Host specificity of Sporisorium reilianum is tightly linked to generation of the phytoalexin luteolinidin by Sorghum bicolor

The smut fungus Sporisorium reilianum occurs in two varieties (S. reilianum f. sp. reilianum and S. reilianum f. sp. zeae) that cause head smut disease on sorghum and maize, respectively. Prior to plant infection, compatible haploid sporidia of S. reilianum fuse to form infectious dikaryotic hyphae that penetrate the leaf surface, spread throughout the plant, and reach the inflorescences, in which spore formation occurs. To elucidate the basis of host specificity of the two S. reilianum varieties, we compared disease etiology of S. reilianum f. sp. reilianum and S. reilianum f. sp. zeae on sorghum and maize. Both varieties could penetrate and multiply in both hosts. However, red spots appeared on inoculated leaves after sorghum infection with S. reilianum f. sp. zeae. Using matrix-assisted laser desorption-ionization time of flight analysis of leaf extracts, we show that sorghum reacts with the production of the red and orange phytoalexins luteolinidin and apigeninidin upon colonization by S. reilianum f. sp. zeae but not by S. reilianum f. sp. reilianum. Using in vitro growth assays, we demonstrate that luteolinidin but not apigeninidin slows vegetative growth of both S. reilianum f. sp. zeae and S. reilianum f. sp. reilianum. However, the phytoalexin biosynthesis gene SbDFR3 is only induced in sorghum after infection with S. reilianum f. sp. zeae, as shown by quantitative real-time polymerase chain reaction. This suggests that regulation of luteolinidin biosynthesis determines infection success of S. reilianum on sorghum.     

Identification of a New Race of Sporisorium reilianum and Characterization of the Reaction of Sorghum Lines to Four Races of the Head Smut Pathogen

Sporisorium reilianum is the causal agent of head smut on sorghum and maize. In order to effectively utilize host resistance to control this important disease in crops, it is necessary to monitor changes in disease dynamics and virulence of the pathogen. An outbreak of head smut was recently observed in a sorghum field, near Gaoping, Shanxi, China, and research was undertaken to characterize a putative new race of S. reilianum. A set of differential sorghum lines with resistance to several conventional races was used to characterize the newly collected isolate of S. reilianum. The reactions of differential cultivars/germplasm lines to the new isolate indicate that it is a new physiological race of S. reilianum. The new race is highly virulent on sorghum line A₂V4 and its hybrid, Jinza 12, that are known as resistant to all existing Chinese races of S. reilianum, including races 1, 2, and 3. The new isolate of S. reilianum is different from all of the described races of the pathogen; thus, it is designated as race 4 of S. reilianum. Furthermore, a collection of 34 sorghum genotypes including commercial cultivars and germplasm lines was evaluated for disease reaction to the newly described race and the three known races of the pathogen.     

Microbial Changes in Sweet Sorghum (Sorghum bicolor) Juices

Juice freshly expressed from Sorghum bicolor for making sweet sorghum syrup contained 10⁸ microorganisms per ml. The dominant bacterium was Leuconostoc mesenteroides, followed by gram-negative rods. Lactobacilli, yeasts, and nonfecal coliform bacteria each comprised about 1% of the microbial population. Spoilage of juice, manifested by a sour odor, discoloration, and foaming, occurred between 5 and 12 h at ambient temperatures. Spoilage was correlated with a drop in pH from 4.9 to 4.5 L. mesenteroides was the dominant spoiling agent at 20°C, and Lactobacillus plantarum was the dominant spoiling agent at 32°C, as determined by pure culture studies. Juice may be stored for 14 days at 4°C if promptly refrigerated.     

高粱抗丝黑穗病基因的RAPD初步分析

目的：对高粱抗丝黑穗病的基因进行分析。方法：以高粱2381恢复系（抗病）、矮四恢复系（感病）、7050B保持系（抗病）、TX622B保持系（感病）为材料,采用CTAB提取DNA的方法提取高粱基因组DNA,然后应用RAPD分子标记技术对DNA进行多态性扩增。结果：初步建立了高粱丝黑穗病的RAPD反应体系;从RAPD反应中所用的48个随机引物中筛选出28个适宜引物,其余20个引物没有扩增出谱带,被淘汰;共扩增出114条谱带,其中引物OPM-05300和OPM-13450扩增出了差异谱带,分别命名为OPM-05300和OPM-13450。结论：在该反应体系下找到了高粱抗丝黑穗病抗感品种间基因组差异的两条差异谱带。     

