Genetic diversity in 14 tomato (Lycopersicon esculentum Mill.) varieties in Nigerian markets by RAPD-PCR technique

A total of 226 tomato (Lycopersicon esculentum Mill.) fruits sold in markets within three states in Southwestern Nigeria were purchased and differentiated into 14 varietal groups based on morphological parameters. The genomic DNA from the young apical leaves of the seeded plants were extracted and analyzed by the randomly amplified polymorphic DNA-polymerase chain reaction (RAPDPCR) technique. Seventy-four (74) amplified products were scored with 62.2% of them revealing polymorphism. The OPB-18 primer recorded the highest polymorphism (83.3%) and OPU-14 the least (44.4%). The dendrogram revealed 3 clusters. The genotypic relationships between varieties within clusters ranged from 2 in clusters 1 and 3 to 10 in cluster 2. Cluster 2 revealed 4 subgroups with two pairs of varieties (var. c and i and l and m) showing 100% similarities. The local names, place of cultivation and phenotypic characters expressed by the varieties were not suitable for varietal differentiation since phenotypically different fruits showed genotypic relatedness. The impression that tomato varieties from a particular geographical zone are genetically similar was therefore nullified.Key words: Tomato, randomly amplified polymorphic DNA, polymerase chain reaction, molecular, genetic diversity, Lycopersicum

Variation in maize tolerance to Striga Lutea (Lour) and influence of Arbuscular Mycorrhizal Fungi

This study was conducted to assess the variation in maize tolerance to Striga lutea and influence of arbuscular mycorrhizal fungi (AMF). Screen house experiment was conducted at the Institute of Agricultural Research and Training, Ibadan while, Farm settlement and Temidire were striga endemic experimental fields in Eruwa. Complete randomized design was used in screen house while, randomized complete block design was adopted on the field with three replications. AMF (Glomus mosseae, G. clarum, G. deserticola and Gigaspora gigantea) in mixtures of soil and root fragments were inoculated at the rate of 25g per plant while, 10.4g of extracted striga seeds were artificially  infested. Uninoculated and uninfested in pots and plots served as control. Four maize genotypes; ILE1- OB, ART-98-SW4-OB, ART-98-SW5-OB and ART-98-SW6-OB were screened for tolerance or susceptibility to S. lutea infestation on disease rating scale of 1 to 9. ART-98-SW5-OB and ART-98-SW6-OB were significantly tolerant (P<0.05) with striga damage rating (SDR) ranging from 1.18-2.48, ART-98-SW4-OB was moderately tolerant with SDR ranging from 3.59-4.57, while ILE-OB was highly susceptible with SDR ranging from 8.61-8.72. Influence of AMF was significant (P<0.05) for growth, yield and striga-related traits with SDR ranging from 1.28- 2.70 and 1.21-2.64 at 8 and 10 weeks after planting respectively.Key words: Maize, mycorrhiza, Striga lutea, tolerance, yiel

Comparative Efficacy and Economic Viability of Trichoderma Strains as Bio-Control Agents for the Control of Phytophthora Pod Rot of Cocoa in Nigeria

The comparative efficacy and economic viability of Trichoderma species as bio-control agents against Phytophthora megakarya which has been hitherto elusive was determined by field application/evaluation, bean yield and accruable revenue evaluation. The trials followed randomized complete block design (RCBD) with 3 field constituting blocks, 24 treatments with 3 trees per treatment per replicate. The treatments were three fungicides, five bio-agents, fifteen combinations of fungicides and bio- agents while the control consists of unsprayed trees. Data were collected on total pod produced (TP), total number of disease pods (DP) and total number of fermentable pods per tree per treatment (FP) while revenue accrued (RA) and revenue-cost-ratio were also determined accordingly. All the bio-agents significantly reduced the percentage pod-rot on the field. The highest mean pod-rot incidence (16.91) among the treated was significantly lower than the control (30.14). This was observed on BA (NIG-T287) sprayed plots. Funguran 0H + NIG-T289 produced the highest (757) number of pods while the least pod production (312) was observed with Copper Sulphate + NIGT289 (F3BC) treated plots. The highest revenue-cost-ratio (69.45) was obtained from Copper Sulphate treated plots, while the least revenue-costratio (2.85) was obtained from Ridomil Gold + NIG-T288 treated plots. NIGT293 performed better than other bio-agents and most of other treatments when applied sole resulting to 45.90 comparative efficacy and economic viability. These bio-agents were successfully combined with fungicides thereby reducing the frequency of fungicide application from four to one with significant pod-rot reduction on the field, comparatively high yield and more profit (high revenue-cost-ratio).Keywords: Bio-control agents, comparative efficacy, economic viability,revenue-cost-ratio

Production of cell wall enzymes in pepper seedlings, inoculated with arbuscular mycorrhiza Glomus etunicatum

Pepper seedlings inoculated with arbuscular mycorrhizal AM fungus, Glomus etunicatum, produced cellulase, polygal-acturonase and pectin methylestrase enzymes. The activities of the enzymes increased as the pepper seedlings matured in age, showing that the activity of the enzymes in the seedlings was age mediated. The pectinases showed higher activity than the cellulase enzyme which may indicate establishment of the mycorrhizal in the host. The significance of this finding is that there is an initial infectivity factor in (AM) fungi interactions with plant just like in other host-parasite interaction. Tanzania Journal of Science Volume 27 (2001), pp. 1-

Antibacterial activities of constituents from Isolona cauliflora and Cleistochlamys kirkii

Antibacterial activities of caulindole D, a mixture of caulindole E and F, pinocembrin and an oxyheptanoid (cleistenolide), obtained from stem barks of Isolona cauliflora and Cleistochlamys kirkii, on Staphylococcus aureus and Pseudomonas phaseolicola were determined. An in vitro assay test by paper disc method showed that the caulindole D, E and F from Isolona cauliflora produced no inhibition zone on both bacteria pathogens at 100-200 ppm while cleistochlamic acid from C. kirkii showed weak to moderate inhibition zone at 100-200 ppm. At concentration above 200 ppm, the bacteria pathogens were inhibited by all the compounds isolated from the plant extracts. Furthermore, there was an influence of bioassay method on the sensitivity of extracts on both test bacteria. Tanz. J. Sci. Vol.29(2) 2003: 19-2

Genetic diversity of Colletotrichum gloeosporioides in Nigeria using amplified fragment length polymorphism (AFLP) markers

Colletotrichum gloeosporioides is the causal agent of yam anthracnose disease in Nigeria. Differential cultivars and amplified fragment length polymorphic DNA markers were used to assess the extent of genetic diversity among 39 isolates of the pathogen. Fourteen (14) pathotypes of the pathogen were identified based on inoculation of a differential set of Dioscorea alata genotypes of which pathotype P11 was the most virulent attacking all differential D. alata host genotypes, while pathotype P8 was the least virulent. 52% of the isolates were avirulent, 23% were slightly virulent and 25% were virulent. Amplified fragment length polymorphism (AFLP) analysis confirmed genetic variation among the C. gloeosporioides isolates and was effective in establishing genetic relationships between them. However, the grouping of the isolates based on AFLP analysis was not directly related to virulence groups or geographical origin of the isolates. The genetic variation in C. gloeosporioides is important in choosing strategies to develop durable resistanceKeywords: Anthracnose disease, pathotypes, genetic diversity, amplified fragment length polymorphism (AFLP) markers, ya