AUDPC Values Research Articles

Response of wheat genotypes against leaf rust (Puccinia triticina) under field conditions

Leaf rust occurs worldwide wherever wheat is grown. The current research was planned to evaluate the response of 37 wheat (Triticum aestivum) genotypes against leaf rust resistance under field conditions during crop season 2017-18.These genotypes were sown in augmented design with two meter long line sowing method with 30 cm row to row distance at research area of Agricultural Biotechnology Research Institute (ABRI), Ayub Agricultural Research Institute (AARI), Faisalabad, Pakistan. After every five genotypes, a line of rust spreader “Morocco” was sown. Moreover, the trial was also surrounded by planting two rows of spreader to increase the inoculum pressure. Data was recorded on the basis of leaf rust severity scale. Leaf rust severity response was variable among tested genotypes. Out of thirty-seven genotypes, five wheat lines were immune (no disease symptoms) i.e. 17BT007, 17BT013, 16BT008, 16BT010 and 16BT011. Seven lines were found to be resistant with AUDPC vales ranged 1-199. Response of ten lines was moderately resistant while five lines were categorized as moderately susceptible. Ten genotypes exhibited susceptible response against leaf rust with more than 600 AUDPC value. High values above 600 of AUDPC showed greater incidence of leaf rust on wheat plants while lower AUDPC values indicated resistance to leaf rust. Present research provided the resistant wheat lines to the breeders to incorporate them in their breeding program against leaf rust.

English

An experiment was conducted at Chefe Donsa naturally infested field with Fusarium oxysporum f. sp. lentis in order to evaluate the effect of lentil genotypes and seedbed types as components of integrated management option. A factorial experiment including lentil variety and seedbed type, each at four levels, was carried out in a split-plot design with three replications. The four lentil genotypes were ILL-590 (susceptible check), Alemaya, Derash and Denbi and four seedbed types were flat bed, open raised bed, tie-raised bed and farmer’s practice. Raised seedbed exhibited relatively lower disease incidence than among the seedbed types. Interaction of the used varieties and seedbed types was significant in wilt reduction. The highest wilt incidence (ca. 67.5%) was recorded on ILL-590, susceptible lentil line, planted on flat bed, whereas, the lowest (ca. 8.8%) Fusarium wilt incidence was noted on cultivar Derash planted in raised bed. A combination of cultivar Derash and raised bed resulted significantly (P<0.05) higher grain yield (3827.0 kg ha-1) than all other treatment combinations. Significantly (P<0.05) lower grain yields (in the order of 68.0 kg ha-1) were obtained from integration of the susceptible genotype (ILL-590) with flatbed than all other treatment integration. The highest (899.4% unit/days) in AUDPC values were observed by flat seedbed type and ILL-590, while the lowest (114.0% unit/days) in AUDPC values were obtained by raised seedbed type and Derash variety. Wilt incidence and AUDPC values were significant and negatively correlated with yield parameters. It was concluded that using moderately resistant variety (Derash) with raised seedbed significantly reduced Fusarium wilt incidence and exhibited reasonably high yields. Keywords: Lentil, management, wilt, F. oxysporum f. sp. lentis. &nbsp

Evaluation of sesame (Sesamum indicum L.) Varieties for Seed Yield and Yield Components under Bacterial Blight (Xanthomonas campestris pv. sesami) Disease Pressure in Western Tigray, Northern Ethiopia

Yield reduction in sesame production in Ethiopia has been attributed to many biotic and abiotic factors. From among the biotic factors, bacterial blight (Xanthomonas campestris pv. sesami) disease is a major constraint across the major sesame growing areas. A study was conducted on farmers’ field at Dansha (northern Ethiopia), “hot spot area” for bacterial blight disease, to identify the level of resistance to bacterial blight disease in some sesame varieties and assess the corresponding productivity of the varieties under natural disease pressure. The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications. Highly significant differences (p<0.01) were observed in days to 50% flowering and maturity, number of branches and capsules per plant, plant height, seeds per capsule, 1000-seed weight, yield (kg/ha), oil content (%) percentage severity index (%) and AUDPC values. The mean maximum yield (651.7 kg/ha) was obtained from variety Gida-Ayana whereas, the lowest mean grain yield (428.3 kg/ha) was obtained from variety Hirhr. Variety Gida-Ayana had the lowest disease development and had the highest seed yield and percent oil content than the rest of the varieties tested. Thus, variety Gida-Ayana is identified as the most promising variety to be produced in the bacterial blight problem areas of northern Ethiopia.

