Barley traits associated with resistance to fusarium head blight and deoxynivalenol accumulation

ABSTRACT Fusarium head blight (FHB) or scab is a destructive disease of barley in many countries. A better understanding of the interrelationships between plant traits and FHB resistance should help in the development of effective and efficient breeding strategies for FHB-resistant cultivars. Recent mapping studies indicate that many of the quantitative trait loci (QTL) for FHB resistance coincide with the QTL for plant height, heading date, and spike characteristics. Therefore, a study was conducted to investigate the relationship of morphological and physiological traits to FHB infection and deoxynivalenol (DON) accumulation in a barley doubled-haploid (DH) population derived from a Léger x CI9831 cross. Approximately 190 DH lines were grown at Ottawa (Ontario) for 2 years, Charlottetown (Prince Edward Island) for 1 year, and Hangzhou (Zhejiang) for 2 years. The field plots were inoculated with Fusarium graminearum at each location. FHB incidence was positively correlated with DON content. Resistance to FHB was associated with two-row spike, purple lemma, long glume awn, tall stature, and resistance to lodging, but it was not associated with long rachilla hairs, rough lemma awn, or heading date. Two-row spike was associated with tall stature and resistance to lodging. These associations as well as its spike characteristics helped reduce FHB infection and DON accumulation in two-row lines compared with six-row lines. The association between long glume awn and FHB resistance could be due to genetic linkages. Therefore, trait associations should be taken into consideration when breeding for FHB resistance and interpreting data from FHB experiments.     

Quantitative trait loci for Fusarium head blight resistance in a recombinant inbred population of Wangshuibai/Wheaton

Use of diverse sources of Fusarium head blight (FHB)-resistant germplasm in breeding may significantly improve wheat resistance to FHB. Wangshuibai is an FHB-resistant Chinese landrace unrelated to cv. Sumai 3, the most commonly used FHB-resistant source. In all, 139 F(6) recombinant inbred lines were developed from a cross between Wangshuibai and an FHB-susceptible cultivar, Wheaton, to map quantitative trait loci (QTL) for wheat resistance to initial infection (type I resistance), spread of FHB symptoms within a spike (type II resistance), and deoxynivalenol (DON) accumulation (type III resistance) in infected grain. The experiments were conducted in a greenhouse at Manhattan, KS from 2003 to 2005. More than 1,300 simple-sequence repeat and amplified fragment length polymorphism markers were analyzed in this population. Five QTL for type I resistance were detected on chromosomes 3AS, 3BS, 4B, 5AS, and 5DL after spray inoculation; seven QTL for type II resistance were identified on chromosomes 1A, 3BS, 3DL, 5AS, 5DL, and 7AL after point inoculation; and seven QTL for type III resistance were detected on chromosomes 1A, 1BL, 3BS, 5AS, 5DL, and 7AL with the data from both inoculation methods. These QTL jointly explained up to 31.7, 64, and 52.8% of the phenotypic variation for the three types of FHB resistance, respectively. The narrow-sense heritabilities were low for type I resistance (0.37 to 0.41) but moderately high for type II resistance (0.45 to 0.61) and type III resistance (0.44 to 0.67). The QTL on the distal end of 3BS, 5AS, and 5DL contributed to all three types of resistance. Two QTL, on 7AL and 1A, as well as one QTL near the centromere of 3BS (3BSc), showed effects on both type II and type III resistance. Selection for type II resistance may simultaneously improve type I and type III resistance as well. The QTL for FHB resistance identified in Wangshuibai have potential to be used to pyramid FHB-resistance QTL from different sources.     

