Organic Acid Effects on Nutrient Uptake by Rice

The purpose of this work was to evaluate the responses of 20 rice cultivars to the phytotoxic effects of acetic, propionic, and butyric acids produced in soils under anaerobic conditions. The study was conducted in a hydroponic system, with four levels (0, 3, 6, and 9 mM) of the three organic acids in the ratio of 6:3:1 in a factorial of complete randomized block design with three replications. The evaluated variables were phosphorus (P) and potassium (K) contents. The analysis of variance revealed a significant interaction, and the established regressions showed differences among the genotypes as evaluated for both variables. Four genotypes were classified as tolerant in relation to P content and three genotypes as tolerant in relation to K. The best performance was verified with japonica genotypes and the irrigation-based growing system.     

不同生育期水稻干物质量与产量的关系研究

为明确不同生育期的干物重对粤晶丝苗2号、粤农丝苗、合美占3个水稻(Oryza sativa L.)品种的产量及产量构成因素的影响,设置了早造和晚造两次不同氮肥梯度随机区组栽培试验。结果表明,叶片干物质的分配比例在拔节孕穗期时最高,且其随着生育进程逐渐降低,在乳熟期达到最低值;茎干物质的分配比例在乳熟期降至最低;齐穗期的穗干物质分配比例不到20%,而乳熟期的穗干物质量将近占总干物质量的43%;早造和晚造水稻的结实率差异极显著,总干重差异显著,而穗数、每穗粒数、千粒重、产量差异不显著;齐穗期以后,结实率和千粒重均与干物重呈负相关,而叶干重与穗数呈显著正相关,且相关性较大,茎干重与各产量性状密切相关,总干重与产量呈正相关。水稻干物重是决定高产的重要因素。     

施钾对青引1号燕麦草产量及根系的影响

在缺钾地区，开展了不同施钾对青引1号燕麦（Avena sativa cv. Qingyin No.1）干物质产量和根系的影响，找出最佳施钾量，为青海省燕麦种子生产提供依据。结果表明，在施N 54.75 kg/hm2和施P2O5 51.75 kg/hm2的基础上，施K2O 40 kg/hm2，青引1号燕麦开花期收获时可获得最高的干物质产量和蛋白产量，分别为29575.0和2099.8 kg/hm2，二者均符合Y=a+bK+cK2函数变化。施K2O 40 kg/hm2，青引1号燕麦株高、总分蘖数、根长和根数最大，分别为184.5 cm、3.22个/株、15.90 cm和26.17 条/株； 施K2O 20 kg/hm2时，植株茎粗和根量达最大，分别为0.585 cm和0.540 g/株。各产量性状、地下生物量以及饲草和蛋白产量间均存在显著或极显著正相关关系。     

EFFECTS OF pH ON GROWTH AND NODULATION OF TWO FORAGE LEGUMES

A study was conducted to compare the responses to acid pH of Medicago sativa and Lotus glaber, two forage legumes with different environmental requirements, either supplied with inorganic nitrogen (N) or inoculated with different strains of their nodule bacteria. Medicago sativa showed, in both treatments, a significant reduction in total dry weight at pH below 6.0. In contrast, Lotus glaber grew equally well at all the pHs assayed in the presence of adequate N. Under inoculated conditions, in the absence of N supply, plant growth was dependent on the bacterial strain used. When the ability of each strain to multiply in culture medium was examined, it was observed that Sinorhizobium meliloti strains showed a pH-sensitive response that inhibited growth at pH 4.0, whereas Mesorhizobium loti strains showed normal growth at this pH. These results suggest that for the effectiveness of Mesorhizobium loti–Lotus glaber symbiosis in acid soils the major factor to be considered is the tolerance of the bacterial strain to acid conditions, while the limiting factors for the Sinorhizobium meliloti–Medicago sativa symbiosis are the sensitivity to low pH of both the plant and its bacteria.     

Developmental Dynamics and Early Growth Vigour in Rice. I. Relationship Between Development Rate (1/Phyllochron) and Growth

Achieving early vigour, that is, rapid dry matter accumulation, is a priority in rice crop improvement, but this trait is complex and not well understood genetically and physiologically. This study tested the hypothesis that the development rate (DR) contributes to early vigour. Two diversity panels were phenotyped during vegetative stage for traits constituting early vigour (shoot dry weight, SDW; relative growth rate, RGR) or contributing to early vigour (tillering, leaf size, DR). The first panel comprised 169 genotypes from all major genetic groups of Oryza sativa and was phenotyped under irrigated upland conditions in the field (Philippines, Exp1). The second panel with 190 genotypes representing the diversity of the tropical japonica group was phenotyped in pots in a greenhouse (Montpellier, France, Exp2). Results from field and pot experiment pointed out that DR, tillering and leaf size were positively correlated with RGR and SDW, although the contribution of leaf size was small. DR was positively correlated with tillering but both were negatively correlated with leaf size. DR vs. RGR correlation was conserved in subsets of genotypes with similar leaf size and tillering, suggesting an effect of DR on RGR independent of the other traits. DR is a promising, still underexploited trait contributing to rice early vigour, requiring further genetic and physiological characterization.     

