Lower Area Under Disease Progress Curve Research Articles

Screening of onion (Allium cepa) genotypes to find out novel resistant source against purple blotch (Alternaria porri)

Purple blotch caused by Alternaria porri (Ellis) Cif., 1930 causes huge losses to bulb crop and seed crop of onion (Allium cepa L.). This is a major disease affecting successful onion production in majority of the onion growing areas. To identify resistant source against purple blotch, 34 onion genotypes with good marketable yield based on field evaluation trial in 2017 and allied species Pusa Soumya were screened under protected conditions during kharif, 2018 at insect proof net house facility of ICAR-Indian Agricultural Research Institute, New Delhi. The pure culture of Alternaria porri, isolated from infected leaf samples of onion crop raised under natural epiphytotic conditions during kharif, 2017. Highest change of disease severity index was observed between 1–2 weeks post inoculation (WPI) while highest disease severity index was recorded at 5 WPI suggesting that preventive measures must be employed as soon as disease symptoms appear in the field. The disease severity index ranged from 0.10–33.33 at 1 WPI, which increased to 9.33–89.33 at 5 WPI. The cultivated allied species Pusa Soumya was identified as novel resistance source with DSI value less than 10.0% at 5 WPI. Four genotypes exhibited moderately susceptible reaction, while 20 genotypes were susceptible and 10 genotypes were highly susceptible. The area under disease progress curve (AUDPC) value ranged from 22.33–240.17. Pusa Soumya had the lowest value and among onion lines Arka Kirtiman was found promising. Three onion genotypes had low relative AUDPC value and can effectively be utilized in resistance breeding programme. The average daily temperature between 20–25°C and relative humidity above 75% was found ideal for disease development.

Partial Resistance Components and Morphological Traits Aid Selection of Resistant Wheat Genotypes against Spot Blotch

Spot blotch caused by Bipolaris sorokiniana results substantial yield losses (15-80%) in an Indian subcontinent. Wheat varietal improvement through breeding followed by evaluation of elite germplasms against a particular disease is crucial method to manage diseases. Fifty diverse wheat genotypes and two susceptible checks viz., Sonalika and Nepal 297 were evaluated under artificial epiphytotic condition against spot blotch at NWRP, Bhairahawa, Nepal in 2017-18 and 2018-19. Evaluation was based on partial resistance components viz., lesion sizes, lesion types (chlorotic/ necrotic), lesion characteristics (sporulating/ non-sporulating) and area under disease progress curve (AUDPC) and morphological traits viz. lesion mimic, leaf angle, leaf tip necrosis and plant height. Statistical analysis revealed that genotypes with smaller lesion size (<1 cm), small dark brown to black lesions with or without chlorosis/ necrosis and non sporulating lesions had lower AUDPC (<225). Similarly genotypes with erect to semi erect leaf (leaf angle 1-2), medium to high leaf tip necrosis (2-4), low percentage of lesion mimic (0-22.5%) were found resistant (AUDPC<225) to moderately resistant (AUDPC value 226-315). Moreover AUDPC showed strong and positive correlation with lesion sizes (0.76), lesion types (0.84) and lesion characteristics (0.54). Twenty genotypes were found resistant (AUDPC<225), could be used as new resistance sources in breeding program. However genotypes viz., KACHU/BECARD//WBLL1*2/BRAMBLING/3/ATTILA*2/PBW65//MURGA, FRET2*2/SHAMA//TNMU/3/FRET2*2/SHAMA/4/UP2338*2/KKTS*2//YANAC/5/FRET2*2/SHAMA//PARUS/3/FRET2*2/KUKUNA, KACHU#1//PI610750/SASIA/3/KACHU/4/MUU#1//PBW343*2/KUKUNA/3/MUU/5/KACHU#1//PI610750/SASIA/3/KACHU, BORL14//KFA/2*KACHU and KFA/2*KACHU//QUELEA were found excellent based on partial resistance components and morphological traits. These genotypes could be further evaluated for yield potential in multi environment and better performing genotypes could be released as resistant varieties for spot blotch.