Silicon amendment improves wheat defence against Fusarium graminearum and complements the control by fungicide of Fusarium head blight

A three-year field experiment with two wheat cultivars evaluated the effect of soil-applied silicon (Si), with and without fungicide spraying, on Fusarium head blight (FHB) control. Silicon treatment alone reduced FHB severity and the percentage of damaged wheat kernels, regardless of the cultivar. The best disease control was obtained for the cultivar with moderate disease resistance (MR), supplied with silicon and treated with fungicide during flowering. Silicon treatment alone promoted an increase in deoxynivalenol (DON) concentration in the disease-susceptible cultivar; however, in the MR cultivar, silicon amendment associated with fungicide treatment led to a reduction in DON concentration. Greenhouse experiments evaluated the effect of silicon combined with different timings of fungicide application on wheat defences against Fusarium graminearum. Plants supplied with silicon had a longer pathogen incubation period, lower FHB severity and lower DON concentration when compared to plants without silicon. In addition, silicon-supplied plants had higher soluble phenolic content and altered antioxidant enzyme activities (SOD, CAT, POX and PPO) that favoured early accumulation of hydrogen peroxide when compared to plants without silicon. Greater control of FHB and lower DON concentration in plants treated with silicon and fungicide before inoculation and up to 1 day after inoculation was associated with increased levels of defence-associated metabolites. Silicon contributed to the reduction of FHB and DON concentration in wheat, especially for the MR cultivar and, when combined with fungicide spraying, both MR and disease-susceptible cultivars had enhanced performances upon silicon amendment.     

Mapping of quantitative trait Loci for fusarium head blight resistance in barley

ABSTRACT Fusarium head blight (FHB) is a devastating disease that causes significant reductions in yield and quality in wheat and barley. Barley grains infected with deoxynivalenol (DON), a vomitoxin produced by Fusarium graminearum, are rejected for malting and brewing. Among six-rowed barley cultivars tested thus far, only cv. Chevron exhibited resistance. This study was conducted to map genes and to identify DNA markers for marker-assisted breeding for FHB resistance in cv. Chevron with restriction fragment length polymorphism (RFLP) markers. A doubled haploid (DH) population was created from a cross between cv. Chevron and susceptible cv. Stander. Seven field experiments were conducted in four different locations in 2 years. A RFLP map containing 211 loci and covering over 1,000 centimorgans (cM) of the genome was used to map quantitative trait loci (QTL) associated with relatively low FHB severity and DON concentration. Morphological traits differing between the parents were also measured: heading date, plant height, spike angle, number of nodes per cm of rachis in the spike, and kernel plumpness. Many of the QTL for FHB and DON coincided with QTLs for these morphological traits. The "fix-QTL" algorithm in Mapmaker QTL was used to remove the part of the variance for FHB resistance that may be explained by heading date or plant height. Results from this study suggest that QTLs with major effects for FHB resistance probably do not exist in cv. Chevron. Three QTL intervals, Xcmwg706-Xbcd441 on chromosome 1H, Xbcd307b-Xcdo684b on chromosome 2H, and Xcdo959b-Xabg472 on chromosome 4H, that are not associated with late heading or height may be useful for marker-assisted selection.     

Quantitative trait loci for resistance to fusarium head blight and deoxynivalenol accumulation in Wangshuibai wheat under field conditions

Wangshuibai is a Chinese landrace wheat with a high level of resistance to fusarium head blight (FHB) and deoxynivalenol (DON) accumulation. Using an F7 population of recombinant inbred lines (RILs) derived from the cross between Wangshuibai and Annong 8455 for molecular mapping of quantitative trait loci (QTL) for FHB resistance, the proportion of scabbed spikelets (PSS) and DON content were assessed under field conditions. Composite interval mapping revealed that two and three QTL were significantly associated with low PSS and low DON content, respectively, over 2 years. QTL on chromosomes 3B and 2A explained 17 and 11·5%, respectively, of the phenotypic variance for low PSS, whereas QTL on chromosomes 5A, 2A and 3B explained 12·4, 8·5 and 6·2%, respectively, of the phenotypic variance for low DON content. The 3B QTL appeared to be associated mainly with low PSS, and the 5A QTL primarily with low DON content in Wangshuibai. The 2A QTL had minor effects on both low PSS and DON content. Microsatellite and AFLP markers linked to these QTL should be useful for marker-assisted selection of QTL for low PSS and low DNA content from Wangshuibai.     

