Antifungal proteins and other mechanisms in the control of sorghum stalk rot and grain mold

Research on antifungal proteins and other mechanisms that provide the biochemical basis for host-plant resistance to stalk rot and grain molds is reviewed in this paper. Stalk rot caused by Fusarium species leads to substantial yield loss due to poor grain filling and/or lodging. A transgenic sorghum expressing high levels of chitinase exhibited less stalk rot development when exposed to conidia of F. thapsinum. Grain mold of sorghum is associated with warm humid environments and results from colonization by several fungi (F. thapsinum, Curvularia lunata, and Alternaria alternata) of the developing caryopsis. The roles of several biochemical mechanisms (tannins, phenolic compounds, red pericarp, proteins, hard endosperm, and antifungal proteins) on grain mold resistance are discussed. Resistance mechanisms related to these compounds appear to be additive, and pyramiding of genes is a feasible approach to limit grain deterioration. Several experimental approaches are proposed to extend current findings.     

Molecular evidence supports hypervariability in Phytophthora colocasiae associated with leaf blight of taro

The oomycete Phytophthora colocasiae that causes taro leaf blight is the most devastating disease of taro and is widely distributed worldwide. Molecular and phenotypic techniques were employed for assessing and exploiting the genetic variability among four populations of P. colocasiae obtained from a fine spatial scale (multiple leaf blight lesions on single taro leaf). Phenotypic characters such as virulence, morphology and mating type showed no variation. ITS characterization revealed detectable polymorphism among isolates of P. colocasiae. The mean number of haplotypes (H), haplotype diversity (HD), nucleotide diversity (π), and nucleotide substitution rate (θ) among analyzed sequences were 6.75, 1.00, 0.069, and 0.088 respectively. High levels of inter and intra specific variation were detected by random amplified polymorphic DNA (RAPD) assays. Moderate genetic diversity (H?=?0.2651) was observed among populations of P. colocasiae. Analysis of molecular variance (AMOVA) confirmed that most of the genetic variability was confined to within a population (63.54 %). The coefficient of genetic differentiation among populations (G _ST ) was 0.2007 and estimates of gene flow (Nm) among populations was 1.991 migrants per generation. Cluster analysis using UPGMA revealed that individuals from the same population failed to cluster in one distinct group. The results of the study reveal considerable genetic diversity among and within populations of P. colocasiae obtained from fine spatial scale. The possible mechanisms and implications of this genetic variation are discussed.     

Emergence of antigenic variants with in serotype A foot and mouth disease virus in India and evaluation of a new vaccine candidate panel

Emergence of genetically and antigenically divergent lineages/genotypes and poor intergenotypic antigenic coverage is a major concern in serotype A foot-and-mouth-disease virus (FMDV) in India. In 2009, to cover antigenic diversity emerged in serotype A virus field isolates, IND40/2000 was selected as the new vaccine strain for incorporation in the trivalent FMD vaccine formulation used in India. Although current vaccine strain (IND40/2000) covers most isolates antigenically, a few VP3(59)-deletion group isolates showed low r-value in routine vaccine matching exercise. The VP3(59)-deletion group within genotype 18 emerged first in late part of 2002 and in 2007 causing outbreaks along with non-deletion isolates of the same genotype. In case of emergence or re-emergence of more antigenically divergent isolates in future, a need for a new vaccine candidate to cover maximum isolates of both deletion and non-deletion group may arise. Four alternate candidate vaccine strains (IND281/2003, IND195/2007, IND360/2007 and IND123/2008) were selected based on set criteria and antigenic relationships with field isolates sampled between 2002 and 2009 were analyzed using a micro-neutralization test. Phylogenetic analysis based on capsid region of serotype A isolates revealed existence of two broad distinct clusters (VP3(59)-deletion and non-deletion group) within genotype 18. The VP3(59)-deletion group has diversified genetically with time giving rise to three different sub-lineages (clade18a, 18b and 18c). The present study indicates that the virus candidates IND281/2003 (VP3(59)-deletion group) and IND195/2007 (non-deletion group) can be used as an adjunct or alternative strain to currently used vaccine strain IND40/2000 in case of emergence of more antigenically divergent isolates in future.     