Evaluation of Faba Bean (Vicia faba L.) Varieties against Faba Bean Gall Disease in North Shewa Zone, Ethiopia

Faba bean gall disease is a newly emerging and devastating disease of faba bean that threaten its production and productivity in Ethiopia. Thus, this study was conducted with the objective to evaluate the reactions of faba bean varieties against faba bean gall disease. A field experiment was conducted at Basona Werana and Ankober Districts, in 2014. Sixteen faba bean varieties along with local check were tested in RCBD design with three replications. Faba bean varieties varied significantly (p&lt;0.05) for both disease and yield parameters. The lowest disease severity, AUDPC and infection rates were recorded from variety Gachena (Lay Gorebela) and Gora and Gachena (Mush). Moreover, the highest (2737 and 3374%-days) AUDPC values were recorded from the variety local and Selale at Mush and Lay Gorebela. The highest yield was obtained from varieties Gora, Gebelcho, Degaga, Gachena and Walki (Mush) and from varieties Gora and Gachena (Lay Gorebela). Also, yield of faba bean correlated negatively and significantly with AUDPC and final severity at both locations, whereas, AUDPC and severity associated positively and significantly from each other. From this study it can be concluded that relatively resistant and high yielder varieties can be used in combination with other control measures. Therefore, in the future, researches on integration of resistance and high yielder varieties with other management options should be conducted.

Management of Septoria Tritici Blotch (&amp;lt;i&amp;gt;Septoria tritici&amp;lt;/i&amp;gt;) of Bread Wheat (&amp;lt;i&amp;gt;Triticum aestivum&amp;lt;/i&amp;gt; L.) in the Central Highlands of Ethiopia

Septoria tritici blotch (STB) is an economically important foliar disease in the major wheat-growing areas of Ethiopia. The current research was conducted to determine the impact of wheat varieties and fungicides on disease development and wheat yield. Besides, the effect of bread wheat varieties and fungicides on STB development, wheat yield was evaluated at Holleta and Kulumsa in a factorial field experiment involving three bread wheat varieties and six fungicide spray schedules. At Holetta, variety Kekeba had the highest AUDPC (2548) value followed by Madawalabu and Alidoro; whereas at Kulumsa the highest AUDPC (1509) was recorded on variety Madawalabu followed by Alidoro and Kekeba varieties. STB incidence and severity were significantly reduced by the application of fungicides across varieties but fungicide-variety combinations had differential effects on disease development. Wheat grain yields were the lowest from unsprayed plots regardless of variety and location. Kekeba variety treated with Mancozeb-Tilt-Mancozeb-Tilt (MTMT) fungicide combination produced the highest yield (5.05t/ha). The highest (577.31%) and lowest (-19.95%) marginal rate of return were obtained from Tilt and MTMT sprayed fields at Holetta planted with Kekeba and Madawalabu varieties, respectively. On the other hand, at Kulumsa, the highest marginal rate of return (886.88%) and the lowest marginal rate of return (-63.98%) was obtained from Tilt and Mancozeb sprays on Madawalabu and Alidoro varieties, respectively. The present findings confirmed the importance of STB in Ethiopia and the role fungicides play in managing the disease on partially resistant varieties.