Identification and characterization of international Fusarium head blight screening nurseries of wheat at CIMMYT, Mexico

Fusarium head blight (FHB) is a major threat to wheat production globally, causing not only yield losses but also food and feed contamination. FHB research began at the International Maize and Wheat Improvement Center (CIMMYT) in the early 1980’s, and since then, large-scale FHB screening has been conducted to identify and incorporate new resistance genes into elite CIMMYT germplasm. Promising lines with good FHB resistance were regularly compiled as a Fusarium Head Blight Screening Nursery (FHBSN) and distributed worldwide. The first FHBSN was assembled in 1985, and the most recent two were the 13th and 14th FHBSN that were released in 2011 and 2012, respectively. Candidate lines for a FHBSN came mainly from different CIMMYT wheat breeding programs and were tested for three consecutive years before being included in an FHBSN. FHBSN screening was conducted under strictly standardized field conditions at El Batán, where CIMMYT headquarters is located, using artificial inoculation of F. graminearum strains, whose aggressiveness and DON chemotypes had been previously identified. FHB index was scored at 31 days after inoculation for all lines and DON concentration was measured only for elite lines in their 2nd and 3rd year of evaluation. Haplotyping is a new tool for genetic characterization of FHBSN entries and helps to identify new resistance sources with novel resistance genes and to better target crosses toward diversifying and/or pyramiding resistance. The 13th FHBSN was taken as an example in this paper to show the procedure and strategy for the development of new FHB resistant lines.     

Effect of infection timing on fusarium head blight and mycotoxin accumulation in open- and closed-flowering barley

ABSTRACT Barley has two flowering types, chasmogamous (open-flowering) and cleistogamous (closed-flowering). We examined the effect of the timing of Fusarium graminearum infection on Fusarium head blight (FHB) and mycotoxin accumulation in barley cultivars with different flowering types using greenhouse experiments. In the first experiment, 13 cultivars were spray inoculated at two different developmental stages, and the severity of FHB was evaluated. The effect of the timing of infection differed among cultivars. Cleistogamous cultivars were resistant at anthesis but susceptible at 10 days after anthesis, whereas chasmogamous cultivars were already susceptible at anthesis. In the second experiment, five cultivars were inoculated at three different developmental stages and the concentrations of deoxynivalenol (DON) and nivalenol (NIV) in mature grain were analyzed. Cleistogamous cultivars accumulated more mycotoxins (DON and NIV) when inoculated 10 or 20 days after anthesis than when inoculated at anthesis, whereas chasmogamous cultivars accumulated more mycotoxins when inoculated at anthesis. Thus, the most critical time for F. graminearum infection and mycotoxin accumulation in barley differs with cultivar, and likely is associated with the flowering type. Late infection, even without accompanied FHB symptoms, was also significant in terms of the risk of mycotoxin contamination.     

Effect of nitrogen application at anthesis on Fusarium head blight and mycotoxin accumulation in breadmaking wheat in the western part of Japan

In the western part of Japan, two wheat cultivars, Nishinokaori and Minaminokaori, are currently cultivated for breadmaking. Breadmaking wheat requires a higher protein content compared to the Japanese noodle wheat (the major type of wheat in Japan). This high protein level in the grain is obtained by top-dressing with nitrogen (N) near anthesis. Because such N applications may increase levels of Fusarium head blight (FHB) and consequent mycotoxin [deoxynivalenol (DON) and nivalenol (NIV)] accumulation in the grain, the effect of N application (0, 4, and 8 g/m²) at anthesis on FHB and mycotoxin accumulation in Nishinokaori and Minaminokaori was tested in the greenhouse in 2004 and 2005 and in two fields in 2006. In the greenhouse, plants were spray inoculated at 3, 10, and 20 days after N treatment. In field experiments, colonized maize kernels, which generate ascospores during the testing season, served as inoculum. In all experiments for both cultivars, N application at anthesis significantly increased grain protein as expected, but had no significant effect on FHB and DON and NIV levels in grain. These results suggest that, at least in these cultivars, N can be applied close to anthesis without increasing the risk of FHB and mycotoxin (DON and NIV) accumulation.     