Host resistance by sowing date interaction reduced Fusarium wilt pressure and improved grain yield of chickpea (Cicer arietinum L.) in North Shoa, Ethiopia

AbstractChickpea Fusarium wilt is seriously damaging chickpea productivity. To determine the integrated effects of three sowing dates and four chickpea varieties on epidemics of Chickpea Fusarium wilt and grain yield, field experiments were conducted in naturally infested soils at Alem Ketema and Enewari, Ethiopia, during 2018. Treatments were factorial arranged in a randomized complete block design with three replications. Results showed that variety Mastewal recorded relatively low mean Fusarium wilt incidence at Alem Ketema (15.344%) and Enewari (38.19%) compared with the other test varieties. Variety Mastewal also produced high grain yield over others at Alem Ketema (1155.14 kg ha−1) and Enewari (1120.91 kg ha−1). Related trends were observed for infection rate, area under disease progress curve (AUDPC), and yield components at both locations. Late August sowing resulted in higher stand count at harvest (132.08 and 102.08), number of pods (50.28 and 40.62), grain yield (1030.86 and 1122.08 kg ha−1), and lower AUDPC value (321.30%‐days and 540.34%‐days) than early August sowing in that order at Alem Ketema and Enewari. Interaction of variety Mastewal by late August sowing gave relatively high grain yield (1341.36 and 1331.85 kg ha−1), and it had low AUDPC (196.58%‐days and 483.36%‐days) at Alem Ketema and Enewari, respectively. Conversely, early planting caused up to 25.32% (Alem Ketema) and 193.67% (Enewari) yield reductions in chickpea varieties over late planting. Therefore, delaying sowing date and growing variety Mastewal found to maximize chickpea yield and minimize effect and progression of Fusarium wilt, and hence, recommended for the study areas.

Evaluation of Improved Cowpea Genotypes for Yield and Resistance to Scab Disease in Uganda

Cowpea is one of the most important legume food crops in Uganda. However, grain yields as low as 400 kg ha−1 have been recorded in farmers’ fields despite a grain yield potential of 3,000 kg ha−1. Cowpea scab is a major production constraint, causing yield losses of up to 100%. Three hundred ninety (390) improved cowpea genotypes were evaluated for yield and scab resistance for one (1) year at NaSARRI, Serere, Uganda using an alpha lattice design with two replications. The analysis of variance showed significant differences (p < 0.05) for grain yield, scab severity, incidence, and area under disease progress curve (AUDPC) among genotypes, seasons, and for genotypes by seasons interactions. The mean grain yield of 981.6 kg ha−1 was recorded across the cowpea genotypes with genotype, TVU-1280 having the highest grain yield of 1790.8 Kg ha−1. The cowpea genotypes; 1195K-1093-5-A, TVU-2968, SanZi, Taef-14-inhaca.E, TVU-205-8 and TVU-13485 had low scab severity(range:8.0 - 9.0).Cowpea genotypes; Taef-14-inhaca.E(33.7%), TVU-14633(26.7%), TVU-151144(30.6%), and Cosiriele (31.4%), had low scab incidence. Low AUDPC (range: 788.8-883.5) was observed in cowpea genotypes; 1195K-1093-5-A (775.0), TVU2968(788.8), TVU-14633-A (883.8), and TVU-13388 (857.5). Grain yield had a significant negative correlation with AUDPC (r = −0.2279, p < 0.001) and scab severity (−0.600, p < 0.001). Scab severity showed a strong significant and positive correlation with AUDPC (r = 0.6873, p < 0.001). The cowpea genotypes; 1195K−1093−5−A, TVU−2968, TVU−15114, SanZi, and Taef−14− inhaca.E could be used as breeding lines for introgressing scab resistance into cultivars with farmer preferred traits.

Identification of Source of Resistance to Horse Gram Yellow Mosaic Disease (HgYMD) in French Bean (Phaseolus vulgaris L.)

