Kamaranga H. S. Peiris

Effects of Integrating Cultivar Resistance and Fungicide Application on Fusarium Head Blight and Deoxynivalenol in Winter Wheat

Fusarium head blight (FHB) or scab, incited by Fusarium graminearum, can cause significant economic losses in small grain production. Five field experiments were conducted from 2007 to 2009 to determine the effects on FHB and the associated mycotoxin deoxynivalenol (DON) of integrating winter wheat cultivar resistance and fungicide application. Other variables measured were yield and the percentage of Fusarium-damaged kernels (FDK). The fungicides prothioconazole + tebuconazole (formulated as Prosaro 421 SC) were applied at the rate of 0.475 liters/ha, or not applied, to three cultivars (experiments 1 to 3) or six cultivars (experiments 4 and 5) differing in their levels of resistance to FHB and DON accumulation. The effect of cultivar on FHB index was highly significant (P < 0.0001) in all five experiments. Under the highest FHB intensity and no fungicide application, the moderately resistant cultivars Harry, Heyne, Roane, and Truman had less severe FHB than the susceptible cultivars 2137, Jagalene, Overley, and Tomahawk (indices of 30 to 46% and 78 to 99%, respectively). Percent fungicide efficacy in reducing index and DON was greater in moderately resistant than in susceptible cultivars. Yield was negatively correlated with index, with FDK, and with DON, whereas index was positively correlated with FDK and with DON, and FDK and DON were positively correlated. Correlation between index and DON, index and FDK, and FDK and DON was stronger in susceptible than in moderately resistant cultivars, whereas the negative correlation between yield and FDK and yield and DON was stronger in moderately resistant than in susceptible cultivars. Overall, the strongest correlation was between index and DON (0.74 ≤ R ≤ 0.88, P ≤ 0.05). The results from this study indicate that fungicide efficacy in reducing FHB and DON was greater in moderately resistant cultivars than in susceptible ones. This shows that integrating cultivar resistance with fungicide application can be an effective strategy for management of FHB and DON in winter wheat.

NIR absorbance characteristics of deoxynivalenol and of sound and Fusarium -damaged wheat kernels

The near infrared (NIR) absorption spectra of deoxynivalenol (DON) and single wheat kernels with or without DON were examined. The NIR absorption spectra of 0.5–2000 ppm of DON in acetonitrile were recorded in the 350–2500 nm range. Second derivative processing of the NIR spectra and spectral subtractions showed DON absorption bands at 1408 nm, 1904 nm and 1919 nm. NIR spectra of sound and Fusarium-damaged kernels were also acquired using two instruments. Subtraction of average absorption spectra and second derivative spectra were evaluated to identify different NIR signatures of the two types of kernel. Differences in peak height and positions of the NIR absorption bands of the kernels were noted. At 1204 nm, 1365 nm and 1700 nm, the differences were in the heights of the absorption peaks. Such differences may be attributed to changes in the levels of grain food reserves such as starches, proteins and lipids and other structural compounds. Shifts in absorption peak positions between the two types of kernels were observed at 1425–1440 nm and 1915–1930 nm. These differences may arise from other NIR active compounds, such as DON, which are not common for the two types of kernel. Since the NIR absorption of DON may have contributed to the shifts between sound and Fusarium-damaged kernels, this study indicates the potential for NIR spectrometry to evaluate Fusarium damage in single kernels based on the DON levels.

Near-Infrared Spectroscopic Method for Identification of Fusarium Head Blight Damage and Prediction of Deoxynivalenol in Single Wheat Kernels

Cereal Chem. 87(6):511–517 Fusarium Head Blight (FHB), or scab, can result in significant crop yield losses and contaminated grain in wheat (Triticum aestivum L.). Growing less susceptible cultivars is one of the most effective methods for managing FHB and for reducing deoxynivalenol (DON) levels in grain, but breeding programs lack a rapid and objective method for identifying the fungi and toxins. It is important to estimate proportions of sound kernels and Fusarium-damaged kernels (FDK) in grain and to estimate DON levels of FDK to objectively assess the resistance of a cultivar. An automated single kernel near-infrared (SKNIR) spectroscopic method for identification of FDK and for estimating DON levels was evaluated. The SKNIR system classified visually sound and FDK with an accuracy of 98.8 and 99.9%, respectively. The sound fraction had no or very little accumulation of DON. The FDK fraction was sorted into fractions with high or low DON content. The kernels identified as FDK by the SKNIR system had better correlation with other FHB assessment indices such as FHB severity, FHB incidence and kernels/g than visual FDK%. This technique can be successfully employed to nondestructively sort kernels with Fusarium damage and to estimate DON levels of those kernels. Single kernels could be predicted as having low ( 60 ppm) DON with ≈96% accuracy. Single kernel DON levels of the high DON kernels could be estimated with R 2 = 0.87 and standard error of prediction (SEP) of 60.8 ppm. Because the method is nondestructive, seeds may be saved for generation advancement. The automated method is rapid (1 kernel/sec) and sorting grains into several fractions depending on DON levels will provide breeders with more information than techniques that deliver average DON levels from bulk seed samples.