The Effect of Inoculation Treatment and Long-term Application of Moisture on Fusarium Head Blight Symptoms and Deoxynivalenol Contamination in Wheat Grains

Fusarium head blight (FHB) is an important disease of wheat, which can result in the contamination of grains with mycotoxins such as deoxynivalenol (DON). Artificial inoculation of flowering ears with conidial suspensions is widely used to study FHB diseases. Our goal was to compare four inoculation treatments in which a conidial suspension was sprayed on flowering ears and to study the effect of the application of moisture during kernel setting and filling with a mist-irrigation system. Ten wheat genotypes were inoculated with a DON-producing Fusarium culmorum strain. Inoculation treatments varied in time of application of the inoculum (morning or evening) and in the method of controlling humidity during inoculation (bagging or mist irrigation). A wet season was simulated with a mist-irrigation system, keeping the crop canopy wet for at least 26 days after flowering. The severity of FHB symptoms (area under disease progress curve (AUDPC)), yield loss and DON contamination in the grains were determined. AUDPC data obtained with the different inoculation treatments were highly correlated (r=0.85–0.95). Mist irrigation after inoculation resulted in a higher mean disease severity, but in a overall lower toxin contamination as compared to the non-irrigated treatments. Genotypic differences in DON accumulation were present: for one wheat line toxin contamination significantly increased when irrigated, while two genotypes accumulated significantly less toxin. The closest relationships (r=0.73–0.89) between the visual symptoms and the DON content were obtained under moderate mean infection pressure. This relation between visual symptoms and the DON content deteriorated at higher infection levels.     

Maize maturity and the development of gibberella ear rot symptoms and deoxynivalenol after inoculation

Development of gibberella ear rot disease symptoms and the accumulation of the mycotoxin deoxynivalenol (DON) in maize ears inoculated via the silk with Fusarium graminearum was determined at various times after inoculation. Ten hybrids ranging in maturity from early to late, were inoculated with a conidial suspension in 1993 and 1994 and harvested every 2 weeks for 14 weeks after inoculation. Disease symptom evaluations were conducted on all 10 hybrids; five of these hybrids were further analysed for DON concentrations. Disease symptoms reached a maximum and stabilized by 6 weeks after inoculation, approximately at physiological maturity (35% kernel moisture) for the early hybrids and the late dent stage of maturity for later hybrids. Deoxynivalenol accumulation was correlated with symptom development but did not stabilize at 6 weeks for all genotypes. Hybrid maturity did not influence symptom development or DON accumulation, but environment did. For the evaluation of hybrids, assessments of resistance to fungal invasion and mycotoxin accumulation based on symptom development could be made much earlier than the current 12-14 week harvest time commonly used in inoculated experiments.     

小麦不同生育期施用丙硫菌唑及施用次数对小麦赤霉病及籽粒DON毒素的控制效果

为探明在小麦不同生育期施用新型杀菌剂丙硫菌唑及施用次数对小麦赤霉病及籽粒DON毒素总量[包括脱氧雪腐镰刀菌烯醇(DON)?3-乙酰脱氧雪腐镰刀菌烯醇(3-ADON)?15-乙酰脱氧雪腐镰刀菌烯醇(15-ADON)]的控制效果, 2020年-2021年通过田间自然发病和人工接种发病试验的方法, 研究了小麦不同生育期施用丙硫菌唑及施用次数对小麦赤霉病的防效, 并通过液相色谱-串联质谱法测定了不同处理小麦籽粒中对DON毒素总含量?结果表明, 30%丙硫菌唑可分散油悬浮剂(OD)防治2次对小麦赤霉病的防效和对DON毒素的控制效果均显著高于防治1次; 防治2次时, 其首次最佳防治时期为小麦齐穗期至扬花20%, 防效为90.25%~95.13%, 毒素控制效果为77.35%~79.97%?30%丙硫菌唑OD作为防控小麦赤霉病的新型药剂具有良好的应用前景, 本研究为该药剂推广应用于小麦赤霉病及籽粒DON毒素的防控提供了科学依据?     