Background: Horse gram yellow mosaic disease (HgYMD) is one of the major limiting factor for legumes production in India as it can cause economic loss up to 100%. Till date, horse gram yellow mosaic virus was rare to infect french bean, but now-a-days, it has become the major causal agent for yellow mosaic epidemics in the southern part of India. Few bush type varieties, resistant to yellow mosaic disease are released but not specifically resistant to HgYMD. So, systemic breeding work has been initiated to identify the resistant source for HgYMD in french bean. Methods: Seventyone genotypes of french bean were screened in a randomized complete block design (RCBD) with three replications under natural epiphytotic as well as artificial condition during Summer, 2018 at ICAR-IIHR, Bengaluru, India. Result: The genotypes varied for percent disease index (PDI), area under disease progress curve (AUDPC) and the apparent rate of infection per unit time period (r). Two varieties i.e., Jade-5058 and Arka Arjun were showing less PDI of 13.33 and 14.44, least average rate of infection of 0.64 and 0.65 and lowest AUDPC value of 350.54 and 359.16 respectively, compared to other genotypes. Average PDI of Arka Arjun and Jade-5058 were 13.33 and 12.22 under artificial screening, which were much lesser than susceptible check Arka Komal (PDI 92.22) and Arka Anoop (PDI 90.00). Resistant genotypes identified from this experiment can be used for breeding HgYMD resistant french bean lines.

Cultivar, planting date and weather linked to wheat leaf rust development

During four growing seasons (2013–2017), 282 leaf rust progress curves were characterized across experimental plots according to a number of climate-crop-disease variables in Kermanshah province, Iran. Leaf rust severity differed significantly between levels of cultivar, planting date, sampling time and year factors. Area under disease progress curve (AUDPC) based on disease severity was ranked using Kruskal–Wallis one-way ANOVA. H-test comparison between two disease-onset levels indicated lower mean AUDPC value for late disease onset than that for early disease onset. Highest and lowest AUDPC values were obtained in spring 2016 and 2015, respectively. According to principal component analysis, three principal components accounting for 73% of data variance verified dependence of leaf rust intensity on air temperature and wetness, cultivar resistance, date of disease onset, wheat maturity, and planting date. Based on principal component regression model, disease-onset and maturity date, mean 6-monthly temperature, number of days with minimum temperatures within the range of 5–25 °C and maximum RH > 60%, resistance index, and planting date justified 74% of variability in AUDPC dataset. These findings recommend involvement of cultivar resistance, dates of wheat maturity and planting along with weather predictors in wheat-leaf-rust studies to increase prediction value of future models, durability of host resistance to disease, and sustainability of disease control methods.

Relative susceptibility of commercial watermelon varieties to powdery mildew

Powdery mildew (PM) of watermelon caused by Podosphaera xanthii has been occurring more frequently in recent years than in the past and now growers routinely apply fungicides to manage PM. Powdery mildew is known to be able to cause a significant yield reduction in watermelon. The current study was conducted in 2014, 2015 and 2016 to determine the relative susceptibility of twenty six watermelon varieties (seeded and seedless) and three pollenizers to P. xanthii populations prevailing in Charleston, South Carolina. USVL677-PMS, which is highly susceptible to PM and USVL531-MDR, which is resistant to PM were included as controls. A randomized complete block design with three replications was used each year and plants were rated on a 0–10 scale of increasing disease severity. During all three years, USVL677-PMS was the most susceptible line with the highest values for area under disease progress curve (AUDPC). Disease severity at the last ratings for USVL677-PMS ranged from 61 to 82%. In comparison USVL531-MDR was very resistant to PM based on disease severity (1–3%) and AUDPC. The commercial pollenizers, SP5, SP6 and Lion were all resistant to PM (1–5% disease severity) and had significantly lower AUDPC compared to USVL677-PMS and most other varieties evaluated. Among the red fleshed varieties, Suprema (seedless variety), was relatively resistant compared to other seeded and seedless varieties. Most of the seeded varieties evaluated (e.g. Malali, Black Mama, Mickey Lee) were highly susceptible to PM, however, some were relatively less susceptible (e.g. Declaration) under field conditions. Currently very few to no varieties with high levels of resistance to PM are available and there is a need to develop newer resistant varieties as PM is occurring more frequently during the growing season.

