needle was retracted into the solvent-preloaded capillary with a protrusion length of 0.1∽0.2 mm from the tip. A mass spectrum of sample captured on the needle was obtained by applying a high voltage to the needle. This method could be applicable to profiling analysis of plants with the epicuticular wax covering on the surfaces that are difficult to analyze by sf-PESI. The on-site mass spectrometric analysis for a growing apricot in the field was made to monitor the developing stage of the fruit.