Volume 6 Number 1 2012

CONTENTS AND ABSTRACTS

Samuel Adelabu, Onisimo Mutanga, Moses Azong Cho (South Africa) A Review of Remote Sensing of Insect Defoliation and its Implications for the Detection and Mapping of Imbrasia belina Defoliation of Mopane Woodland (pp 1-13)

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Review: Forest health, especially insect defoliation monitoring in forest using direct sampling and visual estimation has been only moderately successful due to its cost, time required for sampling, and most importantly the need to collect data immediately before and after an extreme event. However, remote sensing techniques offer timely, up-to-date, and relatively accurate information for sustainable and effective management of forest health. In this paper, we discuss the different approaches including the remote sensing platforms and techniques that have been used for assessing insect defoliation and its implications for detecting and monitoring mopane worm defoliationof mopane woodland, highlighting their strengths and weakness. Research gaps in the detection of insect defoliation with remote sensing are highlighted and future directions of research are also proposed.

Stanley Mukanganyama (Zimbabwe), Simbiso C. Dumbura, Leseilane Mampuru (South Africa) Anti-Proliferative Effects of Plant Extracts from Zimbabwean Medicinal Plants against Human Leukaemia Cell Lines (pp 14-20)

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Original Research Paper: A selected group of 14 medicinal plants was screened for antiproliferative activity against two human leukaemia cell lines Jurkat T and Wil 2 in vitro. The Trypan Blue assay was used to assess antiproliferative and cytotoxic activity. The five most potent medicinal plants showed the following order of potency against Wil 2 cell line: Parinari curatellifolia > Aloe barbadensis > Croton gratissimus > Syzigium guineense > Vernonia adoensis with IG₅₀sof 93, 115, 148, 149.8 and 130 µg/ml, respectively. The plants had comparable proliferation inhibition to the cancer drug doxorubicin. From these species, high levels of cytotoxicity were detected in extracts from Parinari curatellifolia and Aloe barbadensis to Wil 2 cell line at concentrations of 500 and 1 000 µg/ml. Croton gratissimus, Syzigium guineense and Vernonia adoensis extracts were found to be antiproliferative and not cytotoxic at the same concentrations. P. curatellifolia extract at a concentration of 10 µg/ml reduced cell proliferation of Jurkat T cells by 70% after 48 h of incubation. Studies were also carried out where the extract from P. curatellifolia combined with doxorubicin at concentrations 10 to 0.50 µg/ml were tested for antiproliferative activity against a Jurkat T cell line. The top five plant extracts had IG₅₀s of less than 150 µg/ml. The results show that plants used traditionally for treatment of diseases such as tuberculosis, mycosis and diarrhea can be used to inhibit cell proliferation in leukaemia cell lines. The extract from P. curatellifolia could be a potential source of lead compounds that may be used as anticancer drugs. The plant extracts that showed cytotoxicity and inhibition of cell growth will be further characterized to identify the active fractions and compounds.

Sofiane Abdelhamid (Tunisia) Genetic Variation and Characterization of Swiss Chestnut Cultivars (Castanea sativa Mill.) Using RAPD and AFLP Markers (pp 21-25)

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Original Research Paper: In order to study the genetic variation and to provide specific markers for genetic characterisation and identification of Swiss chestnut cultivars, two sets of molecular markers were explored: Random Amplified Polymorphic DNAs (RAPDs) and Amplified Fragment Length Polymorphic DNAs (AFLPs). 98 RAPD and 222 AFLP polymorphic markers were amplified using 12 and 4 primer combinations, respectively. Clustering analysis performed with the two sets of markers to group cultivars according to their similarity coefficients separated the genotypes into clear groups with different grades of success. The genetic identification of cultivars was more correct by RAPD than by AFLP. AFLP generated the highest number of polymorphic bands and clustered fairly closely-related chestnut cultivars. These results allowed problems generated by synonyms and homonyms in different chestnut accessions to be resolved. Molecular marker results were comparable. The similarity matrices based on the two sets of data give a highly significant positive correlation between RAPD and AFLP (r = 0.78).

