旱稻孢囊线虫生活史及侵染特性

 以2龄幼虫人工接种水稻幼苗和田间定点调查的方法,研究了旱稻孢囊线虫的生活史和侵染特性。结果表明,在30℃下接种后24 h内,2龄幼虫大多聚集在根尖分生区或伸长区,接种后24 h可侵入根系,侵入后虫体在中柱建立取食点;接种后6 d,2 龄幼虫发育成白雌虫,8 d发育成雄虫,12 d雌虫从阴门处产生胶状物质,雌虫的一部分卵产于胶质卵囊中。接种后18 d,胶质卵囊中的2龄幼虫开始孵化。在30℃下,旱稻孢囊线虫从卵到卵的最短生活周期为22 d;从接种到2龄幼虫从胶质卵囊中孵出,最短生活周期为18 d。20℃下线虫发育缓慢。较高温度如28℃~35℃有利于2龄幼虫的侵染和发育。淹水条件不利于2龄幼虫的侵染,但对孢囊的发育无显著影响。     

玉米孢囊线虫孵化特性及不同品种玉米对其抗性研究

玉米孢囊线虫病是我国玉米的新病害，对我国玉米生产存在潜在风险。通过生物学测定和盆栽试验，研究广西玉米孢囊线虫(Heterodera zeae)群体孵化特性、侵染规律和发育进程以及广西主栽玉米品种对该线虫群体的抗性。结果表明，玉米孢囊线虫在25℃～33℃均可孵化，33℃为最佳孵化温度；20℃和35℃条件下孢囊线虫的孵化率仅为4.6 %；15℃和40℃条件孢囊不孵化。30℃条件下，玉米孢囊线虫15～18 d完成1个生活史。广西主栽的16个玉米品种中仅有庆农13和万川973表现为高抗。     

拟禾本科根结线虫对水稻根系的侵染特性及其生活史

在人工接种情况下,利用次氯酸钠-酸性品红染色方法,研究拟禾本科根结线虫对汕优63杂交稻幼苗根系的侵染特性及其生活史。结果表明:在26℃大量群体接种情况下,2龄线虫在接种后4～6 h内侵入根系,主要侵入时间为接种后24～48 h;2龄幼虫侵入部位为根尖分生区或伸长区,侵入后虫体迁移方向与根纵中轴平行,在皮层薄壁细胞间迁移,最终聚集于根冠最内侧的分生区,直待分生区原形成层发育成维管束后,2龄幼虫才侵入维管束内取食;根冠内侧分生区至伸长区的2龄幼虫呈侵染态线状至长颈瓶状逐渐发育膨大过程,其发育快慢可能与2龄幼虫开始定殖并侵入维管来取食时间先后有紧密关系;2龄幼虫可直接在根内孵化,并迁移至发育中的侧根,或迁移到新根根冠内侧分生区处,待分生区原形成层发育成维管束后进行再侵染;拟禾科根结线虫最短生活史在26℃下为22 d,在26～37℃环境温度下为18 d,其侵染具有群体优势特性。     

禾谷孢囊线虫的田间侵染规律及垂直分布研究

为了解禾谷孢囊线虫(CCN)在小麦田间的侵染规律和分布动态,在2010-2012年的两个冬小麦生育周期里,定点调查CCN(Heterodera avenae)江苏沛县群体的田间生活史及不同虫态的数量.结果表明,在小麦生长季节中CCN只能完成一代生活史;小麦越冬前有少量二龄幼虫(J2)孵化,能侵入根系,但不能正常发育;返青期小麦的根围土壤中出现J2孵化高峰,大量侵入根系后,至抽穗期完成发育,在根系上形成肉眼可见的白色雌虫,在根内及土中可见少量雄虫;小麦成熟收获期,白色雌虫开始变褐形成孢囊,落入土中越夏.从田间垂直分布调查结果看,田间孢囊主要分布在土表下0～10 cm土层,孢囊线虫孵化的J2也主要分布在0～10 cm土层中,并且在返青期出现高峰,这与CCN的田间侵染规律相吻合.     