Evaluation of Ethiopian Durum Wheat Varieties and Landrace Cultivars for the Adult Plant Resistance of Wheat Leaf Rust (Puccinia triticina)

Wheat Leaf rust caused by the pathogen Puccinia triticina is a serious threat of wheat production in Ethiopia, yield loss due tothis disease reached up to 70%. A study was carried out to identify leaf rust adult plant resistance in commercial durum wheatcultivars and landraces. 35 durum wheat Varieties and 200 durum wheat landraces with three susceptible checks arranged inAugment design and evaluated against leaf rust at Debere Zeit Agricultural Research Center, Ethiopia during the 2017/18 mainseason. Terminal Rust Severity (TRS), Coefficient of Infection (CI), Area under Disease Progress Curve (AUDPC) and Disease Progress Rate (DPR) were used to measure leaf rust adult plant resistance in the test materials. Analysis of all disease parameters was carried out using SPAD software. There were highly significant differences (Pl0.01) for all disease parameters among the test cultivars. Above half of evaluated Varieties and landraces (57.9 %) showed better Adult plant resistance under high disease pressure. From the total of 235 tested Varieties and landraces, 136 had slow rusting resistance of which 14 were released varieties and the rest 122 were landraces. Four commercial Varieties (Selam, Mossobo, Bekelcha, and Utuba) and a landrace cultivar (Mcd4-32) had high levels of field resistance with very low AUDPC, ACI, and TRS with MR infection type; hence, they may carry major resistance gene (s). However, the rest 99 Varieties and landraces exhibited high to moderate level of slow rusting resistance with MS responses and may have adult plant resistance controlled by minor resistance genes. The slow rusting cultivars identified from the current study can be used for further manipulation in wheat improvement programs.

Pooling together spot blotch resistance, high yield with earliness in wheat for eastern Gangetic Plains of South Asia

This study was done with an objective to attempt to pool together in wheat, the three most important traits (spot blotch resistance, high yield and earliness) for warm humid Eastern Gangetic plains (EGP) of South Asia. A Recombinant Inbred Line (RIL) population, developed from two contrasting parents (YS#58×YS#24) for spot blotch resistance, was tested in seven environments falling under three locations of EGP. Most of the components of variation for three traits were highly significant for each environment as well as in pooled analysis. In general, phenotypic correlation for Area Under Disease Progress Curve (AUDPC) among centers was high and positive. Out of 214 genotypes (211 RILs along with their parents YS#24, YS#58 and Sonalika, check for spot blotch susceptibility and earliness) tested, 15 RILs showed better resistance than the resistant parent. Measured over seven environments, six lines were significantly superior to best check for spot blotch resistance while two for grain yield, four for earliness and two for 1000-grain weight. However, only one line (#94) was found significantly superior for all four traits compared to the best check. Genotype×Environment (G×E) interaction was significant but Genotype×Year (G×Y) was non-significant which indicated the importance of locations for spot blotch. To support this fact, lines superior in one location did not perform well in the other. For resistance, line #174 performed most consistently over 7 environments. Although there was negative correlation between AUDPC and days to heading, low AUDPC was observed in two early maturing RILs (#94 and #1). The study demonstrated that through appropriate crossing and evaluation, it is possible to pool together spot blotch resistance in to high yield back ground of wheat with early maturity.

Reaction of Phaseolus spp. genotypes to ashy stem blight caused by Macrophomina phaseolina

Ashy stem blight (ASB) caused by Macrophomina phaseolina (Tassi) Goidanich (Mp) is a devastating seed-transmitted disease in common bean in the tropics. The identification of resistant cultivars throughout the cropping season contributes to disease management. Resistance is found in the primary and tertiary gene pools. Our objectives were to determine (1) the reaction of Phaseolus spp. genotypes to two Mp isolates at vegetative and reproductive stages, (2) the area under disease progress curve (AUDPC), and (3) resistant plants per genotype at harvest. Twenty-three genotypes from different origins were planted in the greenhouse in 2016 and 2017. One less-aggressive Mp (PRJD16) and one more-aggressive (PRI16) isolate were inoculated one and three times, respectively, by the cut-stem method. ‘Beniquez’, ‘Othello’, and ‘Verano’ were highly susceptible (mean scores >8.0, and AUDPC values from 264.6 to 300.8) to both isolates. BAT 477 and NY6020-4 were intermediate (5.6 and 6.2; AUDPC: 161.6 and 187.1) to PRJD16 and susceptible (7.4 and 8.2; AUDPC: 209.4 and 235.1) to PRI16. Resistant genotypes (mean scores ≤3) were not identified in this study. However, A 195, ‘Badillo’, and ‘PC 50’ possessed lower mean scores (4.3–5.4) and AUDPC values (126.4–150.9) to both isolates. Furthermore, A 195 had the highest percentage of resistant plants (55.6%) followed by PC 50, I9365-31, and PI 321637 (27.8%) to PRJD16 at harvest. Thus, the identification of resistant parents across Phaseolus species is necessary to increase the levels of ASB resistance in common bean cultivars throughout the entire cropping season.