Role of foliage component and host age on severity of Alternaria leaf spot (caused by Alternaria japonica and A. brassicae) in canola (Brassica napus) and mustard (B. juncea) and yield loss in canola

Studies were undertaken under controlled conditions into the effects of different foliage components (cotyledon, first, second and third leaf) at three plant ages (3, 5 and 7 weeks old) on development of Alternaria leaf spot disease, caused by Alternaria japonica or A. brassicae, in canola (Brassica napus cv. Thunder TT) and mustard (B. juncea cv. Dune). Alternaria japonica generally showed percentage disease index (%DI) values similar to A. brassicae across the two Brassica species, different foliage components and plant ages. %DI from either pathogen was greater in older plants than younger plants for the same foliage components in both cultivars. Field studies were then undertaken with canola to compare disease development from A. japonica and A. brassicae across different plant components (leaf, pod and stem) and the consequent adverse impact on seed yield. Alternaria japonica was more severe in terms of leaf area diseased (%LAD 62.6) and stem area diseased (%SAD 69.8) than pod area diseased (%PAD 25.5), whereas A. brassicae was more severe on leaves (%LAD 61.9) than on pods (%PAD 47.4) or stems (%SAD 41.0). Stem disease incidence was greater for A. japonica (%SDI 94.0) than for A. brassicae (%SDI 56.5), but pod disease incidence was greater for A. brassicae (%PDI 93.5) than for A. japonica (%PDI 86.1). For A. japonica, AUDPC values of leaf disease incidence (LDI, 283.5), leaf area diseased (LAD, 253.3) and leaf collapse (LCI, 149.5) resulted in a yield loss of 58.1%, similar to A. brassicae, where AUDPC values of LDI (277.8), LAD (247.2) and LCI (111.0) caused a yield loss of 59.4%. These findings explain observed acceleration of Alternaria leaf spot severity from A. japonica, as from A. brassicae, through the growing season as plants become more susceptible with increasing age, and as more susceptible, later developing leaves become abundant. For the first time, we demonstrate that under conducive field conditions for disease development, A. japonica can cause serious seed-yield losses of a magnitude similar to those occurring with A. brassicae.

EFFECT OF SOIL NUTRIENT AND BIOTA DYNAMICS ON WILT DISEASE SEVERITY IN CHICKPEA

The present study was performed to investigate dynamic and combined effects of soil nutrients (nitrogen and phosphorus) and biotic factors on disease severity of Fusarium wilt in chickpea (AUDPC). Chickpeas were harvested, 180 days after onset of experiment, from eight natural infested soils during two years (2016 and 2017) and assessed for rhizospheric nitrogen (N-TotalR) and phosphorus availability (Olsen-P) in relation to Fusarium oxysporum f.sp ciceris inoculum density (ID-Foc), Trichoderma spp, and Pseudomonas spp as well as nitrogen (N-TotalPL) and phosphorus (P-TotalPL) plants uptake. The results showed that high level of ID-Foc significantly increased AUDPC values. It was found that ID-Foc was negatively correlated with Olsen-P and positively correlated with N-TotalR. Accordingly, AUDPC values were positively correlated with high concentrations of N-TotalR (r=0.77** in 2016, r=0.94*** in 2017) while negatively correlated with high concentrations of Olsen-P (r=-0.73** in 2016, r=-0.79** in 2017). In addition, AUDPC values showed negative interactions with N-TotalPL (r=-0.80** in 2016, r=-0.78** in 2017), whereas positive interactions with P-TotalPL (r=0.80** in 2016, r=0.87** in 2017). Moreover, AUDPC values were negatively associated with Pseudomonas spp and nodosity during the two years of study as with Trichoderma spp in 2017. The results demonstrated that wilt disease severity was strongly associated with nutrients and biological soil properties. It can be assumed that soils with highest Olsen-P levels, Trichoderma spp and Pseudomonas spp can help Fusarium wilt suppression.

