Highest Area Under The Disease Progress Curve Research Articles

Pathogenic variation of Olpidium viciae isolates on faba bean varieties and other legumes

Faba bean is an important cool-season food legume currently constrained by an emerging gall disease (Olpidium viciae) in Ethiopia’s highlands. Variability tests of O. viciae isolates were conducted to determine its pathogenic variation on six faba bean varieties in the growth chamber and eight other legumes in the screen house. Each faba bean variety and legume was inoculated with zoospores suspension (106 spores mL−1) of each isolate. The variability tests were conducted twice on six faba bean varieties to identify the pathogenic level of 30 O. viciae isolates and the experiments were factorially arranged in a completely randomized design with three replications. There was significant variation (P < 0.01) among faba bean varieties, other legumes, and isolates in the components of disease development in both experiments. Isolates ST8 and SL4 caused the highest disease severity (34.23%) and area under the disease progress curve (AUDPC) (180.56%-days) on faba bean variety Bulga 70. Seven pathogenic isolates were identified as causing more disease on faba bean varieties than the remaining 23 isolates and then inoculated on other legumes. Isolate SEL caused the highest disease severity on grass pea (Lathyrus sativus) (20.99%). Next to faba bean, higher AUDPC (156.64%-days) was calculated from inoculated grass pea with WQZ isolate. Thus, the isolates varied in their infection ability in the tested legumes and faba bean varieties, and the pathogen had a wide range of hosts.

Phenylalanine ammonia lyase (PAL) contributes to the resistance of black rice against Xanthomonas oryzae pv. oryzae

In this study, we focus on the phenylalanine ammonia lyase (PAL) as one of the possible defense factors of black rice (a black colour mutation of Oryza sativa, containing a high amount of anthocyanin and other antioxidants) against Xanthomonas oryzae pv. oryzae (Xoo), causing bacterial leaf blight of rice. Two black rice varieties namely Pari Ireng and Melik, and three white rice varieties (IRBB21, Java14, and IR64) as control were used in this study. The analysis of the resistance trait was performed by determining disease intensity (DI) and area under the disease progress curve (AUDPC). The determination of PAL activity was performed using HPLC by analyzing trans-cinnamic acid as a product of PAL enzyme by in vitro bioassay. Protein profile analysis using SDS-PAGE was also performed to compare the profile of the infected and non-infected plants. The results showed that Java 14 (positive control) has the highest AUDPC (107.59) followed by Pari Ireng (128.33), Melik (199.63), and IRBB21 (250.19). Meanwhile, IR64 has the lowest AUDPC (304.63) which was consistent as a negative control. There was a significant increase in PAL enzyme activity in Pari Ireng, Melik and Java 14 but not in IR64 and IRBB21 following Xoo infection. Those results indicated that PAL contributes to the resistance mechanism against Xoo. The distinctive protein profile (ranged from 48 to 75 kDa) was also observed between the infected and non-infected cultivar. Based on our results, Pari Ireng was classified as a resistant cultivar against Xoo.

SEVERITY OF RAMULARIA LEAF SPOT AND SEED COTTON YIELD IN DIFFERENT SOWING TIMES

ABSTRACT The ramularia leaf spot (RLS) disease causes cotton yield losses. Choosing a less susceptible cultivar and a sowing time that are less favorable to the pathogen contribute to the management of this disease. The objective of this work was to evaluate the severity of ramularia leaf spot on cotton cultivars sowed in two different times. The experiment was conducted in a triple factorial design (4x3x2), consisted of four cultivars, the three thirds of the plant and two sowing times, with four replications. Each plot was divided in two twin plots, one with fungicide application (with disease control) and the other without fungicide application (without disease control). The severity assessments were performed every seven days, considering each third of the plant with a diagrammatic scale. Yield was evaluated in each plot. There was a significant interaction between sowing times and the thirds of the plant in the plots without disease control for RLS severity, with the highest values of area under the disease progress curve (AUDPC) in the first sowing time (ST1) and in the lower third of the plant. The FMT705 cultivar had the highest and FM951LL the lowest value of AUDPC. The AUDPC of these cultivars were no statistically different in the second sowing time (ST2), but they had higher AUDPC values in the lower third. Highest yields were found with ST1 in plots with disease control, with no differences between the cultivars, however, lower yields were found in plots without disease control.

Integrated management of Ascochyta blight (Didymella fabae) on faba bean under Mediterranean conditions

Integrated disease management options (two sowing dates, three fungicides and 3–6 faba bean genotypes) in managing Ascochyta blight affecting faba bean were evaluated for three cropping seasons (2006/07–2008/09) in northern Syria for their effects on disease parameters, seed infection and dry seed yield. The combined results of the three seasons on disease parameters showed that sowing dates significantly affected final disease severity and area under the disease progress curve (AUDPC); faba bean genotypes significantly affected final disease severity, rate of disease development and AUDPC. The highest AUDPC (255% days) was observed in early than late planted (168% days) faba bean genotypes. The mean AUDPC of faba bean genotypes ranged from 189% days on genotype 1053–1325 to 234% days on ILB-1814. Only faba bean genotypes and fungicides showed significant interactions in affecting final disease severity and AUDPC. Fungicide sprays significantly affected mean percent pod infection and rate of disease development but not mean percent seed infection. Faba bean genotypes showed significant differences in dry seed yield and the yield ranged from 1.7 t ha−1 in cv. Ascot to 2.4 t ha−1 in faba bean genotype 945-105. Improved varieties with Ascochyta blight resistance are not currently released and available for farmers in northern Syria and the integration of early planting (November–December) with one foliar fungicide spray at vegetative stage can help to reduce Ascochyta blight severity, pod and seed infections. Chlorothalonil and azoxystrobin are widely used fungicides to manage Ascochyta blights on food legumes in many countries and one of them could be used depending on their availability and costs to managing faba bean Ascochyta blight in Syria and other Mediterranean type environments.

