基于卷积神经网络的列当种子发芽识别方法

列当是一种极具破坏力的寄生性杂草,目前难以用常规方法根除。通过使用发芽刺激物可以诱导列当“自杀性萌发”,因此识别特定发芽刺激物下的种子发芽率至关重要。针对显微镜下人眼视觉对列当种子发芽判断标准不统一和耗时耗力等问题,本研究提出一种基于卷积神经网络的列当种子发芽识别算法。首先,培育列当种子并采用显微镜采集发芽和未发芽的种子构建列当图像库;然后,通过搭建卷积神经网络来提取列当图像的特征实现种子发芽识别,通过试验对比优化超参数,得到适合列当种子识别的OB-Net模型;最后,通过试验图像验证,本研究模型可达到95.2%的识别准确率;与现有主流网络模型进行对比证明了构建的OB-Net模型在列当种子识别方面具有最高的精度和较快检测速度。本研究的列当种子发芽识别方法可以为相关发芽刺激物的研究提供有效的理论支撑。

降解玉米秸秆真菌复合菌系的构建及其降解效果评价

【目的】秸秆的木质纤维素含量丰富、结构复杂,在自然界中降解较慢,增加秸秆降解菌剂中菌株的多样性有利于提升还田秸秆的降解效果。探究菌株多样性水平和组成影响复合菌系秸秆降解的效果及原因,为复合菌系在秸秆降解中的应用提供理论支撑。【方法】通过富集驯化培养,从玉米秸秆还田土壤中筛选具有秸秆降解能力的真菌,从中挑选5株高效秸秆降解真菌进行基因间隔区序列(ITS)测定和物种鉴定,明确其分类地位。通过全组合构建菌株多样性为1~5的复合菌系,分别检测复合菌系的秸秆相对降解率及其滤纸酶、纤维素内切酶和木聚糖酶活性,利用方差分析和相关性分析等方法研究菌株多样性和组成对复合菌系玉米秸秆降解效果及其纤维素酶活性的影响。【结果】共筛选获得了15株具有秸秆降解能力的真菌,其中5株真菌的秸秆降解效果好、纤维素水解能力强。经ITS序列鉴定和系统发育分析,发现5株降解真菌的遗传差异较大,Z7-6、F7-5、F4-3、L1-1和J2-5分别与草酸青霉(Z7-6:Penicillium oxalicum)、烟曲霉(F7-5:Aspergillus fumigatus)、哈茨木霉(F4-3:Trichoderma harzianum)、白囊耙齿菌(L1-1:Irpex lacteus)和木贼镰刀菌(J2-5:Fusarium equiseti)的ITS序列相似度均超过99.95%。全组合复配结果表明,复合菌系的秸秆降解能力和纤维素酶活力均高于各单一菌株,且随着菌株多样性水平的增加而提高。滤纸酶、纤维素内切酶和木聚糖酶的活力越强,复合菌系对玉米秸秆的降解效果越好,而其秸秆相对降解率主要取决于滤纸酶和纤维素内切酶的活性。抽样效应分析发现,不同菌株对复合菌系的秸秆降解效果、滤纸酶和纤维素内切酶活性的影响不同。不含菌株F7-5的复合菌系降解效果显著优于含有该菌株的组合,以Z7-6(P.oxalicum)、F4-3(T.harzianum)、L1-1(I.lacteus)和J2-5(F.equiseti)组合F1的玉米秸秆降解效果最佳、酶活性最高。【结论】秸秆降解复合菌系的构建过程需要同时考虑多样性效应和抽样效应,增加降解菌的多样性有助于增强秸秆的降解效果。本研究筛选获得的复合菌系F1在玉米秸秆降解中具有潜在的应用前景。