Quantification of resistance among basmati rice genotypes to neck blast, Pyricularia oryzae Cavara

Level of resistance to neck blast disease (Pyricularia oryzae) was assessed in 69 rice germplasm lines including susceptible checks (Pusa 1401 and Pusa Basmati 1121) and resistant check (Tetep) under both artificial inoculation and natural epiphytotic conditions. Based on susceptibility index (Sx) value, the level of resistance among the genotypes was classified into moderately resistant (MR), moderately susceptible (MS), susceptible (S) and highly susceptible (HS) categories in comparison with controls. Sx differed significantly among test genotypes ranging from 2.83 to 12.83. Four genotypes viz., Pusa Basmati 1637, INGR 15001, INGR 15002 and Tetep exhibited a moderate level of resistance with Sx value less tahn 3, AUDPC value between 70-140, lesion length between 2-5mm, respectively. Only one entry RYT 3672 showed a moderately susceptible reaction to the disease having Sx value of 5.98, AUDPC value of 169.8 and lesion length of 8.34 mm. AUDPC was positively correlated with lesion length. None of the test entry showed complete resistance to the disease. These entries can be used as donors for strengthening neck blast breeding programme in rice.

Field Evaluation of Trichoderma viride for the Management of Rice Leaf Blast Disease in Pyuthan District, Nepal

A field experiment was conducted at Prime Minister Agriculture Modernization Project (Zone office), Bijuwar, Pyuthan from 18th April, 2017 to 12nd September, 2017 to evaluate the efficacy of Trichoderma viride in the management of leaf blast diseases of rainy season rice under field conditions. The experiment was laid out in two factors factorial Randomized Complete Block Design with five replications. The treatment consisted of two varieties of rice of which one is improved and resistant to blast disease (Sabitri) and another is local (Radha 7) and two rates of Trichoderma viride (5 ml/lit. and 0 ml/lit.). The leaf blast disease was scored three times using the disease rating scale 0-9 given by IRRI, 2002 from 75 DAT to 85 DAT at 5 days interval. The disease incidence, severity and AUDPC value were calculated and analyzed by using RSTAT. The variety factor and Trichoderma viride factor varied significantly for leaf blast incidence, severity and AUDPC, however, the interaction of variety and Trichoderma viride factor varied significantly only in AUDPC value. Disease incidence, severity and AUDPC were found least in Sabitri in comparison to Radha 7. T. viride had significant role in reducing the disease incidence, severity and AUDPC value. The interaction of Sabitri and Trichoderma viride treatment was found best with the mean AUDPC value being the least 3.228. So, the application of Trichoderma viride was found efficient for leaf blast management and it is more effective when applied along with an improved and resistant variety.

Development of a seedling inoculation technique for rapid evaluation of soybean for resistance to Phomopsis longicolla under controlled conditions

BackgroundPhomopsis seed decay (PSD) of soybean (Glycine max L. Merr.) is caused primarily by the seed-borne fungal pathogen Phomopsis longicolla T. W. Hobbs. The PSD disease reduces seed quality and yield worldwide. Development of effective techniques to evaluate soybean for resistance to PSD can facilitate identification of new sources of host resistance to manage the disease. This study was undertaken to develop and utilize a rapid cut-seedling inoculation technique to evaluate soybean genotypes for resistance to P. longicolla under controlled conditions.ResultsThere were no significant differences in stem lesion length determined as the area under disease progress curve at 24 °C and 30 °C. The 21 and 14-day-old seedlings were more susceptible than the older seedlings. Inoculation with 7 or 14-day-old pathogens caused higher values of AUDPC than older pathogen cultures. Isolates MS17-1 was the most aggressive isolate from the test of 25 isolates from seven states in the U.S. Eighteen previously reported field PSD-resistant accessions had significantly lower AUDPC than the susceptible checks and other entries (P ≤ 0.05).ConclusionThis study provided rapid evaluation of soybeans for reaction to P. longicolla and identification of PSD-resistant genotypes. Although PSD is a soybean seed disease, results from the cut-seedling inoculation assays without waiting a whole growing season were comparable to those obtained from field tests. Additionally, concerns about the environmental effects and uneven distribution of the pathogen in the field were ameliorated. The cut-seedling inoculation technique can also be used to speed up evaluation of PSD populations for the discovery of PSD-resistance gene(s), and high throughput phenotyping of seed diseases at seedling stage for genetics and genomic studies.

