枯草芽孢杆菌菌株Czk1挥发性物质的抑菌活性及其组分分析

【目的】明确橡胶树内生枯草芽孢杆菌菌株Czk1挥发性物质的抑菌活性及其组分,为橡胶树病害的生物防治提供参考。【方法】以橡胶树红根病菌GP010为指示菌,分别以5种不同培养基LB、TSB-YE、TSB、NB和PDA为营养来源,利用双皿对扣法和菌丝生长速率法评定不同营养条件下Czk1挥发性物质对病原菌的作用活性强弱,筛选产抑菌挥发性物质的最优培养基;通过双皿对扣法测定Czk1挥发性物质对橡胶树5种根病菌(红根病菌、褐根病菌、白根病菌、紫根病菌和臭根病菌)和橡胶树炭疽病菌的抑菌活性,并利用顶空固相微萃取—气相色谱—质谱法(HSSPME-GC-MS)鉴定Czk1的挥发性物质组分。【结果】在LB培养基中,Czk1在不同浓度下的抑菌活性均优于其他培养基,是Czk1产抑菌挥发性物质的最优培养基。Czk1挥发性物质对6种参试病原菌均表现出良好的抑制作用,Czk1菌液浓度为105 CFU/mL时抑制率均在50.00%以上,Czk1菌液浓度为108 CFU/mL时抑制率在90.00%以上;Czk1挥发性物质可抑制紫根病菌、炭疽病菌和臭根病菌色素的产生,促进褐根病菌产生色素,并导致紫根病菌、褐根病菌和炭疽病菌菌丝生长畸形;其对橡胶树炭疽病菌孢子萌发抑制率为71.30%;其在土壤中对橡胶树红根病菌和褐根病菌仍具有较好的抑菌效果,抑制率分别为63.37%和54.57%。利用HS-SPME-GC-MS对Czk1所产挥发性物质组分进行分析,共分离鉴定获得包括碳氢化合物、胺类、醇类、烯类、酚类、酯类、吡嗪类、醛类、酮类及其他类等33种挥发性物质。【结论】Czk1所产挥发性物质可作为生防资源应用于橡胶树病害防治。

我国咖啡炭疽病菌致病力分化

【目的】明确我国咖啡炭疽病病原菌种类组成、分布及其致病力分化情况,为咖啡炭疽病的有效防治和抗病育种奠定基础。【方法】采用形态学结合ApMat基因序列比对和系统发育进化分析方法,对从我国咖啡种植区典型炭疽病的叶片、枝条、浆果上分离获得的74株炭疽菌病原菌进行鉴定,并采用离体叶片接种法,对所获得的菌株进行致病力测定,分析菌株的致病力差异。【结果】通过形态学及ApMat基因序列比对分析,55个菌株被鉴定为胶孢复合种群,且归为3个种:Colletotrichum siamense、Colletotrichum nupharicola、Colletotrichum theobromicola。致病力试验表明,不同菌种之间的致病力存在差异,Colletotrichum theobromicola的致病力最强,其次是Colletotrichum siamense,最后是Colletotrichum nupharicola。其中,来自海南白沙咖啡种植基地和农业农村部云南瑞丽咖啡种质资源圃的大部分炭疽病菌株致病力属中等以上水平。【结论】我国主要咖啡种植区的55株咖啡炭疽病病原菌均能致病,但致病力分化明显,且与地理来源具有相关性。

剑麻苯丙氨酸裂解酶基因的鉴定及表达分析

剑麻是热带地区重要的纤维作物,但其分子生物学研究基础薄弱,纤维发育机制尚未明确。苯丙氨酸裂解酶(phenylalanine ammonia-lyase,PAL)是纤维重要组分木质素生物合成的起始酶,近年来转录组测序技术快速发展,使开展剑麻PAL基因相关研究更为便利。本文根据已报道转录组数据成功鉴定出2个含完整编码序列的剑麻PAL基因,其在剑麻叶片发育过程中的表达模式与前人报道的PAL在纤维发育过程中的活性变化规律一致,表明其与木质素生物合成密切相关。遗传进化分析结果显示,剑麻和番麻PAL基因进化关系更近,选择压力分析结果显示,剑麻和番麻PAL基因序列选择压力一致且高于太匮龙舌兰PAL基因,这一现象可能由剑麻和番麻纤维性状的趋同进化引起。此外,剑麻PAL基因在铜铅胁迫后差异表达不显著,其可能在重金属胁迫后受到转录后调控。值得一提的是,在烟草疫霉侵染后,剑麻PAL基因表达水平上调倍数较高,其可能同时参与苯丙烷类代谢途径中抗病相关次生代谢产物的合成和细胞壁介导的免疫机制。因此开展剑麻PAL基因功能解析可加深对剑麻纤维发育机制和抗病机制的理解,对培育高产、优质、多抗剑麻新品种具有重要意义。

剑麻麻茎腐解特征及氮素回收利用率研究

为合理利用剑麻麻茎作有机肥还田,采用网袋法和盆栽试验研究了麻茎腐解特性及氮素回收利用率。结果表明,麻茎粉碎还田后240 d,茎部和叶基腐解率均较大,分别高达72.4%、78.9%;茎部氮、磷、钾释放率分别为88.4%、72.7%、94.9%;叶基氮、磷、钾的释放率分别达88.0%、74.4%、95.5%。茎部和叶基快速腐解期均在30 d内,而氮、磷、钾的快速释放期也在30 d内。茎部和叶基不同养分释放速率大小均表现为钾>氮>磷。剑麻吸收的土壤氮比例远高于尿素氮和麻茎氮,而吸收的麻茎氮高于尿素氮。麻茎单施和配施尿素处理的氮素利用率分别为5.1%、4.3%。可见,麻茎还田情况下,可适当降低后茬尿素的用量。

Leaching and Transformation of Nitrogen Fertilizers in Soil After Application of N with Irrigation: A Soil Column Method

A soil column method was used to compare the effect of drip fertigation (the application of fertilizer through drip irrigation systems, DFI) on the leaching loss and transformation of urea-N in soil with that of surface fertilization combined with flood irrigation (SFI), and to study the leaching loss and transformation of three kinds of nitrogen fertilizers (nitrate fertilizer, ammonium fertilizer, and urea fertilizer) in two contrasting soils after the fertigation. In comparison to SFI, DFI decreased leaching loss of urea-N from the soil and increased the mineral N (NH4+-N + NO3- -N) in the soil. The N leached from a clay loam soil ranged from 5.7% to 9.6% of the total N added as fertilizer, whereas for a sandy loam soil they ranged between 16.2% and 30.4%. Leaching losses of mineral N were higher when nitrate fertilizer was used compared to urea or ammonium fertilizer. Compared to the control (without urea addition), on the first day when soils were fertigated with urea, there were increases in NH4+-N in the soils. This confirmed the rapid hydrolysis of urea in soil during fertigation. NH4+-N in soils reached a peak about 5 days after fertigation, and due to nitrification it began to decrease at day 10. After applying NH4+-N fertilizer and urea and during the incubation period, the mineral nitrogen in the soil decreased. This may be related to the occurrence of NH4+-N fixation or volatilization in the soil during the fertigation process.