Plant Pathology

EPIDEMIOLOGY OF GRAY LEAF SPOT (CERCOSPORA ZEAE- MAYDIS) AND GENETICS OF RESISTANCE IN MAIZE TO THE DISEASE IN ETHIOPIA

Thu, 01 Mar 2018 00:00:00 GMT

EPIDEMIOLOGY OF GRAY LEAF SPOT (CERCOSPORA ZEAE- MAYDIS) AND GENETICS OF RESISTANCE IN MAIZE TO THE DISEASE IN ETHIOPIA Zelalem Bekeko Erena; Prof. Chemeda Fininsa; Prof. Temama Hussien; Prof.Shimelis Hussie Maize (Zea mays L.) is an important component of farming systems and staple food crop in sub- Saharan Africa. In Ethiopia it is a staple food crop and one of the main sources of calories in the major maize producing regions. It is cultivated on about 2.135 million hectares of land. The national average yield of maize under subsistence production is 3667.5kg/ha. This is too much below the world’s average yield which is over 6520 kg/ha. This low yield is attributed to several factors among which foliar diseases and insect pests are the major once. Gray leaf spot (GLS) caused by the pathogen Cercospora zeae-maydis is one of the necrotrophic and polycyclic foliar diseases of maize that poses a serious problem to maize production and productivity in Ethiopia. Field surveys were conducted in Western and South western parts of the Oromia National Regional State, Ethiopia during 2015 and 2016 main cropping seasons to determine the distribution, prevalence, importance and the association of gray leaf spot (Cercospora Zeae maydis) epidemics with environmental factors and cultural practices. In both years a total of 480 maize fields were surveyed in four zones and 90% of the fields were infested with gray leaf spot. Gray leaf spot incidence and severity varied among zones, between years, altitude range, soil types and field management practices. The mean disease incidence in 2 years ranged from 35% in Horro Guduru to 95% in Jimma zone and severity ranged from 25% in west Shewa to 75% at Jimma and East Wollega zones where it was significantly higher. The incidence in 2016 cropping season was higher by 55% than in 2015. Logistic regression was used to analyze the association of gray leaf spot incidence and severity with environmental factors and cultural practices as independent variables. Analysis of result (p=0001) showed Zones, varieties, cropping year, soil type, maize crop residues and weed management practices were significantly associated with gray leaf spot incidence and severity in a multiple variable model. Higher incidence of gray leaf spot was significantly associated with east Wollega and Jimma zones, crop residue, rain fall and sowing dates. Lower incidences had a high probability of association with Horro Guduru and west Shewa in (2015) cropping year and good weed management practices. In a reduced multiple variable xiv model, sowing date, variety, area, year, weed management practices and tillage frequency were significantly associated with higher gray leaf spot incidence and severity. Increased incidence was observed in maize intercropped with haricot bean than brassica spps. The survey revealed high occurrence and distribution of gray leaf spot in the study area. Thus, effective and feasible management options need to be developed in combating this foliar disease of maize. In experiment two fourteen advanced maize inbred lines and locally adapted hybrid maize (BH-540) as a check were used to investigate their reaction to GLS disease. Field experiments were conducted at Bako National Maize Research Centre in 2015 and 2016 main planting seasons arranged in a randomized complete block design (RCBD) with three replications. Artificial inoculation with Cercospora zeae-maydis was conducted by applying dry, ground, infected maize leaves into the whorls of younger maize plants. Data on agronomic and disease parameters (latent period, disease severity, disease incidence and lesion type) were recorded from the middle two rows. From the combined analysis of variance, maize genotypes showed significant differences with reaction to GLS indicating the existence of genetic variability among the selected genotypes. Highly significant differences were also observed among entries for all agronomic parameters in both seasons. Gray leaf spot incidence and severity varied among genotypes and between years. The mean GLS incidence and severity were higher in 2016 than 2015. GLS disease incidence in two years ranged from 35% on Sc22 to 95% on CML-387 and severity ranged from 15% on A-7016 to 75% on CKL05003. Significant differences in epidemic variability were also observed among genotypes and seasons. From the analysis of disease progress curves Logistic model (R2=94.55) better described the disease progress curves than the Gompertz model (R2=91.50). Parents; P6 and P8 had the most desirable quality for the most of agronomic traits whereas P2, P7 and P9 were the best parents for grain yield. Among all inbred lines, P6, P7 and P14 were identified as the most desirable sources of genes for GLS disease resistance. But P6, P7, P8 and P14 were identified as the best genotypes in 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 disease resistant open pollinated varieties. In conclusion this study identified potential and promising high yielding and GLS resistant open pollinated genotypes (CKL05017-B-B, CML-395, CML-387, A-7016, Gutto and Sc22). Therefore, it is recommended that these OPVs can be used by resource poor farmers for direct production where this disease is the most prevalent and/or for further breeding programs in generating novel hybrids for future use. Similarly in experiment three 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 x 10 half-diallel mating design to produce 45 F1 single cross hybrids. The experiment was conducted at Bako national maize research center in xv 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. Artificial inoculation with Cercospora zeae-maydis was conducted by applying dry, ground, infected maize leaves into the whorls of younger maize plants. 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. P3 and P4 had the most desirable quality for most agronomic traits whereas P2, P7 and P9 were the best combiners for grain yield with the general combining ability (GCA) effects of 0.80, 0.75 and 1.56 respectively. 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. Some of the cross combinations showed significant SCA effects, suggesting that these crosses have performed significantly higher or lower than what was predicted based on their parental performances implying the importance the non additive gene action. 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 disease. 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 disease resistant single cross hybrids. In conclusion this study identified potential high yielding and GLS resistant single cross hybrids (CML-395/ CML383, CML395/Sc22, 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 141p.