不同施肥制度对南方旱地红壤微生物组结构和功能影响研究进展

土壤微生物组在促进土壤养分循环、提高土壤固碳能力和维持土壤肥力等方面具有重要的作用。红壤是我国南方重要的耕地资源,但其有机质含量低、水土流失严重,且面临着土壤酸化导致的活性铁铝增加、作物生长受限和微生物活性下降等严峻问题。我国近年来基于红壤旱地长期定位试验和短期培育试验开展了很多工作,在通过调控红壤微生物组以缓解土壤酸化、增加有机质含量和提高氮磷养分有效性方面取得了突破性进展。本文综述了红壤区农田土壤微生物组结构的主要驱动因素,回顾和比较了长期施用化肥、有机肥和有机无机配施等不同施肥制度对我国南方旱地红壤微生物组结构和功能影响的研究工作,阐述了有机培肥制度对红壤微生物群落多样性的积极效应;总结了配施有机肥在提高红壤有机碳周转功能类群和氮磷代谢功能类群丰度,促进红壤有机碳分解、维持有机质稳定和提高土壤氮磷养分有效性等方面的重要作用;探讨了高多样性微生物群落中关键特殊性代谢功能对驱动微生物群落装配和维持土壤生态功能稳定的作用。最后,对我国旱地红壤微生物组未来的研究方向进行了展望,强调了可以通过改进微生物培养策略、明确微生物组不同类群的功能特征和驱动因素、充分挖掘农业微生物组资源、开发调控红壤微生物组的微生物肥料产品和高效农业管理措施来提高红壤养分循环效率、促进有机质稳定和降低铁铝活性,充分发挥微生物组在红壤耕地资源可持续利用与农业绿色发展中的作用。

Root Physiological and Morphological Characteristics of Two Rice Cultivars with Different Nitrogen-Use Efficiency

The variation in nitrogen （N） uptake by rice has been widely studied but differences in rice root morphology that may contribute to this variation are not completely understood. Field and greenhouse experiments were carried out to study N accumulation, root dry weights, total root lengths, root surface areas, and root bleeding rates of two rice cultivars, Elio with low N-use efficiency and Nanguang with high N-use efficiency. Low （1 mmol N L^-1） and high （5 mmol N L^-1） N applications were established in the greenhouse experiment, and the N rates were 0, 120, and 240 kg ha^-1 in the field experiments at Jiangning and Jiangpu farms, Nanjing, China. The results showed that the N accumulation, root dry weight, total root length, and root surface area increased with an increase in N application. At the heading stage, N accumulation in the shoots and roots of Nanguang was greater than that of Elio in the field experiments and that of Elio at 5 mmol N L^-1 in the greenhouse experiment. After the heading stage, N accumulation was higher for Nanguang at both 1 and 5 mmol N L^-1 in the greenhouse experiment. The total root length and root surface area were significantly different between the two cultivars. Over the range of the fertilizer application rates, the root lengths of Nanguang at Jiangning Farm were 49%-6170 greater at booting and 26%-39% greater at heading than those of Elio, and at Jiangpu Farm they were 22%-42% and 26%-38% greater, respectively. Nanguang had a greater root bleeding rate than Elio. It was concluded that the N-use efficiency of the two rice cultivars studied depended to a great extent on the root morphological parameters and root physiological characteristics at different growth stages.

Effect of N Fertilizers on Root Growth and Endogenous Hormones in Strawberry

Endogenous hormones play an important role in the growth and development of roots. The objective of this research was to study the effect of four types of N fertilizers on the root growth of strawberry (Fragaria ananassa Duchesne) and the endogenous enzymes of indole-3-acetic acid (IAA), abscisic acid (ABA), and isopentenyl adenosine (iPA) in its roots and leaves using enzyme-linked immunosorbent assay. Application of all types of N fertilizers significantly depressed (P ≤ 0.05) root growth at 20 d after transplanting. Application of organic-inorganic fertilizer (OIF) as basal fertilizer had a significant negative effect (P ≤ 0.05) on root growth. The application of OIF and urea lowered the lateral root frequency in strawberry plants at 60 d (P ≤ 0.05) compared with the application of two organic fertilizers (OFA and OFB) and the control (CK). With the fertilizer treatments, there were the same concentrations of IAA and ABA in both roots and leaves at the initial growth stage (20 d), lower levels of IAA and ABA at the later stage (60 d), and higher iPA levels at all seedling stages as compared to those of CK. Thus, changes in the concentrations of endogenous phytohormones in strawberry plants could be responsible for the morphological changes of roots due to fertilization.