Evaluating RNAlater® as a preservative for using near-infrared spectroscopy to predict Anopheles gambiae age and species

BackgroundMosquito age and species identification is a crucial determinant of the efficacy of vector control programmes. Near-infrared spectroscopy (NIRS) has previously been applied successfully to rapidly, non-destructively, and simultaneously determine the age and species of freshly anesthetized African malaria vectors from the Anopheles gambiae s.l. species complex: An. gambiae s. s. and Anopheles arabiensis. However, this has only been achieved on freshly-collected specimens and future applications will require samples to be preserved between field collections and scanning by NIRS. In this study, a sample preservation method (RNAlater®) was evaluated for mosquito age and species identification by NIRS against scans of fresh samples.MethodsTwo strains of An. gambiae s.s. (CDC and G3) and two strains of An. arabiensis (Dongola, KGB) were reared in the laboratory while the third strain of An. arabiensis (Ifakara) was reared in a semi-field system. All mosquitoes were scanned when fresh and rescanned after preservation in RNAlater® for several weeks. Age and species identification was determined using a cross-validation.ResultsThe mean accuracy obtained for predicting the age of young (<7 days) or old (≥ 7 days) of all fresh (n = 633) and all preserved (n = 691) mosquito samples using the cross-validation technique was 83% and 90%, respectively. For species identification, accuracies were 82% for fresh against 80% for RNAlater® preserved. For both analyses, preserving mosquitoes in RNAlater® was associated with a highly significant reduction in the likelihood of a misclassification of mosquitoes as young or old using NIRS. Important to note is that the costs for preserving mosquito specimens with RNAlater® ranges from 3-13 cents per insect depending on the size of the tube used and the number of specimens pooled in one tube.ConclusionRNAlater® can be used to preserve mosquitoes for subsequent scanning and analysis by NIRS to determine their age and species with minimal costs and with accuracy similar to that achieved from fresh insects. Cold storage availability allows samples to be stored longer than a week after field collection. Further study to develop robust calibrations applicable to other strains from diverse ecological settings is recommended.

Age-grading the biting midge Culicoides sonorensis using near-infrared spectroscopy

Age‐grading of insects is important in the control and monitoring of both insect populations and vector‐borne diseases. Microscopy and morphological techniques exist to age‐grade most blood‐feeding flies, but these techniques are laborious, often destructive to the insects, and slow. Near‐infrared spectroscopy (NIRS) can be automated and is a non‐destructive technique for age‐grading. We applied NIRS techniques to age‐grade females of the biting midge, Culicoides sonorensis Wirth & Jones (Diptera: Ceratopogonidae), the vector of bluetongue and other arboviruses in North America. Female flies of five known age cohorts (1, 3, 6, 9 and 12 days post‐emergence) from three laboratory colonies were used. The data indicate that NIRS can be used to differentiate age groups of C. sonorensis.

Determining Weight and Moisture Properties of Sound and Fusarium-Damaged Single Wheat Kernels by Near-Infrared Spectroscopy

ABSTRACT Single kernel moisture content (MC) is important in the measurement of other quality traits in single kernels because many traits are expressed on a dry weight basis. MC also affects viability, storage quality, and price. Also, if near-infrared (NIR) spectroscopy is used to measure grain traits, the influence of water must be accounted for because water is a strong absorber throughout the NIR region. The feasibility of measurement of MC, fresh weight, dry weight, and water mass of single wheat kernels with or without Fusarium damage was investigated using two wheat cultivars with three visually selected classes of kernels with Fusarium damage and a range of MC. Calibration models were developed either from all kernel classes or from only undamaged kernels of one cultivar that were then validated using all spectra of the other cultivar. A calibration model developed for MC when using all kernels from the wheat cultivar Jagalene had a coefficient of determination (R2) of 0.77 and standard error of ...

