Screening <i>Colletotrichum gloeosporioides</i> f.sp <i>Manihotis</i> isolates for virulence on cassava in Akwa Ibom state of Nigeria.

Abstract

Six isolates of Colletotrichum gloeosporioides f.sp. manihotis obtained from anthracnose-infected cassava stems in six different cassava-growing locations of Akwa Ibom State were examined in the laboratory for morphological and physiological differences. The isolates were then screened in the greenhouse for virulence on cassava variety NR 8083 widely grown in Akwa Ibom State. Six-week old cassava plants were inoculated with 1ml of the spore suspension of each isolate of the pathogen at a concentration of 10 4 conidia/ml using a sterile hypodermal needle. One injection of inoculum was made at five different internodes of each cassava stem at an ambient temperature of 30 0 C and relative humidity of 80%. Results of laboratory examinations showed that mycelial growth on potato dextrose agar (PDA) medium was fastest (10.65mm/day) in isolate CGM 2 from Ikono and slowest (7.29mm/day) in isolate CGM 6 from Uyo. Sporulation of the isolates on PDA medium under alternate light and dark regimes was highest (9.30 x 10 6 spores/ml) in isolate CGM 4 from Nsit Atai and lowest (1.23 x 10 6 spores/ml) in isolate CGM 5 from Oruk Anam. Percentage spore germination and conidia length were highest (85.64% and 23.55µm) respectively in isolates CGM 4 from Nsit Atai and CGM 1 from Essien Udim and lowest (49.86% and 13.75µm) in isolate CGM 3 from Itu and isolate CGM 2 from Ikono, respectively. Results of greenhouse inoculations showed variations in lesion size for the different isolates. The largest (15.30mm) lesion was produced by isolate CGM 4 from Nsit Atai, followed by isolate CGM 1 (12.60mm) from Essien Udim. There were no significant (p> 0.05) differences in lesion size for isolates CGM 3 (8.63mm) from Itu, CGM 2 (8.45mm) from Ikono and CGM 6 (8.41mm) from Uyo. Lesion size was smallest (5.00mm) in isolate CGM 5 from Oruk Anam. Isolate CGM 4 of C. gloeosporioides f.sp manihotis from Nsit Atai which showed the highest sporulation density and percentage spore germination, one of the longest conidia and largest lesion size on inoculated cassava stems, appeared to be the most virulent of the six isolates of the pathogen in Akwa Ibom State during this investigation.

Morphological and molecular identification of Colletotrichum species associated with cassava anthracnose in Thailand

“…It has been assumed that C. gloeosporioides f.sp. manihotis and C. graminicola are the causes of CAD worldwide (Farr, Aime, Rossman, & Palm, ; Prihastuti, Cai, Chen, McKenzie, & Hyde, ; Wokocha et al., ). In Thailand, only C. gloeosporioides f.sp.…”

“…manihotis and C. graminicola have been reported as causal agents of cassava anthracnose disease (CAD). The disease has been observed in several countries including Tanzania , Nigeria , India, Indonesia and Thailand (Magdalena, Ernest, & Robert, ; Owolade, Dixon, Adeoti, & Osunlaja, ; Ratanacherdchai et al., ; Wokocha, Nneke, & Umechurba, ). In Nigeria, widespread incidence of the disease has been found to affect more than 80% of cassava grown in Ibadan in the Oyo state, and the disease was reported to have so reduced the number of healthy plantable stems available to farmers that a search for resistant cassava varieties was initiated in response to the crisis.…”

“…Severe anthracnose infection could result in loss of planting materials and reductions of total crop yield. Differences in susceptibility of cassava varieties to CAD also influence damage (Wokocha et al., ). Considerable stem damage due to the disease has also been reported in the Democratic Republic of Congo (DRC), where 90% of local cassava cultivars were rated as severely damaged (Lozano, Bellotti, Reyes, & Howland, ; Wokocha et al., ).…”

“…Differences in susceptibility of cassava varieties to CAD also influence damage (Wokocha et al., ). Considerable stem damage due to the disease has also been reported in the Democratic Republic of Congo (DRC), where 90% of local cassava cultivars were rated as severely damaged (Lozano, Bellotti, Reyes, & Howland, ; Wokocha et al., ). In Thailand, the occurrence of CAD was found to concentrate mainly in the northeast, resulting in marketable yield loss of up to 80%.…”

NUTRITIONAL AND PHYTOCHEMICAL STUDIES OF Jatropha tanjorensis Ellis & Saroja UNDER VARIED SOIL CONDITIONS.

“…Understanding how declining soil fertility influence the growth, and production of mineral nutrients and secondary metabolites have attracted considerable attention to evaluate the influence of soil status on the mineral nutrients and phytochemical contents of the test plants. 0 C, respectively [18,19]. Yenagoa is located at coordinates of 4° 55' 33.51"N and 6° 15' 33.58"E. Bayelsa State lies in the heaviest rainfall area of Nigeria with a mean minimum monthly temperature ranging from 25 o C to 31 o C [20 ].…”