杂草稻对粳稻生长及产量的影响

在同期播种情况下,和粳稻相比,杂草稻出苗时的叶片更肥长、营养生长期的植株更高、分蘖数多达4倍以上。不同生物型杂草稻的落粒性差异较大。杂草稻密度愈高对栽培粳稻的产量影响愈大。     

干尖线虫病对不同水稻品种（系）产量相关性状的影响

[目的]该研究旨在了解干尖线虫病对不同水稻品种的影响。[方法]通过田间表型观察与室内考种试验，对自然发病状态下的4个常规粳稻品种（系）和粳稻恢复系 R161进行了观察和分析。[结果]不同水稻品种（系）被侵染后的症状存在差异，常规粳稻宁1707、宁1818、镇稻88和南粳9108被侵染后表现"干尖"和"小穗头"症状，粳稻恢复系R161只表现"干尖"，不表现"小穗头"症状，且"干尖"的位置不同，分别位于剑叶叶尖，整片剑叶及倒二叶。供试材料被水稻干尖线虫侵染后均能抽穗，但是株高、穗长、结实率和千粒重均受到不同程度的影响。此外，R161被干尖线虫侵染后，不同发病部位对水稻产量的影响不同，整片剑叶干枯扭曲的稻穗受影响最大。[结论]该研究为进一步阐明我国水稻干尖线虫病的危害规律和制定相应的防治措施提供依据。     

蚕豆黄化卷叶病的药剂防治

喷药治蚜防病试验中,溴氰菊酯和久效磷对豆蚜(Aphis craccivora)的防效分别达到96.7%和67.1%。两次和三次施用溴氰菊酯的防病效果分别达到84.1%和86.1%,蚕豆产量分别比未施药对照增产17.7%和21.9%。施药也影响蚕豆黄化卷叶病的时间分布型,三次施药小区的病株始终为泊松分布,病害没有再次扩散;未施药小区早春病株就出现负二项分布,越冬前病害已经扩散。豆蚜蚜害率与蚕豆黄化卷叶病发病率密切相关。     

Effectiveness of Coniothyrium minitans and Trichoderma atroviride in suppression of sclerotinia blossom blight of alfalfa

The effects of the mycoparasites Coniothyrium minitans and Trichoderma atroviride on the suppression of alfalfa blossom blight caused by Sclerotinia sclerotiorum were evaluated under indoor and field conditions. When T. atroviride (9·0 × 10⁴ conidia/floret) + S. sclerotiorum (6·0 × 10³ ascospores/floret) or C. minitans (9·0 × 10⁴ conidia/floret) + S. sclerotiorum (6·0 × 10³ ascospores/floret) were applied to detached young alfalfa florets, T. atroviride effectively inhibited saprophytic growth of S. sclerotiorum, whereas C. minitans showed no inhibition under the same conditions. When T. atroviride (6·9 × 10⁴ conidia/floret) + S. sclerotiorum (6·0 × 10³ ascospores/floret) or C. minitans (6·9 × 10⁴ conidia/floret) + S. sclerotiorum (6·0 × 10³ ascospores/floret) was applied to young alfalfa petals in vivo just after pollination, the percentage of pod formation was higher for T. atroviride+S. sclerotiorum than that for C. minitans+S. sclerotiorum, and the percentage of pod rot was lower for T. atroviride+S. sclerotiorum than that for C. minitans+S. sclerotiorum. However, when they were applied to senescent petals attached to developing pods of alfalfa at 9·2 × 10⁴ conidia/floret together with S. sclerotiorum at 4·5 × 10³ ascospores/floret at 14 days after pollination, C. minitans was more effective than T. atroviride in suppressing sclerotinia pod rot and seed rot of alfalfa. Field experiments showed that three applications of C. minitans (5·4 × 10⁶ conidia mL⁻¹) or T. atroviride (5·4 × 10⁶ conidia mL⁻¹) at a 7-day interval to blossoms of alfalfa effectively suppressed sclerotinia pod rot in two out of three annual trials. Coniothyrium minitans effectively suppressed sclerotinia seed rot in all three years, whereas T. atroviride was not effective against seed rot in any of the trial years. The efficacy of C. minitans was not significantly different (P > 0·05) from benomyl (250 µg ai mL⁻¹). This study suggests that C. minitans has potential as a biocontrol agent to control blossom blight of alfalfa caused by S. sclerotiorum.     

Inhibitory and promotive allelopathy in rice (Oryza sativa L.)

Studies on allelopathic rice, which inhibits the germination and development of weeds such as barnyardgrass ( Echinochloa spp.) and ducksalad [ Heteranthera limosa (Sw.) Wild.], have been strongly conducted in the USA, the Philippines, Japan, Korea, and other countries since the 1980s. Weed-suppressing rice plants can compete with weeds for light and mineral nutrients by their rapid and thick growth characteristics, and probably also by their allelopathic effects. It was suggested that allelopathic properties were inherited from parents. Different screening methods for finding allelopathic rice simply and rapidly have been proposed. In contrast, stimulative allelopathy in rice, which promotes germination of the dormant and dormancy-awakened seeds of Monochoria vaginalis (Burm. f.) Kunth var. vaginalis , has been investigated by the authors since the 1990s. Rice seeds promoted the germination in the dark and in light under submerged conditions. Our experiments suggested that rice seeds, hulls, plants and straw contain stimulative substance(s) that promote seed germination of M. vaginalis .