高粱抗丝黑穗病SSR-PCR反应体系的优化

目的:找到一种可用于高粱抗丝黑穗病SSR-PCR扩增最适宜的反应体系。方法:利用单因素体系优化的方法,对SSR-PCR反应体系中Taq酶、dNTPs、MgCl2、模板DNA以及引物用量进行了优化,并且用不同引物、不同模板DNA对该优化结果进行验证。结果:实验表明,Taq酶、dNTPs、MgCl2、模板DNA以及引物的不同用量均对PCR反应结果有显著的影响。最适宜高粱抗丝黑穗病20μl SSR-PCR的反应体系为1U/μl Taq酶2.5μl,10mmol/L dNTPs 1.0μl,25mmol/L MgCl21.5μl,模版DNA2.0μl(50ng),10μmol/L引物1.5μl,10×Buffer 2.0μl。验证结果表明,该体系扩增出的条带清晰且稳定。结论:该结果为今后利用SSR-PCR标记技术研究分析高粱抗丝黑穗病奠定了基础。     

Effects of Ring D-Modified Gibberellins on Gibberellin Levels and Development in Selected Sorghum bicolor Maturity Genotypes

Plants of early flowering mutant and wild type genotypes of Sorghum bicolor were treated with ring D-modified gibberellins (GAs), and the effects on endogenous GA levels were determined. The growth and timing of floral initiation in 58M plants grown under 18-h days (which significantly delays floral initiation in this short day plant) following treatment with these compounds, relative to GA₃ and GA₅ treatments, were also investigated. Application of the endo-isomer of C16,17-dihydro-GA₅ (endo-DiHGA₅), the exo-isomer of C16,17-dihydro-GA₅ (exo-DiHGA₅), and C16α,17-dichloromethanodihydro-GA₅ (DMDGA₅) altered GA levels in both genotypes. Each ring D-modified GA significantly inhibited shoot growth while significantly decreasing levels of GA₁ and increasing levels of its immediate precursor, GA₂₀. Gibberellin A₈ levels also decreased. Tillering was not affected by any treatment. For the early flowering genotype 58M, grown under noninductive long days, both dihydro-GA₅ isomers promoted floral initiation while shoot growth was strongly inhibited, and floral development was strongly advanced beyond floral stage 4. Gibberellin A₃ and GA₅, applied under the same conditions, promoted shoot growth slightly and gave ``floral-like' apical meristems that did not develop past floral stage 1. These results suggest that the reduced shoot growth of sorghum, which follows application of those ring D-modified GAs, is due to their inhibiting the 3β hydroxylation of GA₂₀ to GA₁, thereby reducing the GA₁ content. That floral initiation was hastened and floral development promoted in genotype 58M by application of both isomers of DiHGA₅ are in contrast to the effects of other GA biosynthesis inhibitors, which act earlier in the GA biosynthesis pathway, but are consistent with results seen for long day grasses. This suggests that endo-DiHGA₅ and exo-DiHGA₅ may be acting directly in promoting floral initiation and subsequent floral apex development of this short day plant under long day conditions. Received October 3, 1996; accepted January 22, 1997     

Sorghum (Sorghum bicolor) varieties adopt strongly contrasting strategies in response to drought

Sorghum is one of the most drought tolerant crops but surprisingly, little is known about the mechanisms achieving this. We have compared physiological and biochemical responses to drought in two sorghum cultivars with contrasting drought tolerance. These closely related cultivars have starkly contrasting responses to water deficit. In the less tolerant Samsorg 40, drought induced progressive loss of photosynthesis. The more drought tolerant Samsorg 17 maintained photosynthesis, transpiration and chlorophyll content until the most extreme conditions. In Samsorg 40, there was a highly specific down‐regulation of selected proteins, with loss of PSII and Rubisco but maintenance of PSI and cytochrome b₆f, allowing plants to maintain ATP synthesis. The nitrogen released allows for accumulation of glycine betaine and proline. To the best of our knowledge, this is the first example of specific reengineering of the photosynthetic apparatus in response to drought. In contrast, in Samsorg 17 we detected no substantial change in the photosynthetic apparatus. Rather, plants showed constitutively high soluble sugar concentration, enabling them to maintain transpiration and photosynthesis, even in extremely dry conditions. The implications for these strikingly contrasted strategies are discussed in relation to agricultural and natural systems.     