Evaluating Sheath Blight Resistance in Rice Using Detached Tiller and Field Screening Method

In present study physical resistance test on 12 rice varieties against sheath blight (ShB) caused by Rhizoctonia solani was examined. A detached tiller test was used to measure components of ShB physiological resistance at Regional Agricultural Research Station (RARS), Tarahara, Nepal. The varieties were evaluated in a randomized complete block design (RCBD) with 3 replications in year 2010-12. A sclerotium was inserted below the leaf collar of individual tillers maintained in tubes filled with water. Only the 56-day old susceptible plants were inoculated. After 7 days of inoculation, number of lesions, dead leaves, vertical sheath colonization and disease severity were measured. In 2011, field experiments were conducted with three replications to address morphological resistance in 28 rice genotypes. Disease incidence was recorded on 14, 21 and 28 days after inoculation. The number of dead leaves differed only numerically while disease variables significantly (P=0.004) varied among varieties. The other variables were highly correlated with each other. Cluster analysis of variables formed three varietal groups; Sabitri with lowest, and Jasmine-85 and Betichikon having highest values. Rice genotypes differed significantly (P=0.05) for disease incidence and area Under Disease Progress Curve (AUDPC). Tetep and IAC-165 had the lowest and highest terminal disease incidences and AUDPC, respectively. Sabitri, MTU-1010 and IR-26 recorded lower AUDPC values. Hence, Tetep and Sabitri could be used as donors in hybridization and their plant morphology could be considered as selection guide for improving ShB resistance in rice.Journal of Nepal Agricultural Research Council Vol.1 2015 pp.1-8

Biocontrol potential of two novel grapevine associated Bacillus strains for management of anthracnose disease caused by Colletotrichum gloeosporioides

ABSTRACTA study was conducted to identify bacterial antagonists for biological control of anthracnose which is one of the economically important diseases of grapes. In India, it is caused by Colletotrichum gloeosporioides. Two hundred and ninety-three bacteria were isolated from the grape ecosystem of 43 spatially distant vineyards in peninsular India. Of these, 25 bacteria substantially inhibited the radial growth of C. gloeosporioides in in vitro studies and 18 bacteria significantly reduced infections in vivo. Of these 18 bacteria, 5 and 3 bacteria also significantly reduced percent disease index (PDI) of downy and powdery mildew diseases, respectively. These bacteria were labelled as strains, DR-38, DR-39, TL-171, DRo-198, TS-204, TS-205, and DR-219, and were identified as Bacillus species based on morphological and molecular characterisation. Aqueous suspensions of all these strains applied as foliar sprays at 1×108 cfu/ml on field grown vines significantly lowered the PDI and the AUDPC (area under disease progress curve) of anthracnose when compared with the untreated control, except DRo-198. Strains TS-204 and TL-171 recorded lower PDIs and AUDPC when compared with the other five strains, and TS-204 could effectively suppress ripe rot of berries, too, in vivo. Strains TS-204 and TL-171 are identified for biocontrol of anthracnose in grapes.