不同小麦品种(系)对赤霉病的抗性和麦穗组织中DON毒素积累分析

 为明确不同小麦品种(系)对赤霉病的抗性和麦穗组织中DON毒素积累水平,培育和利用抗赤霉病和DON毒素积累的品种提供资源和依据,本研究采用单小花滴注接种法对河南省的106个小麦品种(系)抗赤霉病性进行鉴定分析,并用ELISA测定了病穗组织中DON毒素水平。结果表明不同小麦品种(系)对赤霉病的抗性有显著差异,106个小麦品种(系)中未发现抗病和中抗材料,中感品种(系)有华育198、郑麦103和春丰0021等14个,占13.2%;感病的有曌式2010-06、百农898和中麦63等92个,占86.8%。不同小麦品种(系)籽粒、颖壳和穗轴中DON毒素积累水平有显著差异,籽粒中DON毒素水平在(0.70~287.63)mg/kg之间,其中郑03876、豫保1号和中麦63 的DON毒素水平在2 mg/kg 以下,为抗毒素材料;其他的103个品种DON毒素水平大于2 mg/kg;颖壳和穗轴中的DON毒素水平在(51.03~392.87)mg/kg之间,普遍比籽粒中DON毒素含量高。籽粒中DON毒素水平与小麦品种(系)的平均病害严重度间呈极显著正相关。     

The Brachypodium distachyon UGT Bradi5gUGT03300 confers type II fusarium head blight resistance in wheat

Fusarium head blight (FHB), caused by fungi belonging to the Fusarium genus, is a widespread disease of wheat (Triticum aestivum) and other small-grain cereal crops. The main causal agent of FHB, Fusarium graminearum, produces mycotoxins mainly belonging to type B trichothecenes, such as deoxynivalenol (DON), that can negatively affect humans, animals and plants. DON detoxification, mainly through glucosylation into DON-3-O-glucose, has been correlated with resistance to FHB. A UDP-glucosyltransferase from the model cereal species Brachypodium distachyon has been shown to confer resistance both to initial infection and to spike colonization (type I and type II resistances, respectively). Here, the functional characterization of transgenic wheat lines expressing the Bradi5g03300 UGT gene are described. The results show that, following inoculation with the fungal pathogen, these lines exhibit a high level of type II resistance and a strong reduction of mycotoxin content. In contrast, type I resistance was only weakly observed, although previously seen in B. distachyon, suggesting the involvement of additional host-specific characteristics in type I resistance. This study contributes to the understanding of the functional relationship between DON glucosylation and FHB resistance in wheat.     

Real-time PCR Quantification and Mycotoxin Production of Fusarium graminearum in Wheat Inoculated with Isolates Collected from Potato, Sugar Beet, and Wheat

ABSTRACT Fusarium graminearum causes Fusarium head blight (FHB) in small grains worldwide. Although primarily a pathogen of cereals, it also can infect noncereal crops such as potato and sugar beet in the United States. We used a real-time polymerase chain reaction (PCR) method based on intergenic sequences specific to the trichodiene synthase gene (Tri5) from F. graminearum. TaqMan probe and primers were designed and used to estimate DNA content of the pathogen (FgDNA) in the susceptible wheat cv. Grandin after inoculation with the 21 isolates of F. graminearum collected from potato, sugar beet, and wheat. The presence of nine mycotoxins was analyzed in the inoculated wheat heads by gas chromatography and mass spectrometry. All isolates contained the Tri5 gene and were virulent to cv. Grandin. Isolates of F. graminearum differed significantly in virulence (expressed as disease severity), FgDNA content, and mycotoxin accumulation. Potato isolates showed greater variability in producing different mycotoxins than sugar beet and wheat isolates. Correlation analysis showed a significant (P < 0.001) positive relationship between FgDNA content and FHB severity or deoxynivalenol (DON) production. Moreover, a significant (P < 0.001) positive correlation between FHB severity and DON content was observed. Our findings revealed that F. graminearum causing potato dry rot and sugar beet decay could be potential sources of inoculum for FHB epidemics in wheat. Real-time PCR assay provides sensitive and accurate quantification of F. graminearum in wheat and can be useful for monitoring the colonization of wheat grains by F. graminearum in controlled environments, and evaluating wheat germplasms for resistance to FHB.     