Effect of proteolytic and glycolytic enzymes on a factor inSorghum bicolor that induces mycelial growth in the smut fungus,Sporisorium reilianum

Proteins obtained from seedling shoots and floral meristems ofSorghum bicolor (L.) Moench cv. NK 1210 induced mycelial growth in the smut fungus,Sporisorium reilianum in vitro. Proteins precipitated with trichloroacetic acid and ammonium sulfate were equally effective as inducers, although there were minor variations in the pattern of mycelial growth. Hydrolysis of the protein fraction with the proteolytic enzyme pronase E resulted in considerable reduction in the proteins' ability to induce mycelial growth. Digestion of the protein fraction with driselase, resulted in a slight enhancement of biological activity. The results suggest that amino sugar moieties in glycoproteins may act as inducers of mycelial growth inSporisorium reilianum.     

高粱对丝黑穗病的抗性及遗传研究

1981—1985年在人工接种的条件下,对1239份高粱品种资源,进行了抗丝黑穗病性鉴定。与此同时,用17个抗性不同的品种系,按照不完全双列杂交设计,进行了高粱对丝黑穗病的抗性遗传研究。结果表明,高粱对丝黑穗病的抗性遗传方式因品种而异。有的品种系具数量性状遗传特点,有的则具有质量性状遗传特点。抗病性属数量性状遗传的品种系,其抗性主要是受加性基因控制。     

Study of the intracellular xylanolytic activity of the phytopathogenic fungus Sporisorium reilianum

The present study demonstrates that Sporisorium reilianum, a phytopathogenic fungus of corn, produces intracellular xylanolytic activity during submerged fermentation. Production reached its highest levels in a medium containing glucose, corn hemicellulose and yeast extract. An intracellular xylanase was purified by a process that included precipitation with ammonium sulfate, ion exchange chromatography and gel filtration. Optimal pH and temperature values were 5.0 and 60 °C, respectively. The enzyme showed activity through a broad pH range. The molecular weights of pure xylanase were 36 and 37 kDa, determined by SDS PAGE and gel filtration, respectively. K_m and V_max were 0.160 mg/mL and 1.564 μmol/min/mg, respectively, on a substrate of birchwood xylan. SDS, EDTA, β-Mercaptoethanol, Tween 80, Triton and Mn²⁺ and Ca²⁺ strongly inhibited activity. The purified enzyme hydrolyzed xylan, releasing xylotriose and xylobiose. Sequence protein analysis showed 95% similarity with the theoretical protein encoded by the sr14403 gene of S. reilianum, which encodes a putative endo-β-1,4-xylanase. The enzyme is an isoform of the extracellular xylanase SRXL1 of this basidiomycete.     

Biochemical changes during seed development in sorghum (Sorghum bicolor)

Grain dry weight accumulation, soluble sugars, starch, protein, fat and ash contents were studied in developing grains of eight sorghum cultivars. The     

High Frequency Shoot Organogenesis in Sorghum bicolor (L) Moench

In vitro morphogenesis that includes enlargement of apical meristems and differentiation of shoot buds on the surface of enlarged meristemoids, have been observed in Sorghum bicolor. The enlargement of apical meristems occurred on the MS medium containing different auxins [2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichloro-phenoxyacetic acid (2,4,5-T) and parachlorophenoxyacetic acid (pCPA)] with or without 6-benzylaminopurine (BAP)]. Large number of shoot buds arose over the entire surface of enlarged, green, compact, nodular, hard and shiny meristemoids on transfer to medium containing BAP (2.0 mg l^?1) + (IAA) indole 3-acetic acid (0.5 mg l^-1). Histological observations revealed the origin of shoot apices from the surface of enlarged meristemoids. Efficient rooting was achieved onto half-strength MS medium supplemented with α-napthaleneacetic acid (NAA, 2.0 mg l^?1) and sucrose 2% (w/v). Plantlets were transferred to earthen pots under field conditions for the evalution of several agronomically important characters.     