硝态氮抑制尖孢镰刀菌侵染促进黄瓜生长的内在生理机制

【目的】连作障碍严重影响设施农业的发展。不同形态氮素可影响黄瓜土传枯萎病的发生,然而其内在生理机制尚不明确。通过氮素营养调控植物–微生物互作关系,为防控土传病害的发生提供理论依据。【方法】以黄瓜品种津春2号和尖孢镰刀菌黄瓜专化型菌(FOC)为试材,进行温室营养液培养试验。设营养液中添加铵态氮不接菌(A)、硝态氮不接菌(N)、铵态氮接菌(AI)和硝态氮接菌(NI)共4个处理。尖孢镰刀菌侵染8天后进行植株样品的采集及测定,包括株高、根长、生物量、病情指数、叶绿素含量、光合特性、叶片温度,并进行了叶肉细胞超微结构的观察,测定了植物全氮、可溶性蛋白及可溶性糖含量。【结果】与铵态氮相比,硝态氮营养显著抑制了黄瓜植株枯萎病的发病率,并显著促进了植株的生长以及植株生物量的增加。未接菌条件下,供应铵态氮的植株光合速率、气孔导度、蒸腾速率、羧化效率及表观量子效率均显著高于供应硝态氮的植株;尖孢镰刀菌的侵染导致供应铵态氮的植株叶绿体结构受损,显著降低了其光合速率、气孔导度、蒸腾速率、细胞间隙CO2浓度、羧化效率及表观量子效率,而病原菌侵染对供应硝态氮的植株叶片光合特性无显著影响。未接菌条件下,供应铵态氮的植株叶片温度及水分利用效率显著低于供应硝态氮的植株;尖孢镰刀菌侵染后,供应铵态氮的植株叶片温度及水分利用率显著增加,而病原菌侵染对供应硝态氮的植株无显著影响。叶片温度与蒸腾速率呈显著负相关关系,而与水分利用率呈显著正相关关系。供应铵态氮的植株根系全氮、可溶性蛋白及可溶性糖含量均显著高于供应硝态氮的植株,从而促进病原菌对供应铵态氮的植株的侵染。尖孢镰刀菌侵染后,供应铵态氮的植株根系可溶性蛋白含量显著增加,可溶性糖含量降低,而尖孢镰刀菌侵染对供应硝态氮的植株可溶性蛋白及可溶性糖含量无显著影响。【结论】硝态氮能够有效地抑制黄瓜枯萎病的发生,维持叶绿体结构的完整性,保持黄瓜植株正常的光合作用及生长,并减少碳水化合物向根系的运输,从而抑制病原菌的侵染及病害的发生。在黄瓜的设施栽培中,可适当增加硝态氮肥的施用而减少铵态氮肥的投入,以抑制土传枯萎病发生。

Spore production in the solid-state fermentation of stevia residue by Trichoderma guizhouense and its effects on corn growth