休闲与轮作对燕麦孢囊线虫种群动态的影响

为明确休闲与轮作对燕麦孢囊线虫病害的防治效果,通过盆栽模拟和田间试验相结合的方法,分析了土壤休闲、轮作和连作对燕麦孢囊线虫种群动态的影响。结果表明,燕麦孢囊线虫的孵化不受寄主或寄主种类的影响;不同处理土壤中二龄幼虫数量以及孢囊内的虫口密度变化趋势一致,河北地区燕麦孢囊线虫孵化高峰期主要在3-4月份。休闲一年后燕麦孢囊线虫的减退率为89.8%。小麦与茄子、甜瓜和冬瓜轮作一年后线虫减退率分别为93.8%、90.7%和90.7%,轮作二年后线虫减退率为98.8%。在自然病田,小麦连作一年后虫口密度上升36.8%,连作两年后虫口密度上升49.2%。说明小麦连作后燕麦孢囊线虫的发生呈上升趋势,休闲或轮作一年以上可有效地降低土壤中燕麦孢囊线虫的虫口密度。     

麦类作物线虫病的研究现状及对策

本文阐述了麦类作物主要线虫病及其有关症状、发生规律等新的研究进展。研究指出小麦粒瘿线虫对寄主有特异性识别作用.侵染后寄主的新陈代谢受到干扰。粒瘿线虫、燕麦孢囊、根结、根腐等线虫.可与细菌、真菌造成复合侵染加重为害。它们大都存在生理分化现象,轮作与抗病育种时应予以注意。穿刺巴氏芽孢杆菌、厚垣孢轮枝菌、嗜雌线疫霉菌对燕麦孢囊和根结线虫的雌虫和卵有一定生防作用.可进一步研究应用。     

荔枝霜疫霉的生物学特性

通过不同培养基和培养条件的筛选,研究荔枝霜疫霉的生物学特性及病菌侵染的超微形态特征.结果表明,该菌的孢囊梗属于多级有限生长,其孢子囊萌发后形成多种真菌形态,如游动孢子、芽管、孢囊梗及次生孢子囊:芽孔位于孢子囊一端、两端或四周,在1个芽孔处可萌发1根、2根或多根芽管,位于基部的芽孔萌发能力较强.该菌培养35 d后可产生厚垣孢子.培养45 d可产生大量的卵孢子,菌龄为10 d时产生孢子囊的萌发率最高.温度为16～24℃时孢子囊萌发形成游动孢子,在26℃以上萌发形成芽管.该菌在PDA培养基上的产孢量最高,在燕麦培养基上的生长速度最快.生长的最适pH值为6～8.超微形态研究结果表明,该菌可通过孢子囊及游动孢子从荔枝果皮的嵴点裂缝处与皮孔处侵入,并在果皮内扩展,直到荔枝的内果皮.试验结果加深了对该病菌的了解,为进一步了解该病的发生危害提供了理论依据.     

甘肃天祝农牧区燕麦田孢囊线虫调查及种类鉴定

为了明确甘肃天祝农牧区燕麦田孢囊线虫的发生情况及种类,2014年8-9月,采用Z字型取样法,对天祝燕麦主要种植区进行了调查。结果表明,采集到的80份燕麦根际土样中孢囊线虫发生率为44%,孢囊密度为4.3个·100g-1土样。安远镇的发生率最高,为54.2%,华藏寺的发生率最低,为14.3%。孢囊浅褐色,阔柠檬形,长571μm(447~727μm),宽449μm(375~595μm)。阴门双膜孔,膜孔长31μm(28~33μm),膜孔宽16μm(13~20μm),阴门裂长9μm(8~11μm),泡状突明显,未见阴门下桥。天祝5个乡镇孢囊线虫rDNA-ITS区片段长度均为1 045bp,经Blast比对发现,所测序列与燕麦孢囊线虫(Heterodera avenae)的ITS序列相似度达99%~100%。系统进化关系分析显示,天祝孢囊线虫与国内及国外燕麦孢囊线虫在同一个大的进化分支,与中国的燕麦孢囊线虫在同一个小的分支。因此,形态特征结合rDNA-ITS序列分析将甘肃天祝燕麦田的孢囊线虫鉴定为燕麦孢囊线虫。     

温度和湿度及水稻不同生育期对水稻干尖线虫垂直迁移的影响

  研究了不同温度和湿度对水稻干尖线虫垂直迁移的影响以及线虫在水稻不同生育期生长繁殖和垂直分布状况。结果表明,线虫迁移的最适温度为25～30℃。在温度适宜的条件下,相对湿度越高,线虫迁移率越高。温室接种实验表明水稻拔节期线虫主要分布在接种点周围及水稻上部,且虫量递减明显,20 d后线虫虫量仅为接种5 d时的50%。孕穗期线虫主要分布在水稻的幼穗中,并且大量繁殖,20 d后线虫虫量为接种5 d时虫量的3倍。     