Differential accumulation of deoxynivalenol in two winter wheat cultivars varying in FHB phenotype response under field conditions

Abstract Fusarium head blight (FHB) or scab, caused by Fusarium graminearum Schwabe [sexual stage Gibberella zeae (Schwein.) Petch], is a destructive disease of small grain cereals. Fusarium graminearum produces the mycotoxin deoxynivalenol (DON), which accumulates in and lowers the value and quality of grain. Field experiments were conducted from 2007 to 2009 to determine if two winter wheat cultivars varying in FHB phenotype response differentially accumulated DON. Secondary objectives were to model the relationship between FHB severity and DON, determine if environment (= year) influenced DON accumulation in the two cultivars, and measure the percentage of Fusarium-damaged kernels (FDK) in the two cultivars. The cultivar ‘Harry’ with a moderately resistant FHB phenotype consistently accumulated more DON (P ≤ 0.0358) than ‘2137’ with a susceptible phenotype. The relationship between FHB severity and DON was linear and positive for both cultivars in all three years (0.32 ≤ R2 ≤ 0.60; 0.0053 ≤ P ≤ 0.1092). Environment (= year) had a significant effect (P < 0.0001) on DON accumulation in both cultivars, and this effect was attributed to differences in rainfall amount and duration in the months of May and June. DON accumulation was highest in 2008 (average of 33.2 ppm in ‘Harry’ and 21.2 ppm in ‘2137’) when there was steady, above-average rainfall in May and June. FDK was highest in 2008 and was higher in ‘Harry’ (64%) than in ‘2137’ (46%). The results from this study suggest that a winter wheat cultivar with a moderately resistant FHB phenotype can be susceptible to FDK and DON accumulation. Based on these results, there is a need to standardize the criteria (FHB intensity, FDK, DON) for characterizing wheat cultivars as resistant or susceptible to FHB.

Infrared Spectral Properties of Germ, Pericarp, and Endosperm Sections of Sound Wheat Kernels and Those Damaged by Fusarium graminearum

Mid-infrared attenuated total reflection (Mid-IR-ATR) spectra (4000-380 cm−1) of pericarp, germ, and endosperm sections from sound and Fusarium-damaged wheat kernels of cultivars Everest and Tomahawk were collected using a Fourier transform infrared (FT-IR) spectrometer. The differences in infrared absorption bands between sound and Fusarium-damaged kernels were examined. Absorption bands in which differences were identified were compared with the mid-IR-ATR absorption bands of deoxynivalenol (DON) and Fusarium graminearum hyphae. Marked differences in absorption patterns were observed between sound and Fusarium-damaged pericarp and germ spectra, whereas those differences were negligible in the endosperm spectra. Fusarium-damaged pericarp and germ spectra exhibited a shift in the peak position of the band near 1035 cm−1 along with increased absorptions at 1160, 1203, 1313, and 1375 cm−1, likely due to the influence of DON and fungi in the Fusarium-damaged kernel tissue matrix. These results suggest that infrared spectroscopy can detect DON in the surface tissues of Fusarium-damaged wheat kernels.

Near-Infrared Spectroscopic Evaluation of Single-Kernel Deoxynivalenol Accumulation and Fusarium Head Blight Resistance Components in Wheat

Fusarium head blight (FHB) symptoms, single-kernel deoxynivalenol (DON) levels, and distribution of DON levels among kernels in response to artificial FHB inoculation were investigated in three selected wheat cultivars that had different reported levels of FHB resistance. DON levels were estimated with near-infrared spectroscopy. The percentages of DON-containing spikelets per spike of 15.2, 49.7, and 89.1% were significantly different among point-inoculated spikes of Everest, Karl 92, and Overley, respectively. The percentage of visually Fusarium-damaged kernels in point-inoculated Karl 92 and Overley spikes was significantly higher than for Everest. However, the DON-containing spikelets per spike and visually Fusarium-damaged kernels values for spray-inoculated spikes were not significantly different among the three cultivars. In spray-inoculated spikes, DON levels in kernels ranged from 0 to 291.3 ppm, whereas the variation of DON levels in spikelet positions was random. In contrast, DON levels in spik...

Moisture Effects on the Prediction Performance of a Single-Kernel Near-Infrared Deoxynivalenol Calibration

Fusarium head blight (FHB) is a serious disease in wheat that affects grain quality owing to the accumulation of mycotoxins such as deoxynivalenol (DON) in grains. Near-infrared (NIR) spectroscopy has been used to develop techniques to estimate DON levels in single wheat kernels to facilitate rapid, nondestructive screening of FHB resistance in wheat breeding lines. The effect of moisture content (MC) variation on the accuracy of single-kernel DON prediction by NIR spectroscopy was investigated. Sample MC considerably affected accuracy of the current NIR DON calibration by underestimating or overestimating DON at higher or lower moisture levels, respectively. DON in single kernels was most accurately estimated at 13–14% MC. Major NIR absorptions related to Fusarium damage were found around 1,198–1,200, 1,418–1,430, 1,698, and 1,896–1,914 nm. Major moisture related absorptions were observed around 1,162, 1,337, 1,405–1,408, 1,892–1,924, and 2,202 nm. Fusarium damage and moisture related absorptions overlap...