Michael I. Uguru (Nigeria), Benedict C. Oyiga (Germany), Elias A. Jandong (Nigeria) Responses of Some Soybean Genotypes to Different Soil pH Regimes in two Planting Seasons (pp 26-37)

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Original Research Paper: Seven genotypes of soybean (Glycine max (L.) Merrill) were screened in 2004 and 2005 planting seasons at the experimental research farm of the University of Nigeria, Nsukka to identify the acid tolerant genotypes using some agronomic and yield traits. These genotypes were screened under varying soil pH conditions. The results revealed that the genotypes varied considerably in the agronomic and yield traits at the different pH values. The soil pH, genotype and their interactions had significant effects on most of the traits evaluated in both planting seasons. The traits were greatly reduced at soil pH < 5.5 and, it increased progresively with increase in the soil pH up to 6.0. The principal component analysis (PCA) indicated that the first three principal components contributed 71.12 and 69.28% of the total variability among the genotypes in the 2004 and 2005 plantings, respectively. Thus, under soil acid conditions traits such as root length, fresh root weight and number of nodules are discriminating and can serve as selection criteria to distinguish between acid tolerant and acid-sensitive genotypes. In the 2004 planting, ‘Digil’, ‘Garikida’ and ‘Sunkani’ were identified as tolerant; ‘Kyado’ and ‘Sebore’ as moderately tolerant; ‘Gembu’ is moderately susceptible while ‘TGX1448-2E’ is suceptible to soil acidity. In 2005, ‘Sebore’ and ‘Digil’ were identified as acid-tolerant; ‘Gembu’ and ‘Sunkani’ as moderately tolerant; ‘Garikida’ and ‘TGX1448-2E’ as moderately susceptible and ‘Kyado’ as suceptible to low soil pH. The tolerant genotypes had normal root growth and higher seed yield at pH < 5.5 in both planting seasons indicating their tolerance to low soil pH. The results suggest that ‘Kyado’, ‘Sebore’ and ‘Digil’ can therefore be included in breeding programs to develop new genotypes that can withstand low soil pH conditions in the derived savanna region of south eastern Nigeria.

Ibrahim Y. Dugje, Adam L. Ngala, Haliru Yakubu (Nigeria) Effects of Cowpea Planting Date and Phosphorus Level on Striga Infestation, Growth and Yield of Cowpea Intercropped with Pearl Millet in a Nigerian Sudan Savanna (pp 38-43)

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Original Research Paper: Grain yield of cowpea (Vigna unguiculata (L.) Walp is usually reduced when intercropped with pearl millet (Pennisetum glaucum (L.) R. Br.)) in the low fertility soils in the Sudan savanna of Nigeria. Field experiments were conducted to determine the influence of cowpea planting date and phosphorus (P) levels on Striga gesenerioides infestation and grain yield of cowpea grown in mixture with pearl millet during 2005 and 2006 rainy seasons. Five cowpea planting dates: 0, 10, 20, 30 and 40 days after millet planting (DAMP) and three P levels: 0, 30 and 60 kg P₂O₅/ha, were evaluated in randomized complete block design in a factorial arrangement. Each treatment was replicated three times. The results showed that cowpea growth, yield and yield component parameters and Striga infestation of cowpea were significantly reduced with delay in planting cowpea. Increase in P levels significantly increased vegetative and yield parameters of cowpea and reduced Striga infestation. There were significant positive linear relationships among cowpea agronomic parameters (r = 0.25 to 0.96). Seed yield/ha was negatively correlated with Striga count (r = -0.51) and 100-seed weight (r = -0.38). The simultaneous planting of cowpea and pearl millet or planting cowpea within 10 days after pearl millet and each combined with 30-60 kg P₂O₅/ha improved cowpea grain yield and reduced Striga infestation in cowpea when intercropped with pearl millet in the Sudan savanna.

Ibrahim Y. Dugje, Adam L. Ngala (Nigeria) Influence of Cowpea Planting Date and Phosphorus Level on Striga Infestation and Performance of Pearl Millet in Mixture with Cowpea in a Nigerian Sudan Savanna (pp 44-49)

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Original Research Paper: Pearl millet is traditionally grown in mixture with cowpea in the savanna region of Nigeria. Field experiments were conducted to determine the response of pearl millet to varying dates of planting cowpea and phosphorus levels during the 2005 and 2006 rainy seasons. A randomized complete block design in factorial arrangement was used to evaluate five cowpea planting dates (0, 10, 20, 30 and 40 days after planting millet) and three phosphorus levels (0, 30 and 60 kg P₂O₅/ha), each replicated three times. The results showed that Striga counts and pearl millet plant height significantly increased with delayed in planting cowpea, while number of grains/panicle, seed weight and grain yield/ha significantly decreased with delay in planting date. Increase in P levels significantly reduced Striga counts, but had no significant effect on grain yield/ha. Grain yield/ha was inversely associated with Striga counts (r = -0.28 to -0.42), but positively correlated with number of grains/panicle (r = 0.52 to 0.89) and seed weight (r = 0.27 to 0.35). The competitive effects of cowpea on pearl millet were balanced by substantial gain in cowpea grain yield for simultaneous or planting cowpea within 10 days after pearl millet. Therefore, both pearl millet and cowpea should be planted simultaneously or within 10 days after planting pearl millet as each proved beneficial to pearl millet and enhanced the productivity of the system in the Nigerian savanna.