Chlorophyll content measurement of drought tolerant wheat genotypes sown at normal and late conditions as an indicator of spot blotch resistance

A field experiment was conducted at Agronomy block of the Institute of Agriculture and Animal Science (IAAS), Rampur to evaluate chlorophyll content of 20 drought tolerant wheat genotypes as a parameter of stay green character and spot blotch response. The experiment was laid out in a split plot design with three replications, considering 25 November as normal sowing and 15 December as late sowing dates. Of the tested genotypes, Aditya had highest SPAD value (46.67) with least AUDPC (146) on flag leaf on 25 November sowing and higher SPAD value (43.57) with lower AUDPC (161) on 15 December sowing. Similarly, CSISA DRYT 5204 and CSISA DRYT 5205 had moderate SPAD values with AUDPC value at par with Aditya. Aditya with low AUDPC possessed longer stay green days (118.3) on 25 November sowing and shorter green days (107.5) on 15 December sowing. The susceptible check variety RR-21 possessed shorter stay green days (113.6) with SPAD value (35.7) on 25 November sowing and 100.4 days of stay green with SPAD value (31.23) on 15 December sowing. Aditya also had highest grain yields and thousand kernel weights on both the 25 November and 15 December sowing. The results showed Aditya, CSISA DRYT 5204 and CSISA DYRT 5205 were having longer period of stay green with higher SPAD and low AUDPC values and thus these three genotypes can be recommended for late sown conditions. Journal of the Institute of Agriculture and Animal Science. Vol. 33-34, 2015, Page: 65-72

Screening of maize genotypes against southern leaf blight (Bipolaris maydis) during summer in Rampur, Chitwan, Nepal

A study was conducted during June to September, 2012, in the field at National Maize Research Program, Rampur, Chitwan, Nepal with the objective of screening 20 maize genotypes against southern leaf blight caused by Bipolaris maydis. Experiment was laid out in a randomized complete block design with three replications. Disease scoring was done as percentage of leaf area infected on individual plant at 7 days intervals starting from 50 days after sowing, for 6 times, and disease severity and mean AUDPC were calculated and yield recorded. Among the tested genotypes, there was variation in disease severity and mean AUDPC values. Disease severity was maximum on Yellow Popcorn (51.67%) and least on RML-32/RML-17 (7.27%). Based on mean AUDPC values, RML-32/RML-17 (20.53) appeared most resistant, followed by RML-4/NML-2 (23.66) and RML-4/RML-17 (25.90), while Yellow Popcorn (136.9) was found the most susceptible. Highest grain yield (4.90 t/ha) was also recorded on RML-32/RML-17 and least (2.49 t/ha) on Yellow Popcorn. Therefore the genotypes RML-32/RML-17, RML-4/NML-2 and RML-4/RML-17 could be used as the resistant varieties and source of resistance to southern leaf blight for varietal development of maize.Journal of the Institute of Agriculture and Animal Science.Vol. 33-34, 2015, Page: 115-122

Potensi Cendawan Endofit sebagai Pengendali Hayati Penyakit Busuk Pangkal Batang (Phytophthora capsici) pada Bibit Cabai

Stem rot disease caused by Phytophthora capsici is an important disease on chilli. Eight endophytic fungi that had been isolated and screened based on pathogenecity test were further tested for their potential as the biological control agent of the stem rot disease of chilli. The endophytic fungi suspension was applied twice during the trial. The first application was on 100 seed lot, by soaking them in 100 mL of suspension. The second application was on the 3 weeks-old chili seedlings by drenching them with 10 mL suspension per plant. The concentration of endophytic fungi in the suspension was 2.8 × 106 cfu mL-1. The disease intensity and AUDPC value were measured for 4 weeks after the pathogen inoculation. The growth inhibition test of P. capsici was performed in vitro and the colonization abilities of endophytic fungi were observed at 4 weeks-old chilli seedlings. Eight endophytic fungi inhibited the growth of the P. capsici, and two of those isolates namely Penicillium strain MAG1 and Penicillium strain PAB2 showed antibiosis mechanism. Endophytic fungi has the ability more to colonize at the root (26–60%) than in the stem (20–40%). Fusarium strain MAGR1 has the highest level of endophytic colonization i.e. 60% compared to others. Based on in vivo assay, six endophytic fungi isolates, i.e. Fusarium strain MAGR1, Penicillium strain MAG1, Penicillium strain PAB2, sterile hyphae HAJ1, sterile hyphae HAJ2, and sterile hyphae PBG7, showed the potency to control stem rot disease with inhibition level of 25.5–35.5%

