In 14 DAI samples, all inoculated roots had typical symptoms. In the root samples from resistant lines, the CFU values ranged from 260.8 ± 22.8 to 527.8, and the CFUs of the basal stems ranged

from 125.0 ± 9.1 to 573.3 ± 28.3. The CFU values for root samples of susceptible lines ranged from 1146.4 ± 13.7 BIBW2992 to 3826.9 ± 455.6 and from 1158.3 ± 24.7 to 6134.2 ± 646.4, respectively, and were significantly greater than those for the resistant lines (Fig. 3). The toxin FB1 was not detected in any of the mock-inoculated roots at any time. Accumulation of FB1 in DsRed-labeled fungus-inoculated root samples was not detected until 48 HAI. No statistically significant difference was observed in the titers of FB1 until 96 HAI (data not shown). At 144 HAI, accumulations of FB1 in the susceptible lines ranged from 11.5 ± 0.3 to 38.4 ± 1.1 ng mL− 1 (Fig. 4). The titer of FB1 in line P138 was significantly

greater than the other lines. In the resistant lines, the concentrations of FB1 remained at low levels with a range of 1.74 ± 0.08 to 5.0 ± 0.46 ng mL− 1, significantly lower than those of the susceptible lines Selleck Crizotinib (P < 0.05). To determine the relationship between the production of FB1 and amount of F. verticillioides colonization, CFUs of maize roots were measured at 144 HAI. All CFU values in the susceptible lines were higher than those of the resistant lines ( Fig. 5). Correlation analysis indicated that the accumulation of FB1 was associated with CFU value (R2 = 0.8095, P < 0.0001). To determine if biosynthesis of FB1 might be influenced by pH or amylopectin content, root samples were collected from susceptible and resistant genotypes at 144 HAI, ground and suspended in distilled water. The pH of roots ranged from 6.0 to 6.3 with no significant difference between susceptible and resistant lines, despite variation among individual lines (Fig. 6). The amounts of amylopectin in roots were also measured, but

the amounts in all the samples were below the limit of detection (data not shown). Infection Tryptophan synthase and systemic colonization of maize by F. verticillioides can occur in different parts of the plants, such as roots, crowns, stalks, and ears, and have been studied using different methods [7], [9], [36] and [37]. However, F. verticillioides, as well as the other kernel rot pathogens, do not form penetration structures, such as appressoria [8] and [38]. There might be a mechanism for the passive movement of conidia along the surface of tissues, allowing the pathogen to get access to an infection court [9]. In the present study, infection and colonization by DsRed-labeled F. verticillioides in maize were examined on maize lines with different reactions to the fungus. The roots of resistant lines showed limited surface growth of F. verticillioides compared to susceptible lines. In the initial stages of infection, F.