大豆根结部位内源激素对线虫侵染的响应

通过酶联免疫法(ELISA)测定南方根结线虫侵染大豆根系后,根结部位赤霉素(GA)、玉米素核苷(ZR)、生长素(IAA)、脱落酸(ABA)和茉莉酸甲酯(JA-Me)5种内源激素的含量变化,从而探索寄主对线虫侵染的激素应答反应。研究结果显示:在根结形成过程中,根结内5种内源激素含量均发生变化,其中JA-Me和ZR在线虫侵染发育的28d内持续高于对照;在接种线虫5d内,根结内IAA含量显著高于对照,而ABA则显著低于对照;在接种5d后IAA含量一直低于对照;ABA只在接种14d左右显著高于对照,而GA只在接种21d左右显著高于对照,其他时间ABA和GA与对照基本一致。分析上述5种内源激素间平衡关系表明:IAA/ABA和JA-Me/ABA的比值变化明显,ZR/ABA和GA/ABA的比值平稳。研究结果暗示IAA、ABA和JA-Me在线虫侵染大豆形成根结过程中发挥了更重要的作用。     

温度对马铃薯花药愈伤诱导率的影响

采用讷16、克新16、克新13和西北果4个马铃薯品种或品系为试验材料,研究不同温度处理对马铃薯花药愈伤组织形成的影响。研究表明,接种前花蕾经2～8d、4℃低温预处理有利于花药愈伤组织的形成,其中以2～4d处理的效果最好,接种后经24～48h、32℃热激处理有利于花药愈伤组织的形成。试验还对低温预处理和热激处理相配合的效果进行了比较,发现两者配合处理的效果好于单独处理,单独热激处理的效果好于单独低温预处理。     

藤本豆根结线虫病的病原鉴定及其侵染特性的研究

在福建省发现豆科新品种多年生藤本豆（Lablab sp.）发生严重的根结线虫病,根部可产生巨大根结,根结内组织内可埋生数以百计的雌虫,卵囊产于根结内。通过形态特征及rDNA-ITS区序列扩增比对,藤本豆根结线虫鉴定为南方根结线虫（Meloidogyne incognita）。多年生藤本豆受根结线虫为害为首次记述, 也是南方根结线虫新寄主。接种实验结果表明,2龄幼虫主要侵染藤本豆根尖,也可侵染根其他部位,雌虫与卵囊埋生于根结内,卵可直接孵化并在根内直接侵染发育,根结大小发展快,根结坚硬,表面组织不易腐解,雄虫只能在后期根结腐败组织处发现。在环境温度（24~36 ℃）,生活史最短为24 d。田间重要杂草空心莲子草（Alternanthera philoxeroides）根结线虫病发生普遍,形态特征鉴定为南方根结线虫,田间调查及交叉接种实验表明其可能为田间藤本豆根结线虫病的主要侵染来源。     

Relation between growth conditions and dormancy of seed potatoes. 2. Effects of temperature

Summary In two indoor experiments under short day conditions, the effect of temperature during tuber bulking on dormancy of tubers was investigated for cvs Diamant and Désirée. Temperature treatments started after tuber initiation and lasted for 4 weeks, after which the haulm was removed. In Experiment 1, the day/night temperature regimes 18/12, 22/22, 26/18 and 32/12 °C (T18/12 etc.) were compared. In Experiment 2, three day temperatures (18, 24 and 30 °C) were combined with three night temperatures (12, 18 and 24 °C), resulting in nine treatments. The dormancy of cv. Diamant was shortest after very high day temperatures (30–32 °C), but intermediate day temperatures (22–26 °C) had no shortening effect compared to T18/12. Dormancy of cv. Désirée was not shortened, but rather tended to be prolonged by high temperatures (22–32 °C) during growth. High temperatures during growth resulted in more sprouts per tuber after dormancy had ended.     

Effects of Temperature, Humidity and Different Rice Growth Stages on Vertical Migration of Aphelenchoides besseyi

The vertical migration of Aphelenchoides besseyi under different temperatures and humidities and at different rice growth stages was investigated. It was found that the optimum temperature for the development and reproduction of A. besseyi was 25-30°C. At the same temperature, the rate of vertical migration increased with rising relative humidity. Artificial inoculation tests showed that at the elongation stage, nematodes survived mainly on the upper and middle parts of rice culms, and the number of nematodes decreased by 50% at 20 days after inoculation compared with that at 5 days after inoculation. Whereas at the booting stage, nematodes accumulated in young panicles and reproduced quickly, and the average number of nematodes at 20 days after inoculation increased to 164.5, three times of that at 5 days after inoculation.     