Trichoderma is an important and widely used plant growth-promoting fungus(PGPF).In this study,stevia residue amended with amino acids hydrolyzed from animal carcasses was used for the production of Trichoderma guizhouense NJAU 4742 by solid-state fermentation,and then its potential to promote corn plant growth was evaluated in combination with chemical fertilizer(CF)or organic fertilizer(OF).The highest spore number of 7×10^(9) CFU g^(–1) fresh weight was obtained under the following optimal parameters:material ratio of 50%(stevia residue:rice bran=1:1),pH value of 3.0(amended with 6.67%amino acids),initial moisture content of 60%,inoculum size of 10%,material thickness of 3 cm and an incubation time of 4 days.The aboveground corn plant biomass obtained with T.guizhouense applied alone and with CF treatments were slightly higher than those of no fertilizer control and CF treatments,respectively.However,T.guizhouense applied with OF significantly(P<0.05)increased aboveground biomass compared to OF and yielded the highest aboveground biomass among all the treatments.Moreover,T.guizhouense applications primarily influenced the fungal bulk soil community composition,among which three OTUs(OTU_(2) and OTU_(9) classified as Chaetomium,and OTU_(4)classified as Trichoderma)were stimulated in both bulk and rhizosphere soil.Notably,a specific OTU_(3)(Phymatotrichopsis)was only stimulated by T.guizhouense applied with OF,possibly leading to high soil productivity.These results show that it is feasible to employ stevia residue in the eco-friendly fermentation of T.guizhouense,which is strongly suggested for enhancing OF applications.

番茄育苗基质中保水剂和黏结剂的筛选及其组合效果评价

育苗基质是工厂化育苗的关键。探究添加不同保水剂及黏结剂对基质性质及幼苗生长的影响,可以为保障育苗质量并降低生产成本提供参考。选择基石抗旱(JS)、生金沙(SJS)、正能量(NL)、日本触媒(JK)4种保水剂以及凹凸棒石(AT1、AT2)和膨润土(BT1和BT2)4种黏结剂,测定它们对基质保水节水能力、黏结性及幼苗生长的影响,筛选出最优保水剂和黏结剂,进一步通过番茄育苗试验筛选出最佳的保水剂和黏结剂复配组合和适宜用量。结果表明保水剂JS的反复吸水能力最强,综合保水性能较佳。使用黏结剂AT1塞子苗形成率大于88.00%。综合塞子苗形成率及幼苗生长,黏结剂AT1效果最佳。将筛选获得的JS和AT1复配后加入育苗基质中,0.2%JS+4%AT1处理幼苗的萎蔫率相对较低,且在幼苗株高、茎粗、根长、叶面积、总干质量以及壮苗指数等生长特性及生理指标上均优于其他处理。说明0.2%基石抗旱与4%凹凸棒石1复配后添加到基质中效果最好,可以作为兼具保水节水和黏结成坨功效的番茄功能性育苗基质的推荐配方。

Enzyme Activity in Water-Stable Soil Aggregates as Affected by Long-Term Application of Organic Manure and Chemical Fertiliser

The activities of invertase, protease, urease, acid phosphomonoesterase, dehydrogenase, and catalase in different fractions of waterstable aggregates (WSA) were examined in long-term (26 years) fertilised soils. The long-term application of organic manure (OM) with chemical fertiliser (CF) significantly increased macroaggregate and decreased microaggregate percentages, enhanced the mean weight diameter, and significantly increased soil total carbon (TC) and total nitrogen (TN) contents of WSA in different size fractions. Combined fertilisation with OM and CF also increased invertase, protease, urease, acid phosphomonoesterase, dehydrogenase, and catalase activities of WSA in different size fractions. Enzyme activities were higher in macroaggregates than in microaggregates. The distribution of enzyme activities generally followed the distribution of TC and TN in WSA. The geometric mean of the enzyme activities in different WSA of OM-treated soils was significantly higher than that in soils treated with 100% CF or no fertiliser. The results indicated that the long-term combined application of OM with CF increased the aggregate stability and enzyme activity of different WSA sizes, and consequently, improved soil physical structure and increased soil microbial activity.