Genetics of Partial Resistance to Leaf Rust (Puccinia triticina) in Bread Wheat (Triticum aestivum)

The genetics of partial resistance to leaf rust (Puccinia triticina Erikss. & Henn.) in bread wheat (Triticum aestivum L. em Thell) was investigated in a nine-parent diallel (excluding reciprocals) using area under disease progress curve (AUDPC) and final disease severity (FDS) in the F1 and F2 generations. Test material consisted of slow rusting and susceptible lines. The Vr–Wr graphs exhibited partial dominance for FDS and complete dominance for AUDPC (F1 and F2 generations). Parents CPAN1796, HD2329, NW1014 and MACS2496 had preponderance of minor genes for partial resistance, whereas susceptible parents SONALIKA and HS1138-6-4 showed the absence of minor genes for both AUDPC and FDS (F1 and F2 generations). Variations due to additive and dominance genetic variances were significant for both AUDPC and FDS (F1 and F2 generations). The estimate of 1–3 minor gene(s) in the slow rusting parents may be responsible for race non-specific adult plant resistance. Since narrow-sense heritability for both AUDPC and FDS was moderate in both F1 and F2, success in selecting desirable lines with partial resistance to leaf rust in early segregating generations can easily be achieved. The parents CPAN1796, NW1014, HD2329, PBW373 and RAJ3077 with low AUDPC and FDS having partial resistance either due to Lr34 and/or minor genes were identified as good general combiners. The parents identified in the study can be used in breeding program for developing high-yielding cultivars with durable leaf rust resistance.

Effect of silicon on the severity of brown rust of sugarcane in South Africa

Silicon (Si) has been identified as a key element in the management of a wide range of pests and diseases in plants. This study focused on the effect of Si on the severity of brown rust of sugarcane caused by Puccinia melanocephala H & P. Sydow. The trial, repeated twice, consisted of eight treatments which included two different forms of Si and a control to which no Si was added. Plants were naturally infected by spores from brown rust-infected plants within a polytunnel. From three weeks after planting, plants were rated weekly for disease severity and these data were used to calculate an area under disease progress curve (AUDPC). All treatments ≥400 mg Si l−1 had a significantly lower final disease severity rating and AUDPC than the untreated control. No significant difference in disease severity was noted between the 1600 and 2000 mg Si l−1 treatments. A once off application of calcium silicate at a concentration of 1016 mg Si l−1, applied at planting provided the same reduction in disease severity as K2SiO3 applied weekly at a Si concentration of 1200 mg Si l−1. There was a significant negative relationship between the concentration of Si added and disease severity. A similar relationship was noted for the disease severity index and Si accumulation and deposition in the leaf. Results from this study showed a reduction in brown rust severity with an increase in Si content in the plant.

Biological control of Verticillium wilt of olive by Paenibacillus alvei, strain K165

In the present study, the efficiency of the biocontrol agent Paenibacillus alvei (strain K165) to suppress Verticillium wilt of olive tree was evaluated in greenhouse and field experiments. In planta bioassays were conducted under greenhouse conditions and revealed that K165 significantly decreased symptoms on the susceptible cultivar ‘Amfissis’ by 44.5 and 51.6 % of the final disease severity index and relative area under disease progress curve (AUDPC), respectively. Thereafter, the suppressive effect of K165 against Verticillium dahliae was studied for two consecutive years (2007 and 2008) in a newly established olive orchard of the susceptible cv Amfissis and the resistant cv Kalamon, naturally infested with V. dahliae. The evaluation of K165 was carried out by recording symptoms, isolations and qPCR quantification of the pathogen in olive tissues. In both years, ‘Amfissis’ trees treated with K165 showed significantly lower final disease severity and relative AUDPC values compared to the non treated controls, whereas, in 2008 decreased symptom severity was associated with significantly lower V. dahliae DNA levels in plant tissues, indicating the suppressive effect of the biocontrol agent. However, no significant suppression was observed in ‘Kalamon’. Pathogen isolations along with qPCR quantification revealed a seasonal fluctuation of V. dahliae biomass in olive tissues with higher amounts occurring in May, and lower amounts in February, August and November. This is the first report of biological control of Verticillium wilt of olive tree under field conditions, associated with reduced pathogen levels inside the xylem tissues.