EPIDEMIOLOGY OF GRAY LEAF SPOT (CERCOSPORA ZEAE- MAYDIS) AND GENETICS OF RESISTANCE IN MAIZE TO THE DISEASE IN ETHIOPIA

Thu, 01 Mar 2018 00:00:00 GMT

EPIDEMIOLOGY OF GRAY LEAF SPOT (CERCOSPORA ZEAE- MAYDIS) AND GENETICS OF RESISTANCE IN MAIZE TO THE DISEASE IN ETHIOPIA Zelalem Bekeko Erena; Prof Chemeda Fininsa; Professor Shimelis Hussien; Dr. Dagne Wegari; Dr. Belachew Asal Maize (Zea mays L.) is an important component of farming systems and staple food crop in sub- Saharan Africa. In Ethiopia it is a staple food crop and one of the main sources of calories in the major maize producing regions. It is cultivated on about 2.135 million hectares of land. The national average yield of maize under subsistence production is 3667.5kg/ha. This is too much below the world’s average yield which is over 6520 kg/ha. This low yield is attributed to several factors among which foliar diseases and insect pests are the major once. Gray leaf spot (GLS) caused by the pathogen Cercospora zeae-maydis is one of the necrotrophic and polycyclic foliar diseases of maize that poses a serious problem to maize production and productivity in Ethiopia. Field surveys were conducted in Western and South western parts of the Oromia National Regional State, Ethiopia during 2015 and 2016 main cropping seasons to determine the distribution, prevalence, importance and the association of gray leaf spot (Cercospora Zeae maydis) epidemics with environmental factors and cultural practices. In both years a total of 480 maize fields were surveyed in four zones and 90% of the fields were infested with gray leaf spot. Gray leaf spot incidence and severity varied among zones, between years, altitude range, soil types and field management practices. The mean disease incidence in 2 years ranged from 35% in Horro Guduru to 95% in Jimma zone and severity ranged from 25% in west Shewa to 75% at Jimma and East Wollega zones where it was significantly higher. The incidence in 2016 cropping season was higher by 55% than in 2015. Logistic regression was used to analyze the association of gray leaf spot incidence and severity with environmental factors and cultural practices as independent variables. Analysis of result (p=0001) showed Zones, varieties, cropping year, soil type, maize crop residues and weed management practices were significantly associated with gray leaf spot incidence and severity in a multiple variable model. Higher incidence of gray leaf spot was significantly associated with east Wollega and Jimma zones, crop residue, rain fall and sowing dates. Lower incidences had a high probability of association with Horro Guduru and west Shewa in (2015) cropping year and good weed management practices. In a reduced multiple variable xiv model, sowing date, variety, area, year, weed management practices and tillage frequency were significantly associated with higher gray leaf spot incidence and severity. Increased incidence was observed in maize intercropped with haricot bean than brassica spps. The survey revealed high occurrence and distribution of gray leaf spot in the study area. Thus, effective and feasible management options need to be developed in combating this foliar disease of maize. In experiment two fourteen advanced maize inbred lines and locally adapted hybrid maize (BH-540) as a check were used to investigate their reaction to GLS disease. Field experiments were conducted at Bako National Maize Research Centre in 2015 and 2016 main planting seasons arranged in a randomized complete block design (RCBD) with three replications. Artificial inoculation with Cercospora zeae-maydis was conducted by applying dry, ground, infected maize leaves into the whorls of younger maize plants. Data on agronomic and disease parameters (latent period, disease severity, disease incidence and lesion type) were recorded from the middle two rows. From the combined analysis of variance, maize genotypes showed significant differences with reaction to GLS indicating the existence of genetic variability among the selected genotypes. Highly significant differences were also observed among entries for all agronomic parameters in both seasons. Gray leaf spot incidence and severity varied among genotypes and between years. The mean GLS incidence and severity were higher in 2016 than 2015. GLS disease incidence in two years ranged from 35% on Sc22 to 95% on CML-387 and severity ranged from 15% on A-7016 to 75% on CKL05003. Significant differences in epidemic variability were also observed among genotypes and seasons. From the analysis of disease progress curves Logistic model (R2=94.55) better described the disease progress curves than the Gompertz model (R2=91.50). Parents; P6 and P8 had the most desirable quality for the most of agronomic traits whereas P2, P7 and P9 were the best parents for grain yield. Among all inbred lines, P6, P7 and P14 were identified as the most desirable sources of genes for GLS disease resistance. But P6, P7, P8 and P14 were identified as the best genotypes in 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 disease resistant open pollinated varieties. In conclusion this study identified potential and promising high yielding and GLS resistant open pollinated genotypes (CKL05017-B-B, CML-395, CML-387, A-7016, Gutto and Sc22). Therefore, it is recommended that these OPVs can be used by resource poor farmers for direct production where this disease is the most prevalent and/or for further breeding programs in generating novel hybrids for future use. Similarly in experiment three 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 x 10 half-diallel mating design to produce 45 F1 single cross hybrids. The experiment was conducted at Bako national maize research center in xv 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. Artificial inoculation with Cercospora zeae-maydis was conducted by applying dry, ground, infected maize leaves into the whorls of younger maize plants. 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. P3 and P4 had the most desirable quality for most agronomic traits whereas P2, P7 and P9 were the best combiners for grain yield with the general combining ability (GCA) effects of 0.80, 0.75 and 1.56 respectively. 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. Some of the cross combinations showed significant SCA effects, suggesting that these crosses have performed significantly higher or lower than what was predicted based on their parental performances implying the importance the non additive gene action. 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 disease. 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 disease resistant single cross hybrids. In conclusion this study identified potential high yielding and GLS resistant single cross hybrids (CML-395/ CML383, CML395/Sc22, 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 141p.