Suppression of Fusarium Wilt of Banana with Application of Bio-Organic Fertilizers

Fusarium wilt is one of the most serious diseases of banana plants caused by soil-borne pathogen Fusarium oxysporum f.sp. cubense(FOC). In this study a pot experiment was conducted to evaluate the effects of different bio-organic fertilizers(BIOs) on Fusarium wilt of banana, including the investigations of disease incidence, chitinase and β-1,3-glucanase activities of banana plants, and FOC populations as well as soil rhizosphere microbial community. Five fertilization treatments were considered, including chemical fertilizer containing the same N, P and K concentrations as the BIO(control), and matured compost mixed with antagonists Paenibacillus polymyxa SQR-21 and Trichoderma harzianum T37(BIO1), Bacillus amyloliquefaciens N6(BIO2), Bacillus subtilis N11(BIO3), and the combination of N6 and N11(BIO4). The results indicated that the application of BIOs significantly decreased the incidence rate of Fusarium wilt by up to 80% compared with the control. BIOs also significantly promoted plant growth, and increased chitinase andβ-1,3-glucanase activities by 55%–65% and 17.3%–120.1%, respectively, in the banana roots. The population of FOC in the rhizosphere soil was decreased significantly to about 104 colony forming units g-1with treatment of BIOs. Serial dilution plating and denaturing gradient gel electrophoresis analysis revealed that the application of BIOs increased the densities of bacteria and actinomycetes but decreased the number of fungi in the rhizosphere soil. In general, the application of BIOs revealed a great potential for the control of Fusarium wilt disease of banana plants.

Bacillus cereus X5 Enhanced Bio-Organic Fertilizers Effectively Control Root-Knot Nematodes(Meloidogyne sp.)

The efficacy of Bacillus cereus X5 as a potential biological control agent against root-knot nematodes was evaluated in vitro by examining second-stage juvenile mortality and egg hatching rate under addition of culture filtrate and in planta by application of bio-organic fertilizers enhanced with B. cereus X5, B. thuringiensis BTG, or Trichoderma harzianum SQR-T037 alone or together in greenhouse and field experiments. The biofumigation of the root-knot nematode-infested soil with organic materials (chicken manure, pig manure and rice straw) alone or in combination with B. cereus X5 was also conducted in greenhouse experiments. In laboratory, the filtrate of B. cereus X5 more effectively reduced egg hatching rates during the incubation period for 14 d and more effectively killed the second-stage juvenile during the incubation period of 24 h than that of B. thuringiensis BTG. The highest dry shoot weights for greenhouse tomatoes and field muskmelons were found in both the treatment consisting of the bio-organic fertilizer enhanced with the three biocontrol agents and the treatment consisting of the bio-organic fertilizer enhanced only with B. cereus X5. The two bio-organic fertilizers achieved better nematicidal effects than those enhanced only with B. thuringiensis BTG or T. harzianum SQR-T037. B. cereus X5 also enhanced effect of biofumigation, which resulted in increased plant biomass and reduced nematode counts in the roots and rhizosphere soil. Therefore, these results suggested that biological control of root-knot nematodes both in greenhouses and fields could be effectively achieved by using B. cereus X5 and agricultural wastes.

Effect of Nitrogen Starvation on the Responses of Two Rice Cultivars to Nitrate Uptake and Utilization

Ammonium(NH+4) is the main nitrogen(N) form for rice crops, while NH+4near the root surface can be oxidized to nitrate(NO-3)by NH+4-oxidizing bacteria. Nitrate can be accumulated within rice tissues and reused when N supply is insufficient. We compared the remobilization of NO-3stored in the tissue and vacuolar between two rice(Oryza sativa L.) cultivars, Yangdao 6(YD6, indica)with a high N use efficiency(NUE) and Wuyujing 3(WYJ3, japonica) with a low NUE and measured the uptake of NO-3, expression of nitrate reductase(NR), NO-3transporter genes(NRTs), and NR activity after 4 d of N starvation following 7-d cultivation in a solution containing 2.86 mmol L-1NO-3. The results showed that both tissue NO-3concentration and vacuolar NO-3activity were higher in YD6 than WYJ3 under N starvation. YD6 showed a 2- to 3-fold higher expression of OsNRT2.1 in roots on the 1st and 4th day of N starvation and had significantly higher values of NO-3uptake(maximum uptake velocity, Vmax) than the cultivar WYJ3.Furthermore, YD6 had significantly higher leaf and root maximum NR activity(NRAmax) and actual NR activity(NRAact) as well as stronger root expression of the two NR genes after the 1st day of N starvation. There were no significant differences in NRAmax and NRAact between the two rice cultivars on the 4th day of N starvation. The results suggested that YD6 had stronger NRA under N starvation, which might result in better NO-3re-utilization from the vacuole, and higher capacity for NO-3uptake and use, potentially explaining the higher NUE of YD6 compared with WYJ3.

