Inoculum Concentration of Armillaria mellea in the Rhizosphere of Intercropped Teak Plantation: the case of the Opro Forest Reserve, Ghana

Teak (Tectona grandis Linn. F.) is the most planted timber tree species in Ghana, with over 73,916 hectares of plantation established at the end of 2008. Many of the teak plantations established in the semi-deciduous forest zones were done using the taungya system with various intercrops. Symptoms of Armillaria (Vahl: Fr.) root-rot of teak have been reported in the taungya plantations, especially in the semi-deciduous forest zones. The study aimed to determine inoculum concentrations of Armillaria mellea in the rhizosphere soil of intercropped teak and compare with sole teak plantation. Mycoflora were isolated from rhizosphere soil of teak intercropped with pepper, okra, maize, yam or cassava at year one to year three sapling stage. Dilution plate technique was used for mycoflora isolation and dilution factor of 10-3 was inoculated on potato dextrose agar amended with chloramphenicol (25mg/l) and incubated at 280C for 14 days after which A. mellea colonies were identified and counted. More A. mellea (Vahl: Fr.) colonies were isolated from rhizosphere soils of intercropped teak plantations than non-intercropped. Differences in A. mellea colonies were more significant amongst intercrops than amongst age of teak plantation at (P ≤ 0.05). There were significantly (P ≤ 0.05) higher numbers of A. mellea colonies in rhizosphere soils of teak intercropped with cassava compared with other intercrops. Number of A. mellea colonies in rhizosphere soils of intercropped teak did not have linear relation with age of teak plantation. Intercropping could promote Armillaria root rot of teak especially with cassava as intercrop

Search for Scutellonema bradys resistance in yams (Dioscorea spp.)

A study to examine variability in susceptibility of yams to Scutellonema bradys and to identify possible sources of resistance in Ghanaian yam germplasm (Dioscorea spp.) for use in yam improvement programmes, particularly, in West Africa was undertaken. Pot and field screening methodologies were used. In general, S. bradys and dry rot of tuber symptoms as well as tuber cracking increased during the storage period. The study showed a positive correlation between visual nematode damage and population densities in yam tubers. There was also a linear relationship between dry rot disease and tuber cracking at harvest and during storage. This confirms that S. bradys causes dry rot of tubers resulting in external cracking of yam tubers. Positive linear relationship was also observed between yam tuber weight loss and dry rot disease indicating that dry rot disease may have contributed to the tuber weight loss. Therefore, tuber dry rot symptoms caused by S. bradys of yams could be used to discard susceptible yams at harvest and after a period of storage. However, there was no linear relationship between nematode population densities in yam tubers and roots, therefore, a root protocol cannot be used for assessing resistance in yams as it could lead to misclassification. The yam germplasm screened, reaffirmed resistance to S. bradys in Dioscorea dumetorum var. Nkanfo and D. cayenensis var. Afun

CAPS markers TAO1 and TG105 in the identification of I2 resistant gene in Nigerian accessions of tomato, Solanum lycopersicum L.

Fusarium oxysporum (f.sp). lycopersici (Fol) is a soil-borne fungus that inhabits most tomato-growing regions of the world, causing vascular wilt disease. In Nigeria, the disease constitutes close to 40% loss in tomato yield annually. Cleaved Amplified Polymorphic Sequence (CAPS) markers TAO1 and TG105, developed elsewhere, were used to identify tomato accessions possessing the gene (I2) which confers resistance to Fol race 2. In this work, fifty Nigerian accessions of tomato, Solanum lycopersicum L., were screened with the two CAPS markers for resistant I2 gene. The primer pairs for TAO1 and TG105 produced amplification at 902 bp in 33 accessions and 450 bp in 38 accessions, respectively. The restriction enzymes Fok1 and Hinf1, for TAO1 and TG105 respectively, produced fragments at base pairs indicative of susceptible, homozygous and heterozygous resistant accessions to Fol. Restriction fragments from the two markers indicated that 11 accessions were homozygous resistant to Fol. Four of these accessions (Delila, Gem Pride, K-Small and Oxheart) occurred in the two molecular markers as homozygous resistant to Fol. The combined effect of the two markers enhanced precision in the identification of tomato accessions with resistance status to Fusarium vascular wilt.Keywords: CAPS markers, Fusarium wilt, I2 gene, tomato accession