The effect of temperature on the development of wilting and on progeny tuber infection of potatoes inoculated with South African strains of biovar 2 and 3 ofPseudomonas solanacearum

Summary Potato plants, after inoculation with a South African strain of biovar 2 or a strain of biovar 3 ofPseudomonas solanacearum were grown in growth chambers at temperatures ranging from 14/16°C (dark/light) up to 25/30°C. When grown at 14/16°C or higher, plants inoculated with the biovar 2 strain developed wilting symptoms and internal symptoms on progeny tubers and the disease was transmitted by the progeny tubers. When the plants were inoculated with the biovar 3 strain, wilting symptoms developed from 18/20°C, internal symptoms on progeny tubers from 20/22°C and the disease was transmitted by progeny tubers from plants grown at 16/18°C or higher.     

温度对芒果小爪螨实验种群增长的影响

在16,20,24,28,32℃条件下观察芒果小爪螨的发育、存活及繁殖情况。结果表明:芒果小爪螨世代发育历期在32℃时最短,为9.20d,16℃时最长,为29.07d。卵、幼螨、若螨、产卵前期及世代的发育起点温度分别为8.77,9.37,10.61,11.13,8.91℃,有效积温分别为93.46,30.29,44.96,14.24,191.83日度,在16～32℃,芒果小爪螨发育的速率及雌螨寿命与温度呈直线相关。世代存活率在24℃时最高,为89.6%,32℃和16℃时,分别降至69.1%和55.8%。雌螨产卵量在28℃时最高,达40.14粒/雌,在32℃时最低,为8.44粒/雌。卵孵化率、幼螨、若螨及世代存活率、雌螨产卵量等随温度的上升而呈抛物线趋势。净增殖率(R0)、内禀增长率(rm)、周限增长率(λ)等种群特征参数以28℃时最高,分别为27.3342,0.3957,1.4854。平均世代历期和种群加倍时间分别以32℃和28℃时最短,分别为7.5186d,1.7517d。种群增长指数以24℃时最高,28℃时略低,分别为24.88和24.45。芒果小爪螨对温度较敏感,24～28℃为芒果小爪螨种群增长的最适温度。     

Effect of photoperiod and temperature on resistance againstPhytophthora infestans in susceptible and resistant potato cultivars: Effect on deposition of structural phenolics on the cell wall and resistance to penetration

Deposition of phenolic compounds before and after inoculation withPhytophthora infestans was evaluated in two Mexican cultivars (Malinche and Tollocan) with major unknown R genes for resistance to potato late blight, two cultivars (393295.236=CIP1 and 391046.22=CIP2) without R genes from the International Potato Center (CIP) and the susceptible cultivar Atlantic. Before inoculation, plants were grown in growth chambers at two temperatures (16 or 24 C) and two photoperiods (PPD 12 or 16 h day length). Forty-eight hours after inoculation, the number of penetrations was recorded and depositions of phenolic compounds were classified according to detection and location in (a) the anticlinal cell wall, (b) the whole cell, (c) the stomatal cells, and (d) without detectable depositions of phenolic compounds. The concentration of phenolic compounds in the epidermal cells was slightly increased at 16 C and 16 h PPD and penetration frequency was lower at 16 C (12 h PPD). Concentration of phenolic compounds was not correlated with penetration frequency, but was correlated with the resistance level of the different potato cultivars. Atlantic had the highest number of penetrations followed by Tollocan, CIP1, CIP2, and Malinche. The cytological observations indicated that four types of deposition of phenolic compounds occurred in all five potato cultivars irrespective of their type and level of resistance. These results suggest that deposition of phenolic compounds on epidermal cells is a general resistance mechanism in potato leaves that does not have a specific relation with resistance to the penetration ofP. infestans. Phenolic depositions were intrinsically similar in potato cultivars with and without R genes, which stresses the difficulty in differentiating between horizontal and vertical resistance.     

The effect of soil pH on yield losses caused by the potato cyst nematodeGlobodera pallida

Summary The effect of soil pH on yield losses due to potato cyst nematodes (Globodera pallida) was investigated in experiments in the field and in a semi-controlled environment. Through annually liming a reclaimed peat soil with about 22% organic matter, plots with pH levels of 4.5, 5.0, 5.5, 6.0 and 6.5 were obtained. In 1990 potato yields in these plots decreased from 45 t/ha at pH 4.5 to 33 t/ha at pH 6.5, whereas the nematode densitites decreased from about 18 to 9 juveniles per g soil. In a container experiment a strong interaction was recorded between soil pH and the presence of nematodes. Tuber yields were about 11% lower at pH 6.5 than at pH 4.5 in the absence of nematodes, but about 44% lower when an initial population of 27 juveniles per g soil was present.