Evaluation and characterization of resistance to fusarium head blight caused by Fusarium culmorum in UK winter wheat cultivars

Fusarium head blight (FHB) resistance of 50 cultivars from the National List of winter wheat cultivars approved for sale (or were undergoing trails for approval in 2003) in the UK was compared with 21 reference cultivars from continental Europe which had previously been characterized for resistance. Only three UK National List cultivars (Soissons, Spark and Vector) had stable resistance over trial sites that was significantly greater than that of the FHB susceptible cultivar Wizard. In addition, under moderate disease pressure, 21 of the National List cultivars had levels of the trichothecene mycotoxin deoxynivalenol (DON) above the proposed European Union limit of 1·25 ppm in grain. Surveys show that levels of FHB and DON in the UK crop are currently very low, however, should disease pressure increase for any reason, then an improvement in the overall levels of FHB resistance of UK winter wheat germplasm will be required. In order to infer the origin of resistance and to identify potentially novel resistance, allele sizes of microsatellite (simple sequence repeat, SSR) markers linked to quantitative trait loci (QTL) for FHB resistance were compared between the test cultivars and known, characterized resistance sources. The major FHB resistance QTL from the Chinese cv. Sumai-3 (3BS, 5A and 6B), the Romanian cv. Fundulea F201R (1B and 5A) and the French cv. Renan (5AL) were screened with 17 SSRs. No National List cultivar had haplotypes similar to any of these QTL. However, the highly resistant German reference cultivar Petrus had an identical haplotype to cv. Fundulea F201R on 1B indicating that this cultivar has an allelic FHB resistance QTL at that location.     

Selection for quantitative trait loci associated with resistance to Stewart's wilt in sweet corn

The objectives of this research were to identify quantitative trait loci (QTL) for Stewart's wilt resistance from a mapping population derived from a sweet corn hybrid that is highly resistant to Pantoea stewartii and to determine if marker-based selection for those QTL could substantially improve Stewart's wilt resistance in a population derived from a cross of resistant lines and a highly susceptible sweet corn inbred. Three significant QTL for Stewart's wilt resistance on chromosomes 2 (bin 2.03), 5 (bin 5.03), and 6 (bin 6.06/6.07) explained 31% of the genetic variance in a population of 110 F(3:4) families derived from the sweet corn hybrid Bonus. The three QTL appeared to be additive in their effects on Stewart's wilt ratings. Based on means of families that were either homozygous or heterozygous for marker alleles associated with the resistance QTL, the QTL on chromosomes 2 and 6 appeared to have dominant or partially dominant gene action, while the QTL on chromosome 5 appeared to be recessive. A population of 422 BC(2)S(2) families was derived from crosses of a sweet corn inbred highly susceptible to Stewart's wilt, Green Giant Code 88 (GG88), and plants from two F(3:4) families (12465 and 12467) from the Bonus mapping population that were homozygous for marker alleles associated with Stewart's wilt resistance at the three QTL. Mean Stewart's wilt ratings for BC(2)S(2) families were significantly (P < 0.05) lower for families that were homozygous for the bnlg1902 marker allele (bin 5.03) from resistant lines 12465 or 12467 than for families that were heterozygous at this marker locus or homozygous for the bnlg1902 marker allele from GG88. Resistance associated with this QTL was expressed only if F(3:5) or BC(2)S(2) families were homozygous for marker alleles associated with the resistant inbred parent (P(1)). Marker alleles identified in the F(3:5) mapping population that were in proximity to the resistance QTL on chromosomes 2 and 6 were not polymorphic in crosses of GG88 with 12465 and 12467. Selection for other polymorphic marker loci adjacent to these two regions did not improve Stewart's wilt resistance of BC(2)S(2) families.     