Combining ability and nature of gene action in maize (Zea mays L) inbred lines for resistance to gray leaf spot disease (Cercospora zeae maydis) in Ethiopia

Ten elite maize inbred lines were selected based on all over per se performance and gray leaf spot disease reaction. Crosses were made in a 10 × 10 half-diallel mating design to produce 45 F1 single cross hybrids. The experiment was conducted at Bako national maize research center in 2015 and evaluation of the crosses were made at Bako and Jimma research centers in 2016 by using alpha lattice design with three replications including three commercial checks. All the necessary yield, agronomic and GLS disease data were recorded. In all the studied traits highly significant genotypic differences were observed indicating the existence of genetic variability among the crosses. Analysis of variance for the combining ability indicated GCA and SCA mean squares were significant at (P < 0.001) for all traits except for anthesis-silking interval, ear per plant, ear diameter, lesion length and width. The ratios of GCA/SCA variances for agronomic parameters and all disease parameters were greater than unity except for that of first disease appearance implying the predominance of additive gene actions. Among all inbred lines, P1, P4, P7, P8 and P9 were identified as desirable sources of resistant genes for GLS disease resistance with positive days of first disease appearance and negative disease incidence, severity and AUDPC values for GCA effects. From the analysis of epidemiological data and disease progress curves the Logistic model (R2 = 96.5) better described the disease progress curves than the Gompertz model (R2 = 92.5) indicating the presence of delayance in epidemics and the inflection point of the GLS. P1, P7 and P8 were identified as a good general combiners for yield, yield related traits and GLS disease parameters. Thus, these parents were recommended to be used in breeding programs with a purpose of developing high yielder and GLS resistant single cross hybrids. In conclusion this study identified potential high yielding and GLS resistant single cross hybrids (CML-395/CML-383, CML-395/Sc-22, CML-395/CML-197 and CML-383/CML-197). Therefore, it is recommended that these hybrids can be used for direct production where this disease is the most prevalent and/or for further breeding programs in generating novel hybrids for future use.

Implication of Fungicide Application Regimes and Post Spray Irrigation on Late Leaf Spot and its Residual Impact on Stem Rot of Groundnut

A field experiment was conducted during rabi season of 2015-16 and 2016-17 to study the efficacy of different protectant and systemic fungicides in different application regimes on late leaf spot disease of groundnut and to assess the impact of post spray irrigation timing on the severity of late leaf spot and as well as management of stem rot disease through deposition of foliar applied fungicides. Three sprays of chlorothalonil @ 2g/l (1th, 3rd, 5th) alternated with three sprays of pyraclostrobin @ 1g/l at 2nd, 4th and 6th spray (T8) reduced the highest disease severity (40.74%) as compared to seven spraying of chlorothalonil (T2) at 10 days interval (60.00%). The AUDPC values were significantly different among various treatments. Highest yield (28.89 q/ha) was also recorded in T8. The number of late leaf spot lesion decreased with the increase in gap between spraying and irrigation time. Irrigation after 96 h of fungicide spray caused only 2.02 leaf spot lesion per leaflet and highest pod colonization of 43.63% due to stem rot. Negative correlation was found between pod colonization and number of leaf spot lesion.