EVALUATION OF POTATO GENOTYPES TO REDEPLOYMENT FOR LATE BLIGHT (Phytophthora infestans) RESISTANCE AND AGRONOMIC PERFORMANCES AT HARAMAYA, ETHIOPIA

Tue, 01 Feb 2022 00:00:00 GMT

EVALUATION OF POTATO GENOTYPES TO REDEPLOYMENT FOR LATE BLIGHT (Phytophthora infestans) RESISTANCE AND AGRONOMIC PERFORMANCES AT HARAMAYA, ETHIOPIA Habtamu W/Michael Shomore; Habtamu Terefe (PhD; Prof. Wassu Mohammed (PhD)________ Late blight, caused by Phytophthora infestans,isa major threat of potato production and productivity worldwide, including Ethiopia. The pathogen has the ability to rapidly evolve and the resistantvarieties become susceptible soon after their release. Thus, screening of large set of potato genotypes to late blight resistance is vital to sustain the productivity of the crop. This research was conducted with the objective to evaluate and estimate genetic variability of potato genotypes for late blight resistance and morpho-agronomic traits, and determine the association of tuber yield, yield-related traits and genotypes reaction to late blight disease. 68 genotypes were evaluated in augmented design with eight blocks at Raare research field of Haramaya University in 2021. Results revealed that genotypes showed significant differences for all traits, except number of leaves and main stems. The test genotypes and check varieties (Bubu, Belete, Gudanie, and Jarso)had also significant differences for all traits, except days of late blight appearance, days to maturity, and average tuber weight. The total (TTY) and marketable (MTY) tuber yield of genotypes ranged between 10.66 and 33.80 t ha–1, and 9.93 and 31.97 t ha–1, respectively. The best performing check variety Belete had 25.21and 21.67 t ha–1TTY and MTY, respectively, and CIP- 388370-12B, CIP-386029-10A, Al-667, CIP-392640-541, CIP-388370-12A, CIP-90162-3, CIP- 383032-15, AL-560, Al-436-1, Al-624-33, Al-624-9, CIP-377838-12, Al-601, CIP-391058-558, CIP-396036-201, and CIP-395017-242 new entries produced higher TTY and MTY than the best performing check variety. Late blight appeared early at 43 days after planting (DAP) on Jarso farmers cultivar and late at 59 DAP on CIP-377808-10A. Percent severity index (PSI) and area under disease progress curve (AUDPC) ranged from 31.45 to 100% and 569.23 to 1704.79%-days in that order. Disease progress rate (r) ranged between 0.024 and 0.158 units day–1. Bubu,and Belete varieties and other 16 genotypes showed moderate resistance to late blight, and reported as MR to late blight. The PSI and AUDPC had negative and significant genotypic correlation coefficient with days to maturity, plant height, average tuber weight, TTY and MTY, but had positive and significant genotypic correlation coefficient with unmarketable tuber yield. Phenotypic and genotypic coefficients of variation ranged from 2.38 to 48.73% and 1.71 to 15.8%, respectively, whereas heritability in broad sense and genetic advance as percent of the mean ranged from 10.52 to 96.5% and 2.49 to 28.8% in that order of presentation. The first principal component (PCs) axis explained 71.67% of genetic variation; of which, PC1 had the largest share of 45.48%. Total and marketable tuber yields, PSI and AUDPC in PC1, unmarketable tuber yield in PC2 and number of tubers per hill in PC3 had the largest contribution. The Euclidean distances (D2) of all possible pairs of genotypes ranged from 0.80 to 9.2 and based on D2 matrix, the 68 genotypes were with the mean, standard deviation and coefficient of variation having the values of 4.44, 1.52 and 34.28%, respectively.Genotypes were clustered