Host-Specific Toxin Production by Rhizoctonia solani, the Rice Sheath Blight Pathogen

ABSTRACT Rhizoctonia solani, the rice sheath blight pathogen, produces a toxin that reproduces all symptoms of the disease. The toxin has been partially purified and it was found to be a carbohydrate containing glucose, mannose, N-acetylgalactosamine, and N-acetylglucosamine. The toxin was also detected in infected leaves. Highly virulent isolates produced more toxin than less virulent isolates. Several R. solani isolates from rice and one each from cotton and tomato produced a similar toxin. All rice cultivars tested were susceptible to the pathogen and sensitive to the toxin. Host specificity of the toxin has been demonstrated using hosts and nonhosts of the pathogen.     

外源类甜蛋白基因在马铃薯中的表达

将“津引薯８号”马铃薯薄版和含有ＣaMV35S启动子控制的类甜蛋白（ＴＬＰ）基因与紧密连锁的Ｕbiquitin启动子控制的bar标记基因的农植菌双元表达域体进行共培养。切下马铃薯薄片表面产生的幼芽,用含有除草剂bialaphos的ＭＳ培养其进行初步筛选。当获得的生根抗性芽生长成株后用ＴＬＰ蛋白抗体和ＴＬＰ基因特异引我对成株进行间接ＥＬＩＳＡ检测和ＰＣＲ检测。两种检测结果一致率为９０％,推断以bar基因为筛选标记、紧密连锁 的外源类甜蛋白基因已经进入马铃薯基因组并利以表达。     

Effect of FMD vaccine antigen payload on protection, sub-clinical infection and persistence following needle challenge in sheep

The relationship of Foot-and-Mouth Disease (FMD) virus antigen payload and single and double vaccinations in conferring protection against virus challenge in sheep was studied. Sheep vaccinated with half the cattle dose (1 ml) containing 15 and 3.75 μg of FMDV antigen with or without booster resisted virulent challenge on 21 days post vaccination or 7 days post booster. FMDV RNA could be detected in nasal secretions in 26% of vaccinated sheep (10^3.12 to 10^3.82 viral RNA copies) on day 35 post challenge. No live virus could be isolated after 5 days post challenge indicating that the risk of transmission of disease was probably very low. The finding showed that vaccines containing antigen payload of 1.88 μg may prevent or reduce the local virus replication at the oropharynx and shedding of virus from nasal secretions and thereby reduce the amount of virus released into the environment subsequent to exposure to live virus. Sheep with no vaccination or with poor sero conversion to vaccination can be infected without overt clinical signs and became carriers.     

Combining-ability for yield and its components in tomato

In a line × tester analysis in tomato (Lycopersicon esculentum Mill.), the adequacy of 4 testers for combining-ability has been studied. The general and specific combining-ability (GCA and SCA, respectively) variances indicated that the role of non-additive gene action for most of the characteristics and heterosis breeding for the improvement of these traits have been enhanced. LE.758 among the lines and LE.68 among the testers were identified as the best general combiners for yield and its important components. A close agreement between GCA and per se performance was observed among the testers. For selection of hybrids, per se performance as a reliable parameter in preference to SCA effect is indicated.     

Foliar application of Bacillus subtilis AUBS1 reduces sheath blight and triggers defense mechanisms in rice

Journal of Plant Diseases and Protection - Foliar application of Bacillus subtilis strain AUBS1 significantly reduced the sheath blight disease of rice (Oryza sativa L.) under greenhouse...     

利用类甜蛋白基因诱导表达提高马铃薯对晚疫病的抗性研究

将类甜蛋白基因 (TLP)及其紧密连锁的抗除草剂bar基因以农杆菌介导法导入脱毒微型种薯“津引薯 8号” ,经除草剂筛选后的转基因单株无性繁殖用于分子检测 ,标记基因bar基因的PCR反应和含TLP基因特异探针的Southern检测结果 ,转基因植株分别显示出 0 54kb和 3 0kb的特异性条带 ,证明TLP基因已成功地整合到转基因马铃薯基因组中。利用TLP基因特异性抗血清对转基因植株进行Western反应检测 ,结果表明 ,转基因植株中TLP基因表达量显著高于对照组 ,经晚疫病菌游离孢子接种离体抗性分析 ,转基因株系表现出对晚疫病的明显抑制作用和症状发生的延迟作用