A comparison of web blight epidemics on common bean cultivars with different growth habits

The progress of web blight caused by Thanatephorus cucumeris on common bean (Phaseolus vulgaris) “Carioca” cultivars with different growth habits was compared in a three-season study. Field trials were conducted in 2004/2005, 2005/2006 and 2006/2007 in a naturally infested area, with 10 susceptible cultivars from group I (determinate bush, upright plants: cvs. Iapar 81, BRS Horizonte and FT Magnífico); group II (indeterminate bush plants: cvs. BRS Pontal, and Pérola) and group III (plants of indeterminate prostrate growth: cvs. BRSMG Talismã, Aporé, BRS Requinte, Carioca, Carioca Precoce). Severity of web blight was assessed weekly and the resulting progress curves were fit to the monomolecular model. Overall disease impacts were estimated by the area under the disease progress curve (AUDPC), disease progress rate and disease onset. No significant interaction between AUDPC and planting season was detected. Cultivars BRS Horizonte, FT Magnífico and Iapar 81, with upright architecture, short guides, high pods and closer branches presented the lowest AUDPCs. The highest AUDPCs were found among indeterminate lodged plants with long guides and low pods (cvs Aporé and Carioca Precoce), while indeterminate bush cultivars were fitted in an intermediate rank. Differences in disease epidemics among the three groups were confirmed by intercept and disease progress rates of linearized models. Such parameters were significantly lower for upright genotypes, probably because they result in late contact between neighbor plants and consequently delay the establishment of conducive microclimate and mycelial bridges for web blight development. Yields were strongly reduced due to the extremely high disease levels that prevailed at all three seasons. Nevertheless, a negative correlation between grain yield and web blight severity was significant in 2006/2007. Despite the fact that the number of cultivars is too small to generalize responses on escape to web blight, results evidenced that choice of plant architecture is a useful strategy for web blight management.

Advancement toward New Spot Blotch Resistant Wheats in South Asia

Spot blotch, caused by Cochliobolus sativus, is a constraint to wheat (Triticum aestivum L.) production in South Asia. A set of genotypes was grown in Bangladesh, India, and Nepal to assess the current status of genetic resistance across locations. This study examined spot blotch resistance and agronomic performance of 24 wheat genotypes through regional trials in 2003, 2004, and 2005 and the estimated reduction in yield caused by spot blotch. We analyzed the area under the disease progress curve (AUDPC) and AUDPC d−1 to assess spot blotch severity, and recorded grain yield, 1000-kernel weight (TKW), days to heading, and plant height. Disease severity differed in the 3 yr. The highest AUDPC d−1 in 2005 was associated with the lowest grain yield, with an average 14.8% disease-induced yield reduction. Several genotypes showed low disease severity. A few genotypes had high grain yield. A few resistant genotypes such as Milan/Shanghai #7, Chirya.1, and Chirya.7 had grain yield reductions of about 5%. The genotype BL1473 showed high disease severity but low (∼5%) disease-induced reduction in grain yield. The genotype Milan/Shanghai #7, with the lowest disease severity and highest grain yield, was also the most stable for spot blotch resistance and grain yield. The results indicated that wheat genotypes with improved spot blotch resistance, high grain yield, acceptable TKW, and plant height are available as a result of the international collaboration in South Asia.

Components of partial resistance to Stagonospora blotch among Brazilian spring wheats

Thirty-two Brazilian spring wheats (Triticum aestivum L. em. Thell.) were evaluated for partial resistance to Stagonospora blotch under greenhouse conditions to an isolate of Stagonospora nodorum from the southeastern U.S. Incubation period was shortest (5.6 days) in the susceptible cultivar BR 4 and longest (12.7 days) in the resistant cultivar CEP 14. Latent period was significantly longer for CEP 14 than on any other cultivar except BR 38. Resistant wheats had latent periods that were 3–5 days longer than susceptible lines. Disease severity was negatively correlated (P < 0.01) with incubation period and latent period. Cultivars with long incubation period and long latent period also had a slow rate of disease progress. The widest range of response to S. nodorum infection was for area under the disease progress curve (AUDPC). CEP 14 and BR32 had AUDPC values that were less than 25% of the values of seven cultivars with the highest AUDPC. CEP14 had the longest IP and LP and the lowest AUDPC, exceeding the next closest entry by almost 5% for each parameter. Ratings for components of partial resistance closely paralleled field ratings for resistance in southern Brazil. Because genotypes are generally well-adapted agronomically and responded similarly to an isolate representative of S. nodorum in the southeastern U.S., resistant lines from southern Brazil may be useful in breeding programs in the southern U.S.