Field Experiment to Evaluate the Efficacy of Different Doses of Chemical Fungicides against Rice Brown Leaf Spot Disease Caused by &lt;i&gt;Bipolaris&lt;/i&gt;&lt;i&gt; &lt;/i&gt;&lt;i&gt;O&lt;/i&gt;&lt;i&gt;ryzae L&lt;/i&gt;. at Paklihawa, Rupandehi, Nepal

Brown Leaf Spot of Rice, caused by the Pathogen Bipolaris oryzae, is one of the important rice diseases resulting in high yield reduction and poor grain quality. A field experiment was conducted to evaluate the efficacy of different doses of chemical fungicides against brown leaf spot in ‘SabhaMansuli’ variety of rice in the research field of Institute of Agriculture and Animal Sciences, Paklihawa Campus from July 15, 2015 to December 1, 2015. The experimental design was RCBD with three replications and ten treatments. Treatments comprised of three different chemical fungicides; SAAF® (Carbendazim 12% + Mancozeb 63%), Tilt® (Propiconazole 25 EC) & Bavistin® (Carbendazim 50% W.P.) at three different doses of 1.5, 2 & 2.5 g (or ml) and a control plot. Among the different fungicides, Tilt® at the rate of 2 ml/lit water showed significantly lowest AUDPC value (373.7) followed by SAAF® at 2 gm/lit (374.9) while the highest value was shown by Bavistin® at 2gm/lit (590.1).Similarly, highest economic yield was obtained in SAAF® at 2gm/lit (5.220 t/h) followed by Tilt® at 2ml/lit water (5.210t/ha) and the lowest in Bavistin® at 1.5gm/lit (3.320t/ha). So, among different chemical fungicides, SAAF® at 2gm/lit being efficient, economical and easily accessible, farmers could be suggested for reducing the disease severity and subsequent increase in the yield of rice.

Yield and resistance of potato cultivars with colour flesh to potato late blight

The resistance to potato late blight (as AUDPC – the area under the disease progress curve) and yield were evaluated in precise field experiments with 13 colour-fleshed potato cultivars. Red Emmalie and Blaue Anneliese were the most profitable cultivars of potatoes with coloured flesh, the overall yield did not differ statistically from the control cv. Agria. Cv. Blaue Anneliese resistance to potato late blight was considerably better than both control cultivars, other 2 cultivars HB Red and Red Emmalie were similar to cv. Agria. Surprisingly, cv. Russet Burbank was found to be more resistant than most cultivars tested. A statistically significant weak dependence (r = 0.36) between the percentage of infestation of plants in the T6 evaluation date (6–8 August in individual years) and the yield was detected, the slightly stronger (r = 0.40) was the correlation between AUDPC values and total yields.

Effect of mineral nutrients, seed treatment and foliar fungicides on spot blotch (Bipolaris sorokiniana) severity and agronomic performance of wheat (Triticum aestivum) in hot-humid environment of eastern Gangetic plain in India

Spot blotch disease [Bipolaris sorokiniana (Sacc.)] is one of the most serious biotic constraint affecting wheat production in India. The effect of balanced macro- and micro-fertilization, fungicidal seed treatment and foliar fungicides either individually or in combination were assessed for their impact on spot blotch severity, grain yield, and other yield attributing characters during 2012-13 and 2013-14. Average maximum temperature (27.0°C) and high relative humidity (&gt;90%) in February and March during both the years favoured disease development and spread. In vitro analysis of untreated pre-sown seeds using a blotter paper test revealed 19.2% and 32.5% seed infection with B. sorokiniana during 2012-13 and 2013-14, respectively. At the end of each cropping season, seed infection in harvested seed lots ranged from 5-6% in treatments with a combination of balanced fertility, seed treatment and foliar fungicide, 13% following two sprays of propiconazole, and 71% in control treatment. Application of balanced nutrition alone reduced AUDPC by 37% and increased grain yield up to 26%. However, the combined influence of balanced nutrition, carboxin + thiram seed treatment and two foliar sprays of propiconazole resulted in a 99% reduction in AUDPC values with 60% higher grain yield (6.30 t/ha), 45% higher TKW (41.33 g) and significant increase in other yield attributes. The current study illustrates the role of a combination of crop and disease management practices in the control of spot blotch and improving the agronomic performance of wheat in eastern plains of India.