based on D2, and cluster I consisted of 31(45.58%) genotypes and the other eight clusters consisted of 1 to 9 genotypes. MR varieties (Bubu and Belete) were grouped in Cluster I. The mean of genotypes in this cluster was greater than grand mean of genotypes for agronomic traits but had PSI and AUDPClower mean than mean of genotypes. This suggested further evaluation of genotypes in Cluster I to develop varieties resistant to late blight and high yield.The PSI and AUDPC had high heritability coupled with high genetic advance suggested selection of genotypes based on phenotypic observation was efficient.This indicated not only from recently developed genotypes but also there is the high chance of selection of resistant genotypes produced before 35 years from true potato seed. Therefore, the 16 genotypes exhibited lower disease severity (moderately resistant), so that these genotypes could be recommended for cultivation and further breeding utilization 130

RESPONSE OF BREAD WHEAT (Triticum aestivum L.) GENOTYPES TO YELLOW RUST (Puccinia striiformis f. sp. tritici) AT SEEDLING AND ADULT PLANT STAGES IN BALE HIGHLANDS, SOUTHEASTERN ETHIOPIA

Thu, 01 Jun 2023 00:00:00 GMT

RESPONSE OF BREAD WHEAT (Triticum aestivum L.) GENOTYPES TO YELLOW RUST (Puccinia striiformis f. sp. tritici) AT SEEDLING AND ADULT PLANT STAGES IN BALE HIGHLANDS, SOUTHEASTERN ETHIOPIA Mohammedamin Abdurezake Bedri Wheat is one of the most important strategic crops in the world. However, its production and productivity is constrained by both biotic and abiotic factors. Of the biotic factors, wheat yellow rust is the most devastating disease of wheat. Hence, seeking new sources of resistance is prominent to manage the disease for sustaining wheat production. The current study was conducted to determined the response, the sources of resistance of bread wheat genotypes against yellow rust at seedling and adult plant stages and to evaluate the direct and indirect effects of yield components on grain yield at Sinana and Agarfa research sites in Bale highlands for field and at Kulumsa Agricultural Research Center for greenhouse experiment. A total of 64 bread wheat genotypes including three checks (Boru ,Hachalu and Maddawalabu) were laid out in a simple alpha design for field experiment. The same genotypes in the field and universal susceptible variety (Morocco) were used in the greenhouse. The seedlings were inoculated with five different isolates received from KARC following the standard procedures to evaluate the tested genotypes. The analysis of variances showed highly significant differences (P<0.001) for all traits among tested genotypes. In general, the value of phenotypic coefficient of variation was higher than genotypic coefficient of variation for all studied traits indicating that the higher variability existing among wheat genotypes. Correlation analysis also showed significant associations among tested traits at both genotypic and phenotypic level. Biomass yield and thousand kernels weight at genotypic, and biomass yield and plant height at phenotypic level were exerted the highest direct effect on the grain yield. There were highly significant differences (P<0.001) among tested bread wheat genotypes for disease parameters (final rust severity, head infection, area under disease progress curve, relative area under disease progress curve and coefficient of infection ) at both locations. The identified resistant genotypes at adult plant and seedling stages can be used as resistance sources and exploited in breeding program for wheat yield improvement. 106