Diversity of the Rice Blast Pathogen Populations in Ghana and Strategies for Resistance Management

The present study describes the outputs of a collaborative research programme funded by the UK`s Department for International Development-Crop Protection Program to investigate the genetic (lineages) and pathogenic (pathotypes) diversity of the blast fungus populations and characterize the key sites suitable for resistance screening. Seventy-one Magnaporthe grisae isolates were collected from seven regions where rice is grown, representing blast populations in Ghana. Following molecular characterization, these isolates were grouped into four distinct lineages designated as GH-1, GH-2, GH-3 and GH-4 and 25 pathotypes. GH-1 was the major lineage comprising 52% of all the isolates and was present across the country on up to 24 rice cultivars. GH-2 comprising of 30% of the isolates sampled was restricted in distribution mainly from Hohoe area on up to seven cultivars. GH-3 consisted of six isolates from Western, Eastern and Central Regions while GH-4 consisted of two isolates from Nyankpala in Northern Region. Occurrence of blast pathogen on wild rice and weed hosts has been observed and their potential impact needs to be considered in blast/weed management. Baseline data new to Ghana on the diversity and distribution pattern of the blast pathogen populations have been established and key sites identified. Adaptive research is continuing to develop technologies suitable for long-term pathogen monitoring, identify sources of resistance and develop appropriate blast management strategies

Assessment of yield losses due to early and late leaf spots of groundnut (Arachis hypogaea L.)

Early leaf spot (Cercospora arachidicola) and late leaf spot (sporidium personatum) are major limiting factors to groundnut productivity in northern Ghana. Fourteen groundnut entries were evaluated for two seasons (2003 and 2004) at Nyankpala with and without tebuconazole fungicide application. The objective of this study was to determine the yield losses due to combined attack of both diseases, with and without using tebuconazole (Folicur 3.6F) at 0.22 kg a.i. ha-1. The experiments were established in a split-plot design with three replications. Disease rating and pod yield were recorded at harvest maturity. Yield losses varied considerably, depending on entry and its yield potential. Pod yield losses due to both diseases ranged from 9.7 to 81.2 per cent in 2003, and from 19.5 to 65.9 per cent in 2004 when yield of protected entries was compared with yield of unprotected entries. The application of fungicide was effective in controlling leaf spots and improved pod yields across the two seasons. Some entries treated with fungicide produced pod yield of 1,860 to 2,081 kg ha-1, which is more than 2 to 2½-fold increase over present average yields in Ghana. Based on the high yield losses, chemical control and host-plant resistance options for managing both diseases in the north are recommended to enhance groundnut production. La tache à feuilles précoce (Cercospora arachidicola) et la tache à feille tardice (Cercosporidium personatum) sont des facteurs contraignants majeurs à la productivité d\'arachide dans le nord du Ghana. Quartorze variétés d\'arachide étaient évaluées pour deux saisons (2003 et 2004) à Nyankpala avec ou sans application de fongicide. Le but de ce travail de recherche était de déterminer les pertes de rendement en raison d\'attaque combinée des deux maladies en utilsant tébuconazole (Folicur 3.6F) à 0.22 kg a. i./ha. Les expériences étaient étabiles dans un dessin de lot-divisé avec trois répétitions. L\'indice de maladie et le rendement de cosse dues aux deux maladies variant entre 9.7 et 81.2% en l\'année 2003 et entre 19.5 et 65.9% en l\'année 2004 lorsque le rendment des varétés protégées avec fongicide était comparé avec le rendement des variétés non protégées. Application de fongicide était efficace dans la lutte contre les taches à feuille et améliorait également les rendements de cosse au cours de deux saisons. Quelques variétés traitées de fongicide donnaient un rendement de cosse de 1,860 à 2,081 kg/ha qui est plus 2 ou 2½ fois d\'augmentation par rapport aux randements moyens actuels au Ghana. Fondé sur les pertes de tendement élevées, l\'enrayement chimique et les options de plante-hôte résistante sont recommandés pour la lutte contre les deux maladies dans le nord afin d\'améliorer la production d\'arachide. Ghana Journal of Agricultural Science Vol. 40 (1) 2007: pp. 21-2

Adoption of rice cultivation technologies and its effect on technical efficiency in Sagnarigu District of Ghana

This study examined the adoption of rice cultivation technologies on farmers’ technical efficiency in Sagnarigu District. The stochastic frontier model was used to estimate the determinants of output and technical inefficiency while propensity score matching was also used to analyse the average treatment effect (ATE) and the average treatment effect on the treated (ATT). A total of 120 respondents comprising 60 adopters and 60 non-adopters were randomly selected from six communities in the District and interviewed using semi-structured questionnaires. Farm size, fertilizer, weedicides and household labour had positive and significant effect on rice output. Farmers who adopted the rice cultivation techniques were less technically inefficient than those who did not adopt. The ATT was 0.121 which implies that farmers who adopted the rice technologies increased their technical efficiency by about 12% and this was significant at 10% for the PSM with similar results obtained for the nearest neighbour matching. The ATE value of 0.102 which was also statistically significant at 10% means that farmers on the whole increased their technical efficiency by 10.2%. Moreover, the mean technical efficiency estimates for adopters and non-adopters were about 58% and 48% respectively under regression adjustment and inverse-probability weights. The existence of a technical efficiency gap of 10% between adopters and non-adopters of rice technologies emphasized the significant effect of technology adoption on farmer’s technical efficiency. The study recommends that more rice farmers should be encouraged to adopt the rice production technologies in order to improve their technical efficiency levels

