This paper describes a reproducible method for the induction of in vitro potato tubers in a wide range of genotypes. These in vitro tubers could be induced in all genotypes tested and show striking similarity to field produced tubers. In vitro tubers may prove most useful as material for International germplasm distribution.

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.

A 2004-2005 survey of potatoes from stores in the north-central potato-producing region of the USA showed that the predominant causes of dry rot were Fusarium graminearum and Fusarium sambucinum. Isolates of F. graminearum originally isolated from potato tubers with dry rot (n = 15), wheat kernels with scab (n = 15), and sugarbeet tap roots with decay (n = 5) were tested for aggressiveness to potato tubers. There were no significant differences in aggressiveness among isolates of F. graminearum, regardless of original host, as measured by their ability to cause dry rot. These findings may have implications for survival of F. graminearum inoculum since potatoes, wheat and sugarbeets are frequently used in crop rotation in the region. Fusarium graminearum required larger wounds for infection of potato tubers than F. sambucinum. Plugremoval injury, simulating a stolon-removal injury, resulted in equal incidence of dry rot caused by the two Fusarium species, whereas abrasion and bruising injury were sufficient for infection and dry rot development by F. sambucinum, but not F. graminearum. A change in harvest practices from vine-killing prior to harvest to mechanical vine-killing on the day of harvest may be a factor affecting the onset of dry rot caused by F. graminearum, since this process often causes large wounds at the stem end of the tubers when the stolon is forcibly removed.

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. 1998. Whole-body protein synthesis in growing barrows: diurnal and dayto-day variation and the effect of site of tracer infusion and sampling. Can. J. Anim. Sci. 78: 575-585. In the first experiment, two catheters were placed in one of three sites for infusion and sampling (vena cava and vena cava with 7 cm between catheter tips, VC/VC, n = 5; right ventricle and atrium, RV/RA, n = 5; anterior aorta and left ventricle, AA/LV, n = 4) to determine the effect of site on the measurement of CO 2 and leucine kinetics. Pigs received a 6-h continuous i.v. infusion of NaH 13 CO 3 (1.45 µmol h -1 kg -1 , preceded by a priming dose of 2.05 µmol kg -1 ) and of L[1-13 C]leucine (9.7 µmol h -1 kg -1 , preceded by a priming dose of 9.7 µmol kg -1 ), the following day. No effect (P > 0.10) of site was observed on NaH 13 CO 3 recovery rate, leucine irreversible loss rate (leucine ILR) and leucine used for protein synthesis (LS). A tendency (P < 0.10) for increased leucine oxidation (LO) was observed with the VC/VC compared to the RV/RA sites. In the second experiment, six growing barrows with catheters in the VC/VC site were infused as earlier with NaH 13 CO 3 and L[1-13 C]leucine for three different 6h periods (12:00 to 18:00 h, first day; 20:00 to 02:00 h, night; 12:00 to 18:00 h, second day) to determine the diurnal and day-to-day variation of CO 2 and leucine kinetics. No effect (P > 0.10) of period was observed on NaH 13 CO 3 recovery rate, leucine ILR and LS. The LO was lower (P < 0.05) on the second day compared with the first day (day-to-day variation) while similar (P > 0.10) LO was observed between the first day and night (diurnal variation). Together, these results indicate that 1) the VC/VC site can be used for L[1-13 C]leucine and NaH 13 CO 3 infusions, 2) NaH 13 CO 3 recovery studies can be performed either the day preceding or following the measurement of substrate and 3) protein synthesis estimated from a 6-h infusion period can be extrapolated to the 24 h periods under conditions of frequent feeding.Key words: Pigs, leucine, protein synthesis, tracer techniques, diurnal variation Roy, N., Lapierre, H., Estrada, R. et Bernier, J. F. 1998. Synthèse protéique de l'organisme entier chez les porcs en croissance: variation diurne, quotidienne et l'effet de sites d'infusion et de prélèvement du traceur. Can. J. Anim. Sci. 78: 575-585. Dans la première expérience, deux cathéters ont été placés dans un des sites sélectionnés (veine cave et veine cave avec 7 cm entre les extrémités des cathéters, VC/VC, n = 5; ventricule et oreillette droits, RV/RA, n = 5; aorte antérieure et ventricule gauche, AA/LV, n = 4) pour vérifier l'effet du site de perfusion et de prélèvement sur les cinétiques du CO 2 et de la leucine. Les porcs ont été perfusés i.v. durant 6 h avec du NaH 13 CO 3 (1,45 µmol h -1 kg -1 , précédé d'une dose d'amorçage de 2,05 µmol kg -1 ) et avec de la L-[1-13 C] leucine (9,7 µmol h -1 kg -1 , précédé d'une dose d'amorçage de 9,7 µmol kg -1 ), le lendemain. Aucun effet (P > 0,10) des sites n'a été observé sur l...