Use of four Sclerotinia sclerotiorum isolates of different aggressiveness, three inoculations per plant, and delayed multiple evaluations to select common beans with high levels of white mold resistance

White mold is a severe disease of common bean worldwide. Partial resistance occurs in the primary and secondary gene pools. Factors essential for identifying high levels of resistance that is effective throughout the growing season are not known. Our objectives were to determine which factors are most essential for identifying high levels of resistance including: (i) pathogen isolates screened, (ii) inoculations/plant, (iii) evaluation dates, (iv) area under disease progress curve (AUDPC), and (v) the SCAR markers linked with WM2.2, WM6.1, WM7.1, WM7.3, and WM8.3 resistance QTL. Thirty-one genotypes were inoculated one to three times/plant with ARS12D and ND710 isolates in the greenhouse in Idaho, and CO467 and NY133 in Colorado. Evaluations were made from 7 to 35 days post-inoculation. Disease severity and AUDPC increased until 21 days in Colorado and 35 days in Idaho. Correlations were positive among isolates at each evaluation date. The presence or absence of white mold resistance QTL was not indicative of resistance response. ‘Othello’ was susceptible to all isolates with one inoculation, and VC13-5 was resistant to three isolates and intermediate to ND710 after three inoculations per plant; both of these genotypes lacked the five resistance QTL. SE155-9 with WM2.2, WM7.1, and WM8.3 QTL was resistant to CO467 and NY133. However, SE152-6 with the same QTL was resistant and possessed lower AUDPC values to all isolates after three inoculations. Thus, screening with four isolates, three inoculations/plant, and disease evaluations delayed until 21 days or longer helped identify genotypes with high levels of broad-spectrum resistance.

Methods and Evaluation of Soybean Genotypes for Resistance to Colletotrichum truncatum.

Anthracnose of soybean (Glycine max) occurs throughout the soybean production areas of the world. There is little information on evaluating inoculation techniques or evaluating soybean germplasm for resistance. The objectives of this study were to develop a reliable inoculation technique for evaluating soybean for resistance to Colletotrichum truncatum and to evaluate soybean genotypes for resistance. Inoculated plants incubated in a dew chamber for 48 or 72 h had higher (P = 0.05) area under disease progress curve (AUDPC) values than when incubated for 24 h. Three experiments evaluated soybean genotypes for resistance to C. truncatum. In the first experiment using 15 soybean genotypes, 'Mandarin' had lower (P = 0.05) AUDPC values than all the other genotypes except for 'Mandarin 507', 'Mandarin (Ottawa)', and 'Boone'. In the second experiment using 28 soybean genotypes, Mandarin 507 had lower (P = 0.05) AUDPC values compared with all other soybean genotypes except 'Early White Eyebrow', 'Mandarin Yowa', Boone, and 'Manchuria'. In the third experiment, Mandarin 507 had lower (P = 0.05) AUDPC values compared with 23 other soybean genotypes except 'Spry', Mandarin, and 'Iroquois'. Plants of Mandarin 507 and 'Williams 82' were inoculated at the vegetative and reproductive growth stages; Mandarin 507 had lower (P = 0.05) AUDPC values compared with Williams 82 for both growth stages evaluated, and Mandarin 507 had less (P = 0.05) pod area covered by lesions compared with the pods of Williams 82. This study provided a descriptive method to inoculate soybean plants with C. truncatum and identified soybean genotypes with resistance to anthracnose.

Genetics of Partial Resistance to Leaf Rust (<i>Puccinia triticina</i> Erikss. & Henn.) in Bread Wheat (<i>Triticum aestivum</i> L. em Thell)

The genetics of partial resistance to leaf rust ( Puccinia triticina Erikss. & Henn.) in bread wheat ( Triticum aestivum L. em Thell) was investigated in a nine-parent diallel (excluding reciprocals) using area under disease progress curve (AUDPC) and final disease severity (FDS) in the F 1 and F 2 generations. Test material consisted of slow rusting and susceptible lines. The Vr-Wr graphs exhibited partial dominance for FDS and complete dominance for AUDPC (F 1 and F 2 generations). Parents CPAN1796, HD2329, NW1014 and MACS2496 had preponderance of minor genes for partial resistance, whereas, susceptible parents SONALIKA and HS1138-6-4 showed absence of minor genes for both AUDPC and FDS (F 1 and F 2 generations). Variations due to additive and dominance genetic variances were significant for both AUDPC and FDS (F 1 and F 2 generations). The estimate of 1-3 minor gene(s) in the slow rusting parents may be responsible for race non-specific adult plant resistance. Since narrow sense heritability for both AUDPC and FDS, was moderate in both F 1 and F 2 , success in selecting desirable lines with partial resistance to leaf rust in early segregating generations can easily be achieved. The parents CPAN1796, NW1014, HD2329, PBW373 and RAJ3077 with low AUDPC and FDS having partial resistance either due to Lr34 and/ or minor genes were identified as good general combiners. The parents identified in the study can be used in breeding program for developing high yielding cultivars with durable leaf rust resistance.