Evaluation of Pearl Millet for Yield and Downy Mildew Resistance across Seven Countries in Sub-Saharan Africa

Forty pearl millet germplasms consisting of traditional and improved open pollinated varieties, hybrids, and inbreds were selected to represent diversity for grain yield or quality, fertility restoration for specific cytoplasms, resistance to diseases or pests, variation in height and maturity, and origin. Evaluations were conducted in field trials in Ghana, Mali, Nigeria, and Senegal in 2003 and 2004 and in Burkina Faso, Niger, and Zambia in 2004. Data were collected on yield, downy mildew incidence, maturity, plant height, and panicle length. Variation occurred for all traits across locations and genotypes. Across locations and years, Sosat-C88, ICMV IS 89305, Gwagwa, NKK, Sosank, and CIVT were the highest yielding entries. Yields of Sosat-C88, Sosank, and CIVT were more stable across environments, and yields of ICMV IS 89305, Gwagwa, and NKK increased in response to more favorable environments. Sosank, CIVT, ICMV IS 89305, Sosat-C88, and Gwagwa were also among the most downy mildew resistant entries. Across locations and years, grain yield was negatively correlated with downy mildew incidence, and positively correlated with days to flowering, plant height, and panicle length. These correlations differed among some of the individual trials, with days to flowering having the least consistent correlations with grain yield. Further selection for improved yield and broad adaptation in pearl millet is likely to be possible, however, site-specific selection is necessary to identify other important traits in addition to yield. The high-yielding and downy mildew resistant pearl millets identified in this study will be useful to introgress new traits into preferred local varieties, or to serve as parental material for breeding and hybrid development

Prevalence of rice blast and varietal screening in Ghana

Surveys were conducted in farmers' fields, participatory varietal selection (PVS) nurseries and researchers' fields during 2000-2002 cropping seasons to assess the incidence of rice blast (Pyricularia oryzae) in Ghana. Screenhouse artificial inoculation studies and field trials were also carried out on some of the rice varieties to assess their response to blast. Blast was recorded in 264 fields in the countrywide surveys. The incidence of blast varied considerably across the country and areas of blast scores of 0-3 (low), 4-6 (moderate) and 7-9 (high) have been identified. No blast was observed in Brong Ahafo, Greater Accra and Upper West Regions. Farmers at some of the high blast areas notably Fodome, Hohoe, Santrokofi and Datano reported complete devastation of their rice fields due to blast infection. The survey results suggest that Datano, Hohoe and Nyankpala are blast prone areas and key sites for resistance screening. The PVS rice varieties, with a few exceptions, had low blast severity scores at the key screening sites under natural field conditions, while the improved varieties had shown varying degrees of resistance to the dominant Ghanaian blast lineage representatives under screenhouse conditions. These improved varieties need to be tested sufficiently at other major rice-growing areas across the country to benefit the low-resourced farmers where improved varieties are not available or where local varieties are susceptible to the blast disease. Journal of Science and Technology Vol. 25(2) 2005: 18-3

Groundnut yields response and economic benefits of fungicide and phosphorus application in farmer-managed trials in northern Ghana

Citation: Naab, J. B., S. S. Seini, K. O. Gyasi, G. Y. Mahama, P. V. V. Prasad, K. J. Boote, and J. W. Jones. “GROUNDNUT YIELD RESPONSE AND ECONOMIC BENEFITS OF FUNGICIDE AND PHOSPHORUS APPLICATION IN FARMER-MANAGED TRIALS IN NORTHERN GHANA.” Experimental Agriculture 45, no. 4 (October 2009): 385–99. https://doi.org/10.1017/S0014479709990081.Prior on-station research showed that sowing dates, sowing density and applications of fungicide and phosphorus (P) increased groundnut (Arachis hypogaea) pod yield by 60–80%. Farmer-managed trials were conducted in the Wa district of the Upper West Region of Ghana from 2004 to 2007 to test the yield response to sowing density, fungicide and P and to assess economic returns of these technologies to farmers. Treatments included: an early maturing groundnut cultivar, Chinese, sown at farmers’ density (5–8 plant m−2) without fungicide and without P application (T1, control), with fungicide sprays alone (T2), or with fungicide and P application (T3), cultivar Chinese sown at recommended (higher) density (20 plant m−2) with fungicide and P application (T4), and a full season cultivar, Manipinter, with fungicide and P application (T5). Soil fertility, sowing density, days from sowing to first weeding, incidence and severity of leaf-spot disease and plant population at final harvest were recorded. Relative to farmers’ practice, pod yield of cultivar Chinese was significantly increased by 80% with fungicide sprays alone, 108% with fungicide and P application, and 113% with fungicide and P application at higher sowing density. Cultivar Manipinter treated with fungicide and P gave 107% increase in pod yield relative to farmers’ practice. Correlation and stepwise regression analyses suggested that major determinants of groundnut pod yield in farmers’ fields were plant density, leaf-spot disease and P availability. The increase in yield with fungicide and P application translated into a 4–5-fold increase in gross margin for farmers in the region. Returns to labour and labour productivity were doubled with combined use of fungicide and P fertilizer