高粱抗丝黑穗病基因SSR反应体系的优化

目的:以高粱丝黑穗病2381(抗病)、矮四(感病)为材料,以优化SSR反应体系为 目的.方法:采用CTAB法提取高粱基因组总DNA,用SSR分子标记技术对其进行多态性扩增, 通过对体系中不同的Taq酶浓度、模板浓度、dNTP浓度和引物浓度的梯度分析. 结果:建立 并优化了的SSR-PCR反应体系为20ìl反应体系:dNTP浓度为200ìmol/L、Taq酶浓度为1.5U 、 DNA浓度为100ng和引物浓度为0.4ìmol/L.达到了较理想的扩增效果.用该体系对94对SSR 引 物进行了筛选,其中47对引物扩增出了多态性谱带,其中Xtxp3和Xtxp13在抗感的品种间扩 增出了差异谱带.结论:应用优化的SSR反应体系可以对高粱丝黑穗病基因进行分析.     

Influence of Potassium Bromate on Some Malting Properties of Nigerian Sorghum (Sorghum bicolor)

The effect of various concentrations of potassium bromate (a malting additive) was studied on malting sorghum. Potassium bromate at concentrations of 50-125 mg/litre sprinkled on germinating sorghum (28°C ± 1°C) at steep out increased the filtration rate and cold and hot extract values after four days of germination. There was no significant decrease in malting loss at the low concentrations (50-125 mg/litre) of the additive. A higher dose, of 150 mg/litre, decreased the malting loss, while at a concentration of 125 mg/litre a significant increase was observed for the diastatic power after four days of germination.     

High Throughput BAC DNA Isolation for Physical Map Construction of Sorghum (Sorghum bicolor)

With the aim of constructing a physical map of sorghum, we developed a rapid, high throughput approach for isolating BAC DNA suitable for restriction endonuclease digestion fingerprinting, PCR- based STS-content mapping, and BAC-end sequencing. The system utilizes a programmable 96 channel liquid handling system and associated accessories that permit bacterial cultivation and DNA isolation in 96-well plate format. This protocol details culture conditions that optimize bacterial growth in deep-well plates and criteria for BAC DNA isolation to obtain high yields of quality BAC DNA. The system is robust, accurate, and relatively cost-effective. The BAC DNA isolation system has been tested during efforts to construct a physical map of sorghum.     

Seminal Root Growth in Sorghum (Sorghum bicolor) Under Allelopathic Influences from Residues of Taro (Colocasia esculenta)

The length of the seminal root (SR) axis and the number andlength of lateral roots (LRs) of sorghum (Sorghum bicolor Moench)were markedly inhibited by taro [Colocasia esculenta (L.) Schott]residues incorporated into a sand growing medium. The sand profilewas divided equally into zones with and without residues. Productionand elongation of the first-order LRs of the SR axis facingthe zone containing taro residues were severely suppressed.On the side facing the zone that was free of residues, productionand elongation of LRs was not inhibited. SR and LR growth wasdrastically impaired and many plants were killed when taro residueswere incorporated in large amounts into the uppermost 2 cm ofthe growing medium. The activity of the allelopathic substancesin the root zone appeared to be location-specific. Sorghum bicolor, seminal root, lateral root, Colocasia esculenta, taro, taro residues, allelopathic substances, root growth     

DNA polymorphisms in grain sorghum (Sorghum bicolor (L.) Moench)

Molecular markers [random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP)] were used to determine the frequency of DNA polymorphism in grain sorghum (Sorghum bicolor (L.) Moench). Twenty-nine oligonucleotide primers were employed for RAPDs, generating a total of 262 DNA fragments, of which 145 were polymorphic in at least one pairwise comparison between 36 genotypes. Individual primers differed significantly in their ability to detect genetic polymorphism in the species. The overall frequency of polymorphisms was low with a mean frequency of 0.117 polymorphisms per RAPD band being obtained from all pairwise comparisons between genotypes, with maximum and minimum values of 0.212 and 0.039, respectively. Results from phenetic analysis of bandsharing data were consistent with current sub-specific groupings of the species, with clusters of Durra, Zerazera, Caud-Nig, Caud-Kaura and Caffrorum being discernible. The results also indicated that individuals of a similar taxonomic grouping but different geographic origin may be genetically less identical than previously considered. Similar frequencies of polymorphism to that obtained with RAPDs were obtained with RFLPs. Results from these experiments indicated that a high level of genetic uniformity exists within S. bicolor.