Screening of Maize Genotypes against Southern Leaf Blight ( Bipolaris m aydis ) during Summer Season in Nepal

A study was conducted from 29 March 2014 to 27 July 2014 at the Institute of Agriculture and Animal Science, Paklihawa, Rupandehi with the objective of screening 13 maize genotypes against southern leaf blight caused by Bipolaris maydis. Field experiment was laid out in a randomized complete block design with three replications. Disease scoring was done as percentage of leaf area infected on individual plant at 5 days intervals starting from 63 days after sowing, for 3 times, and disease severity and mean AUDPC were calculated and yield was recorded. Among the tested genotypes, disease severity varies significantly. Disease symptoms appeared first in Yellow Popcorn, 64.00 days after sowing (DAS) with the highest severity and at last in RML-32/RML-17 (79.00 DAS) with the least score in field. The 13 genotypes differed significantly in mean AUDPC values. RML-32/RML-17 (AUDPC value 5.90) appeared most resistant, followed by RML-4/RML-17 (AUDPC value 11.50), while Yellow Popcorn (AUDPC value 71.99) was most susceptible among the tested genotypes. Highest maize yield (3.43 metric ton ha-1) was also recorded on RML-32/RML-17 and least (0.75 metric ton ha-1) on Yellow Popcorn. Maximum SPAD value above cob was recorded in RML-4/RML-17 (45.62) followed by S03TLYQ-AB-01 (44.88) while minimum in Yellow popcorn (30.60). So, Yellow popcorn has the highest (3.16) and RML-32/RML-17 (0.08) lowest total AUDPC above cob. Similarly maximum SPAD value below cob was recorded in RML-4/RML-17 (44.37), while minimum in Yellow popcorn (28.82). So, Yellow popcorn has the highest (8.75) and RML-32/RML-17 (0.41) has lowest total AUDPC below cob. The genotypes RML-4/RML-17 and RML-32/RML-17 appeared resistant to SLB with maximum yield. These genotypes could be used as the sources of resistance in breeding program and could be developed to resistant varieties grown under tropical and subtropical climatic conditions during summer season. The genotype Yellow popcorn being highly susceptible to SLB with a maximum mean AUDPC and minimum yield, can be used as susceptible check for breeding purpose and different varietal screening.

Evaluation of Fungicides and Fungicidal Spray Schedule for the Management of Angular Leaf Spot of Common Bean

Angular Leaf Spot (ALS), caused by Phaeoisariopsisgriseola (Sacc.), is one of the major diseases of common bean in the Southern Ethiopia.The objective of the experiment was to select fungicides and spray intervals to recommend low cost management options for the control of ALS disease. The experiment was carried out under natural epidemic at Awassa Agricultural Research Center in Southern Ethiopia during 2013 -2014. The study consisted of five different fungicides (Ridomil Gold, Penncozeb, Curzate, Tilt 250 EC and Bumper 25 EC) in combination with two spray intervals ( 7 and 14 days) using two common bean varieties (HawassaDume and Red Wolaita) having dissimilar levels of reaction to ALS. The treatments were laid using Randomized Complete Block Design (RCBD) in factorial arrangement. All fungicides tested were found to be effective in controlling the ALS disease as compared to unsprayed treatment. Ridomil Gold was the most effective fungicide in reducing the disease severity and yield loss,followed by Curzate and Penncozeb, where asPropiconazole fungicides (Tilt 250 and Bumper) showed high AUDPC value as compared to the other fungicides. Ridomil Gold reduced the AUDPC value by 75% and 40% on susceptible and moderately resistant varieties, respectively. Grain yield loss was estimated to be 35 to 40 % and 74 to 85 % in moderately resistant and susceptible variety, respectively. There was not significance difference (p