木薯细菌性枯萎病病原菌的分离与鉴定

采用组织分离法,从发病的木薯叶片上分离纯化病原菌,对纯化的病原菌进行菌落形态、致病性及生化特性的测定,并采用16S r DNA基因序列进行了分子鉴定和进化分析。结果表明,分离的木薯致病菌为黄单胞菌(Xanthomonas sp.)。     

Characterization of pathotypes among isolates of Xanthomonas axonopodis pv. manihotis in Colombia

Cassava bacterial blight, caused by Xanthomonas axonopodis pv. manihotis ( Xam ) is a destructive disease occurring in most cassava growing-areas. Although Colombian isolates of Xam differ in DNA polymorphism and pathogenicity, no suitable host differentials have been identified to demonstrate physiological specialization. A set of 26 Xam isolates from three edaphoclimatic zones (ECZs) in Colombia was selected for inoculation on a set of 17 potential cassava differentials. Leaf inoculation and stem puncture were used in order to detect possible specific interactions between cultivars and isolates. Cultivar × isolate interaction was highly significant ( P  < 0·001) after stem inoculation, but not after leaf inoculation. The stem inoculation technique was selected as a method for resistance screening of cassava cultivars for bacterial blight resistance. A highly significant interaction was also detected when cultivar behaviour was rated as area under the disease progress curve (AUDPC) after stem inoculation. Different pathotypes were defined among the 26 isolates and differential cultivars were proposed to define the pathotypic composition of Xam populations in three ECZs in Colombia. The results should help to improve selection of sources of resistance to cassava bacterial blight.     

Evaluation of a cassava germplasm collection for reaction to three major diseases and the effect on yield

Thirty-five cassava (Manihot esculenta Crantz) genotypes from the International Institute of Tropical Agriculture (IITA), germplasm collection were planted in May 1992 under natural disease infection conditions, at the IITA field plots at Ibadan, Nigeria. The genotypes were evaluated at monthly intervals for six months, for incidence and severity of cassava anthracnose disease (CAD), cassava bacterial blight (CBB) and African cassava mosaic virus (ACMV). The effect of the pathogens on yield was also evaluated twelve months after planting (MAP). CAD, CBB and ACMV incidence and severity were significantly different (P<0.05) among the cassava genotypes at 3 and 6 months after planting. ACMV incidence and severity reached the maximum levels at 3 MAP while CAD and CBB had a low incidence and severity at that period but exhibited a high disease symptom expression at 6 MAP. Yield parameters (plant stand, tuber number, tuber weight and tuber dry matter) differed significantly (P<0.05) between the cassava genotypes. ACMV and CBB severity was negatively correlated with tuber number (r = –0.54 and r = –0.62 respectively). CAD severity was negatively correlated with tuber number (r = –0.46) and tuber weight (r = –0.63). Percentage dry matter was significantly correlated with ACMV severity (r = 0.71), CBB severity (r = 0.63) and CAD severity (r = 0.42). There was also a significant correlation between CBB and ACMD severity (r=0.46) and CBB and CAD severity (r=0.62). Tuber number and yield were significantly correlated (r=0.60), while% dry matter content and root rot showed a significant negative correlation (–0.42).     

应用RAPD技术对44份木薯材料遗传背景的研究

应用RAPD技术对44份木薯材料的遗传背景进行研究。结果表明,采用筛选出的19条随机引物(10bp)PCR扩增共获得279条带,其中234条出现多态性。引物S32和S76可将供试44份材料全部区分开。计算出44份木薯材料的成对相似系数,绝大多数栽培材料间的相似系数大于0.75。通过UPGMA聚类分析,将44份木薯材料划分为野生种和栽培种2大类,依结合线不同,栽培材料又可细分为若干个类群。不同国家和地区来源的材料不能明显聚类。对中国热带农业科学院自身育成的材料单独进行UPGMA聚类,结果与系谱相吻合。利用RAPD研究结果对部分木薯材料的亲缘关系进行了鉴定,并探讨了RAPD技术运用于木薯育种中亲本选配的可能性。      

木薯的营养特性及平衡施肥

采用田间小区试验和大田对比试验的方法,对木薯的营养规律、平衡施肥中的ＮＰＫ比例及最隹施肥量进行了多年的研究。结果表明：木薯生长从土壤中带走的Ｎ∶Ｐ∶Ｋ∶Ｃａ∶Ｍｇ比例为１∶０．１∶０．６５∶０．４１∶０．１９,块根中Ｎ∶Ｐ∶Ｋ∶Ｃａ∶Ｍｇ为１∶０．２∶１．９∶０．３∶０．２;在花岗岩砖红壤上木薯平衡施肥适宜的Ｎ∶Ｐ２Ｏ５∶Ｋ２Ｏ比例为２∶１∶３或２∶１∶２,最隹的施肥量为４５０ｋｇ／ｈｍ２。     