Evaluation of type I fusarium head blight resistance of wheat using non-deoxynivalenol-producing fungi

A series of experiments was conducted to determine whether type I resistance (resistance to initial infection) to fusarium head blight (FHB) in wheat could be assessed using fungal species/isolates that do not produce deoxynivalenol (DON), a mycotoxin critical to the spread of Fusarium graminearum in the wheat spike. It was shown that, while the non-toxin-producing species Microdochium nivale and M. majus could infect following spray inoculation of wheat spikes, they were unable to spread within the spike following point inoculation. However, although these species might reveal type I resistance, they are not highly pathogenic towards wheat. A nivalenol (NIV)-producing isolate of F. graminearum caused high levels of disease following spray inoculation, but spread only very slowly within the spike and rarely induced bleaching above the point of inoculation. It is proposed that spray inoculation with an appropriate, aggressive, non-DON-producing FHB pathogen may be used to characterize type I resistance to complement point inoculation with a DON-producing isolate to assess type II resistance (resistance to spread within the spike).     

Fusarium head blight evaluation in wheat transgenic plants expressing the maize <Emphasis Type="Italic">b-32</Emphasis> antifungal gene

The maize gene b-32, normally expressed in the maize (Zea mays) endosperm, encodes for a RIP (Ribosome Inactivating Protein) characterised by antifungal activity. Transgenic wheat plants were obtained via biolistic transformation, in which the b-32 gene is driven by the 35SCaMV promoter in association with the bar gene as a selectable marker. Plants were brought to homozygosity through genetic analysis of progeny and pathogenicity tests were performed on the fourth generation. Six homozygous b-32 wheat lines were characterised. All plants had a normal phenotype, not distinguishable from the control cv. Veery except for slightly smaller size, flowered and set seeds. Western blot analyses confirmed b-32 expression during the plant life cycle in the various tissues. Each line differed in the b-32 content in leaf protein extracts and the transgenic protein expression level was maintained at least up to 10 days after anthesis. Pathogenicity tests for Fusarium head blight (FHB) were performed on the b-32 transgenic wheat lines in comparison to the parental cv. Veery. Resistance to FHB was evaluated by the single floret injection inoculation method on immature spikes with spores of Fusarium culmorum. In all the transgenic lines, a similar reduction in FHB symptoms, not dependent on the level of b-32 protein, has been observed (20% and 30% relative to the control, respectively 7 and 14 days after inoculation). Percentage of tombstone kernels at maturity was also recorded; in all transgenic lines disease control for this parameter was around 25%. The data obtained indicate that maize b-32 was effective as in vivo antifungal protein reducing FHB symptoms in wheat lines expressing the maize RIP protein.     

脱氧雪腐镰刀菌烯醇( DON) 在小麦籽粒中的积累分析

 镰刀菌产生的脱氧雪腐镰刀菌烯醇(deoxynivalenol,DON)污染小麦后对人畜具有较大的毒害作用。为明确DON毒素在小麦籽粒中的积累数量及其与镰刀菌菌株、接菌数量、小麦品种和病害严重度的关系,试验采用单花滴注方法在5个抗病性不同的小麦品种上分别接种9 个禾谷镰刀菌菌株,每个菌株接种1 × 106 、1 × 105 和1 × 104 个/ mL 3 个分生孢子浓度,并利用ELISA 法测定收获麦粒中DON 毒素含量。结果表明,麦粒中DON 毒素含量差异主要是由于不同禾谷镰刀菌菌株产生毒素能力不同所致。接种菌株8003、4020 的所有麦粒中DON 毒素含量均显著高于相同条件下接种其他7 个菌株的小麦。当接种产毒素能力强的菌株时,小麦抗病品种表现出在一定程度上降低DON 毒素积累的能力。不同接菌浓度对小麦赤霉病的发病程度和麦粒中DON 毒素含量有显著影响,在相同条件下,接菌浓度越高,病害严重度越高,DON 毒素含量也越高;反之,接菌浓度越低,病害严重度越低,DON 毒素含量也越低。