Epidemiology and management of chickpea chlorotic dwarf virus (CPCDV) in chickpea (Cicer arietinum) in River Nile State-Sudan

In this study, surveys of chickpea fields for viruses in the River Nile State, and eight glasshouse and field trials were carried out in order to determine the importance of chickpea chlorotic dwarf virus (CpCDV), and to investigate the ecology and epidemiology of the virus.hmb Results of the surveys of chickpea fields for virus diseases revealed that stunt disease is the predominant disease that was encountered in the all fields visited. The incidence of stunt was found to range between 3.5-30 during 2001-2005 growing seasons, in different areas in River Nile State, whereas in Gezira Scheme, new area for chickpea production, the incidence was found to range between 10-20 in some selected areas, during 2005/2006 growing season. Serological tests using tissue blot immunoassay (TB IA) showed that CpCDV is the main virus associated with stunt disease. The ecological relationship between CpCDV and its leafhopper vector Orosius Orientals indicated that, transmission efficiency was increasing with the increase in the number of the insect vector. The use of 1, 3, 5, 10, and 15 gave rate of transmission of 30, 70, 88, 100, and 1000/0. The minimum period of time required by O. Orientals to acquire the virus from and inoculates into chickpea plants was less than 5 minutes. The latent period of CpCDV within the vector before it could transmitted it was found to be about three hours. The vector was also found to be capable to maintain CpCDV for 17 days up to its death. The spatial patterns of distribution of infected plants within chickpea fields as determined by ordinary runs analysis were random with exception of very few cases. The secondary spread of CpCDV was unlikely to take place. The temporal spread of CpCDV was rapid in the highly susceptible cultivar, ICCV -2, when planted in off season in the period from April to November, whereas the crop planted during winter showed low levels of stunt incidence and slow disease progress. For the determination of host range and sources of CpCDV infection only two weed species among many were found act as reservoirs and sources of CpCDV and these were; Hibiscus ficulneus and Datura stramonium. Other species showed positive reaction to CpCDV but their role as sources of infection was doubtful. Yield losses due to early infection of CpCDV were estimated as more than 90%. The effect of cultivar and sowing date on the incidence of stunt disease showed significant variations in stunt incidence, 23.2, 20, 27, and 70% in ICCV -2 planted in late October and early November, while in Shendi the average incidence was 6.2, 7, 3.6, and 10% in 2001-2005 respectively. On the other hand, late planting during the third week of November and early December, gave an average incidence levels of 2.5, 1.7, 1.2 and 5.1 % during the four seasons, respectively. Irrigation intervals of 7, 14, 21, and 28 days gave an average incidence of .9,15.2,15.6, and 28.1%, respectively in season 2001-2002, and 7,12.5, 17, and 19.3 in 2002-2003. The average incidence was also higher under an interval of 28 days (32.2 and 48.9%) than less than 7 days (5.3 and 10.9%) for 2003-2004 and 2004-2005, respectively. Regardless of irrigation intervals, the average incidence of stunt on ICCV -2 was 32.6% and 6.8% on Shendi as an average over the four seasons. None of the 232 chickpea genotypes screened was found resistant to CpCDV