木薯饲用型品种的筛选

通过正交试验法,对现有的木薯优良品系进行对比,以筛选出适宜于刈割的饲用型新品种以及对应的配套栽培技术。试验结果表明：木薯新品系ＺＭ９０３６和ＺＭ８６３９在块根产量、茎叶产量、茎叶粗蛋白产量以及抗风能力等主要特性方面均相当或超过对照种华南２０５,可进一步示范推广。植后４－８个月对植株进行刈割则对块根产量造成较大的影响,在这段时间里摘顶时间越早对块根产量的影响越大。但通过刈割可大大提高木薯嫩茎叶和粗蛋白的产量,同时可大大增强植株的抗风能力。     

单行木薯块根收获机仿生铲的设计与试验

针对目前木薯块根收获机挖掘铲存在入土困难、碎土及排土效果不理想及工作强度不足等问题,基于工程仿生学理论,结合动力学知识,提出并设计了一种模仿犬爪趾形状的仿生铲.基于Design-Expert软件中的试验设计方法,以作业速度、土壤含水率及挖掘铲类型为试验因素,以挖薯率、伤薯率为试验指标,对挖掘铲的工作参数进行试验研究,建...     

华南205木薯二倍体及其同源四倍体对朱砂叶螨取食胁迫的生理响应

为明确木薯同源四倍体抗螨的生理机制,以华南205（South China 205,SC205）木薯的二倍体及其同源四倍体为试验材料,分别于朱砂叶螨Tetranychus cinnabarinus取食胁迫前（取食0 d）及取食胁迫后1、4和8 d观察两个倍性植株叶片的受害情况并测量叶片中叶绿素、游离脯氨酸、丙二醛（malondialdehyde,MDA）、次生代谢物质含量和主要保护酶活性的变化。结果显示,朱砂叶螨取食胁迫后SC205四倍体叶片受害情况较SC205二倍体的轻;取食胁迫后1、4和8 d木薯SC205四倍体叶片中叶绿素含量下降幅度比SC205二倍体的小;取食胁迫后1、4和8 d两个倍性木薯叶片中MDA和游离脯氨酸含量均呈上升的趋势,其中SC205四倍体叶片中MDA含量的上升幅度比SC205二倍体的小,而游离脯氨酸含量的上升幅度比SC205二倍体的大;取食胁迫后1、4和8 d两个倍性木薯叶片中过氧化氢酶（catalase,CAT）、超氧化物歧化酶（superoxide dismutase,SOD）、过氧化物酶（peroxidase,POD）活性和单宁、总酚、总黄酮含量较取食胁迫前均显著上升,且SC205四倍体的上升幅度比SC205二倍体的大。表明木薯同源四倍体植株的抗螨性与叶绿素、游离脯氨酸、MDA、保护酶活性及次生代谢物质含量变化有关,它们均参与了木薯对朱砂叶螨取食胁迫的诱导型防御反应。     

类黄酮合成关键基因MeF3H在木薯块根采后腐烂中的功能分析

为探究MeF3H在木薯块根采后生理腐烂（PPD）中的功能,以‘华南9号’（‘SC 9’）为试验材料,通过qRT-PCR技术分析MeF3H在叶片、叶柄、茎、脆性胚性愈伤组织（FEC）、花、腋芽、纤维根、块根及块根PPD中的表达情况,确定MeF3H的亚细胞定位,结合病毒诱导的基因沉默（virus-induced gene silencing,VIGS）分析MeF3H沉默后块根中类黄酮含量及块根腐烂情况。结果表明,MeF3H在腋芽及纤维根中高表达,MeF3H定位在细胞质,MeF3H基因表达及块根中类黄酮含量随着PPD程度加深而升高。qRT-PCR结果显示MeF3H沉默效率在39%~67%。MeF3H沉默后,与对照植株相比,沉默植株叶片及块根中类黄酮含量均显著下降（P<0.05）,且MeF3H基因表达与块根中类黄酮含量呈显著正相关（P<0.05）。在采后储存第3天,块根超过50%的面积出现腐烂,而对照植株块根腐烂率为36.67%。综上,MeF3H表达与木薯块根中类黄酮含量及块根耐PPD能力存在显著正相关（P<0.05）,MeF3H基因沉默后导致木薯块根PPD显著加速。     

不同灌溉处理对木薯农艺性状的影响

研究了在不同土壤相对含水量条件下木薯的农艺性状的表现。结果表明,随着时间的延长,各灌溉处理木薯的株高和径粗都比对照高,其中以苗期和块根成熟期下限田间持水量50%与块根形成期和块根膨大期田间持水量65%的处理表现为最高值。木薯株高和径粗在7月27日至8月16日间生长速度较高,之后通过灌溉,各灌溉处理木薯的生长率均高于对照,说明水分灌溉对木薯的农艺性状有良好的促进作用。