Dynamic Regulation of Nitrogen and Organic Acid Metabolism of Cherry Tomato Fruit as Affected by Different Nitrogen Forms

Cherry tomatoes （Lycopersicon esculentura Mill., cv. hongyangli） were hydroponically cultivated in a greenhouse to determine the effect of different nitrogen （N） forms on organic acid concentration and the activities of related enzymes involved in nitrogen and organic acid metabolism during cherry tomato fruit development. The results showed that fruit nitrate reductase （NR） activity was much higher following treatment with 100% NO3 and 75% NO3 ＋ 25% NH＋ than with 100% NH＋ except at maturity. Glutamine synthetase （GS） activity trended downward during fruit development under all three treatments. Plants fed 100% NH＋ had the lowest fruit citrate and malate levels at maturity, with the highest malate concentration at an early stage. The activity of phosphoenolpyruvate carboxylase （PEPC） was found to be in accord with the malate concentration with every N source. Under all three N forms, the citrate synthase （CS） activity peaked one week before the citrate concentration.

Humic-Like Substances from Different Compost Extracts Could Significantly Promote Cucumber Growth

The effects of direct extracts of compost (DEC), aerated fermentation extracts of compost (AFEC) and non-aerated fermentation extracts of compost (NAFEC) on cucumber growth and the action mechanisms were evaluated based on the structure and activity analysis of humic-like substances. AFEC increased cucumber growth most significantly, followed by DEC and NAFEC, which was insignificant compared to the control treatment. Humic-like substances from compost extracts played an important role in promoting cucumber growth. Application of humic-like substances stimulated auxin-like activity and increased chlorophyll content and nitrogen accumulation in plants. The positive auxin-like activity of humic-like substances could be attributed to the relative distribution of special carbon groups, such as those with a large amount of peptidic and carbohydratic groups or with a low content of phenolic groups. In conclusion, the best growth promotion by application of AFEC was mainly attributed to the humic-like substances in the AFEC.

Aromatic Moieties from Matured Chicken Manure and Agriculture Residues Compost Suppress Growth of Lepidium sativum L. and Trichoderma harzianum

To better understand the role of organic matter(OM)prepared from chicken manure and agriculture residues compost on the growth of plants(Lepidium sativum L.)and antagonistic fungi(Trichoderma harzianum),we analyzed the structure and composition of extracted OM using fluorescence excitation-emission matrix(EEM)spectroscopy and solid-state13C cross-polarization magic-anglespinning nuclear magnetic resonance(13C CPMAS NMR)spectroscopy.The results showed that the EEM contours of water-extracted OM(WEOM)and alkali-extracted OM(AEOM)were similar.Furthermore,solid-state13C CPMAS NMR spectroscopy demonstrated that water extraction could not proportionally pull out aromatic moieties(112–145 ppm)from compost,but the alkali method in proportion extracted both carbohydrates(65–85 ppm)and aromatic moieties.The results suggest that AEOM may better reflect the bulk OM composition of compost,and one should be cautious when applying WEOM as an alternative indicator of total compost OM.Further investigations demonstrated that,compared to carbohydrates,aromatic moieties played a predominant role in growth suppression of Lepidium sativum L.seeds and Trichoderma harzianum.