Sustainable yield: The contribution of modern breeding and biotechnology in helping farmers increase yield and reduce environmental impacts in Asia

Yellow mosaic disease (YMD) of black gram is an important production constraint in India. Black gram germplasm, consisting of 344 accessions, originally collected from different geographic regions of India and conserved in National Gene Bank at National Bureau of Plant Genetic Resources, India, were evaluated for their response against YMD. None of the accessions tested was found to be immune, however, considerable variation in disease response was observed among them. Of the 344 accessions, 32 showed resistance in the field during the rainy season (June–September) 2010 as assessed by coefficient of infection (CI) and area under disease progress curve (AUDPC). These accessions were re-evaluated during rainy season (June–September) 2011 and 2012 for their disease resistance along with yield-associated characters. Eight accessions that exhibited consistently highly resistant (HR) or resistant (R) reaction (CI ≤ 9) along with lower AUDPC value (≤650), were further evaluated following inoculation with whiteflies or via agroinoculation. Along with the resistant trait, these eight accessions were also found either similar or even better in their yield potential as compared to check. After artificial inoculation using viruliferous whiteflies under glasshouse, of the eight field-resistant accessions, response of two (IC144901 and IC001572) were categorized as HR as <10% plants exhibited minute yellow specks after 17–22 dpi. Two accessions viz. IC011613 and IC485638 showed <20% incidence with bright yellow specks or spots after 15–20 dpi and were grouped into R category. The resistance of these four accessions was further confirmed through agroinoculation of the infectious cloned viral DNA under controlled conditions. In resistant accessions low accumulation of viral DNA was observed over a period of time. These four accessions could be used in future breeding programmes to develop black gram cultivars resistant to YMD or could be used directly as varieties to manage YMD after adaption to various agro-climatic regions.

Evaluation of an Indian collection of black gram germplasm and identification of resistance sources to Mungbean yellow mosaic virus

Yellow mosaic disease (YMD) of black gram is an important production constraint in India. Black gram germplasm, consisting of 344 accessions, originally collected from different geographic regions of India and conserved in National Gene Bank at National Bureau of Plant Genetic Resources, India, were evaluated for their response against YMD. None of the accessions tested was found to be immune, however, considerable variation in disease response was observed among them. Of the 344 accessions, 32 showed resistance in the field during the rainy season (June–September) 2010 as assessed by coefficient of infection (CI) and area under disease progress curve (AUDPC). These accessions were re-evaluated during rainy season (June–September) 2011 and 2012 for their disease resistance along with yield-associated characters. Eight accessions that exhibited consistently highly resistant (HR) or resistant (R) reaction (CI ≤ 9) along with lower AUDPC value (≤650), were further evaluated following inoculation with whiteflies or via agroinoculation. Along with the resistant trait, these eight accessions were also found either similar or even better in their yield potential as compared to check. After artificial inoculation using viruliferous whiteflies under glasshouse, of the eight field-resistant accessions, response of two (IC144901 and IC001572) were categorized as HR as <10% plants exhibited minute yellow specks after 17–22 dpi. Two accessions viz. IC011613 and IC485638 showed <20% incidence with bright yellow specks or spots after 15–20 dpi and were grouped into R category. The resistance of these four accessions was further confirmed through agroinoculation of the infectious cloned viral DNA under controlled conditions. In resistant accessions low accumulation of viral DNA was observed over a period of time. These four accessions could be used in future breeding programmes to develop black gram cultivars resistant to YMD or could be used directly as varieties to manage YMD after adaption to various agro-climatic regions.