Fusarium head blight (FHB) or scab caused by Fusarium species is an economically important disease on small grain cereal crops worldwide. Accurate assessments of the pathogenicity of fungal isolates is a key obstacle toward a better understanding of the Fusarium-wheat scab system. In this study, a new laboratory method for inoculation of wheat coleoptiles was developed, which consists of cutting off the coleoptile apex, covering the cut apex with a piece of filter paper soaked in conidial suspension, and measuring the lengths of brown lesions 7 days post inoculation. After coleoptile inoculation, distinct brown lesions in the diseased stems were observed, in which the presence of the fungus was verified by PCR amplification with F. graminearum Schwable-specific primers. Coleoptile inoculation of six wheat varieties indicated that a highly susceptible wheat variety was more suitable as a differentiating host for the pathogenicity assay. Analysis of the coleoptiles inoculated with a set of 58 different isolates of F. graminearum showed a significant difference in the lengths of the lesions, forming the basis by which pathogenicity of the isolates was assessed. Field inoculation of florets of three wheat varieties over 2 years revealed significant differences in pathogenicity among the 58 isolates, and that the highly resistant and highly susceptible wheat varieties were more appropriate and stable for pathogenicity assessment in field trials. Comparative analyses of eight inoculation experiments of wheat with 58 F. graminearum isolates showed significant direct linear correlations (P<0.001) between coleoptile and floret inoculations. These results indicate that the wheat coleoptile inoculation is a simple, rapid and reliable method for pathogenicity studies of F. graminearum in wheat.

Combined analyses of the natural occurrence of fusarium head blight (FHB), mycotoxins and mycotoxin-producing isolates of Fusarium spp. in fields of wheat revealed FHB epidemics in 12 of 14 regions in Hubei in 2009. Mycotoxin contamination ranged from 0AE59 to 15AE28 lg g )1 in grains. Of the causal agents associated with symptoms of FHB, 84% were Fusarium asiaticum and 9AE5% were Fusarium graminearum, while the remaining 6AE5% were other Fusarium species. Genetic chemotyping demonstrated that F. asiaticum comprised deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-AcDON), 15-acetyldeoxynivalenol (15-AcDON) and nivalenol (NIV) producers, whereas F. graminearum only included DON and 15-AcDON producers. Compared with the chemotype patterns in 1999, there appeared to be a modest shift towards 3-AcDON chemotypes in field populations during the following decade. However, isolates genetically chemotyped as 3-AcDON were present in all regions, whereas the chemical 3-AcDON was only detected in three of the 14 regions where 3-AcDON accounted for 15-20% of the DON and acetylated forms. NIV mycotoxins were detected in seven regions, six of which also yielded NIV chemotypes. The number of genetic 3-AcDON producers was positively correlated with amounts of total mycotoxins (DON, NIV and acetylated forms) or DON in wheat grains. Chemical analyses of wheat grains and rice cultures inoculated with different isolates from the fields confirmed their genetic chemotypes and revealed a preferential biosynthesis of 3-AcDON and 4-AcNIV in rice. These findings suggest the importance of chemotyping coupled with species identification for improved prediction of mycotoxin contamination in wheat.

In this study, the Arabidopsis thaliana NPR1 (non-expressor of PR genes) gene was integrated into an elite wheat cultivar, and the response of the transgenic wheat expressing NPR1 to inoculation with Fusarium asiaticum was analysed. With seedling inoculation, the transgenic lines showed significantly increased fusarium seedling blight (FSB) susceptibility, whereas floret inoculation resulted in enhanced fusarium head blight (FHB) resistance. Quantitative real-time PCR revealed that expression of two defence genes, PR3 and PR5, was associated with susceptible reactions to FSB and FHB, whereas the PR1 gene was activated in resistance responses. This inverse modulation by the constitutively expressed NPR1 gene suggests that NPR1 has a bifunctional role in regulating defence responses in plants. Therefore, it is unsuitable for improving overall resistance to FSB and FHB in wheat.

Dimocarpus longan L., commonly known as longan, is a tropieal fruit tree of the Sapindaeeae family. From 2008 to 2010, a disease survey for longan was eondueted in March and Oetober in Puerto Rico. Fruit rot and inflorescence blight (rotting of the raehis, raehilla, and flowers) were observed in fields of longan at the USDA-ARS Researeh Farm in Isabela, and two eommereial orehards in Puerto Rieo. Tissue seetions (1 mm^) of diseased inflorescences and surface of the fruit were disinfested with 70% ethanol, rinsed with sterile water, and transferred to aeidified potato dextrose agar (APDA). Three isolates of ÍMsiodiplodia theobromae (Pat.) Griffon & Maubl. (Lt) were isolated from symptomatic tissue and identified morpho-moleeularly using a taxonomie key for the Botryosphaeriaeeae and DNA sequenee analysis (1). In APDA, eolonies of ¿i had initial greenish-gray aerial myeelia that turned dark brown with age. Pycnidia were dark brown to black. Immature conidia were sub-ovoid to ellipsoid, apex rounded, truncate at the base, thiek-walled, hyaline, and one-eelled, becoming dark brown, two-celled, and with irregular longitudinal striations when mature. Conidia (n = 50) for all the isolates averaged 26.9 jim long by 13 |im wide. For moleeular identification, the ITS1-5.8S-ITS2 region and fragments of the ß-tubulin and elongation factor 1-alpha (EFla) genes were sequeneed and BLASTn searches done in GenBank. Accession numbers of gene sequences of Lt submitted to GenBank were KC964546, KC964547, and KC964548 for ITS region; KC964549, KC964550. and KC964551 for ß-tubulin; and KC964552, KC964553, and KC964554 for EFl-a. For all genes used, sequences were 99 to 100% identieal to reference isolate CBS 164.96 of Lt reported in GenBank (aeeessions AY640255, EU673110, and AY640258). Pathogenieity tests were eondueted on six random healthy non-detaehed infloreseences of longan and six healthy detached fruits per isolate. Unwounded infloreseenees and fruit were inoculated with 5-mm myeelial disks from 8-day-old pure cultures grown in APDA. Inflorescences were enclosed in plastic bags for 5 days under field eonditions while fruits were kept in a humid chamber using plastic boxes for 5 days under laboratory eonditions of 25°C and 12 h of fluoreseent light. Untreated eontrols were inoeulated with APDA disks only. The experiment was repeated onee. Five days after inoeulation, isolates of Lt eaused infloreseenee blight, fruit rot, and aril (flesh) rot. Infloreseenees turned brown and flower mummifieation was observed on the infloreseenees. The exoearp (peel) and endoearp (aril) turned dark brown and mycelial growth and pyenidia of Lt were observed on fruits. Untreated eontrols did not show any symptoms and no fungi were re-isolated from tissue. In diseased infloreseenees and fruits, Lt was re-isolated from diseased tissue and identified using morphologieal and molecular parameters, thus fulfilling Koch's postulates. Lt has been reported to cause diebaek, stem end rot, and fruit rot on a wide range of plants host (2,4). In longan, Lt has...