Oladayo O. Idowu-Agida, Dotun J. Ogunniyan, Emmanuel O. Ajayi (Nigeria) Screening Long Cayenne Pepper (Capsicum frutescens L.) Accessions Collected from Southwest Nigeria for Agronomic Performance (pp 50-55)

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Original Research Paper: Germplasm collections and selection for agronomic traits are essential for genetic enhancement. Capsicum has great genetic diversity; greater than 200 landraces are grown in Nigeria, but there are no recommended cultivars. An experiment was conducted at the National Horticultural Research Institute of Nigeria, Ibadan to evaluate and select long cayenne pepper accessions, collected from 31 locations in Southwest Nigeria, for agronomic performance in rainy and dry seasons of 2008. Six-week-old seedlings of the pepper accessions were transplanted using 0.6 × 0.6 m spacing (28 plants/plot) into 3.6 × 2.4 m beds, separated by 1 m. Data were collected on eight middle plants on growth, flowering and fruit traits in both seasons. Data collected were subjected to analysis of variance; least significant difference was used to separate means, and least means square used to explain results of interactions. Different accessions were adapted to each season. Season had no effect on seedling vigour, plant height, number of seed/fruit and 1000-seed weight; butdryness hastened flowering and fruiting. Fruit yield/plant and number of seed/fruit were higher in the dry than rainy season. Accessions IA108-9, IA108-10, IA108-12, IA108-13, IA108-14, IA108-20 and IA108-28 performed best under rain-fed; accessions IA108-2, IA108-5, IA108-8, IA108-19, IA108-23 and IA108-31 did best in the dry season; and accessions IA108-3, IA108-4, IA108-7 and IA108-29 performed well in both seasons. Fruit yield/plant in ‘IA108-28’ (>100 g) was stable across seasons; the accession could be selected for further studies in Ibadan.

Oyebamiji O. Oyegoke, Samuel A. Babarinde, Akinola J. Akintola, Zainab B. Olatunji (Nigeria) Bioactivity of Ocimum sanctum Linn. Leaf Powder and Extracts against Tribolium castaneum Herbst (pp 56-59)

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Original Research Paper: Two formulations of Ocimum sanctum L. (powder and extract) were used to test for its toxic and repellent properties against Tribolium castaneum in the laboratory. A toxicity test consisted of exposing T. castaneum larvae to millet (Pennisetum glaucum (L.) R. Br.) seeds treated with three dosages (0, 0.15 and 0.3 ml/5 g seeds) and millet flour admixed with three dosages (0, 0.25 and 0.5 g/5 g flour). In the case of the leaf powder, mortality increased with increase in concentration, with highest percentage mortality (63.5%) observed with 0.5 g O. sanctum. However, when two extracting solvents were used for extraction, acetone evoked greater mortality than petroleum spirit. Although petroleum spirit had greater repellent effects, it was not dependent on dose. Percentage repellency followed a progressive increase when acetone was used for extraction with the significantly (P < 0.05) highest percentage repellency (86%) observed with 0.3 ml/30 cm².

Sherin Mahfouze, Eman Khattab (Egypt), Nour Gadalla (Egypt/Kingdom of Saudi Arabia) Resistance of Faba Bean Accessions to Bean Yellow Mosaic Virus and Broad Bean Stain Virus (pp 60-65)

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Original Research Paper: The primary objective of this study was to find new faba bean (Vicia faba) accessions resistant of Bean yellow mosaic virus (BYMV) and Broad bean stain virus (BBSV). In addition, since little genetic information is available on the resistance of faba beanto these viruses, this study aimed to investigate the changes in peroxidase activity and protein composition in faba bean leaves resistant to both BYMV and BBSV. The 15 faba bean accessions had different resistance to BYMV and BBSV based on disease index. Accessions No. 3, 4, 8 and 12 were immune while accessions No. 1, 5, 7, 9, 10, 11, 13 and 14 were highly resistant; accessions No. 6 and 15 were moderately resistant and accession No. 2 was tolerant. SDS-PAGE and POD-isozymes patterns were used to studying genetic variability among the immune, tolerant, or susceptible 15 faba bean accessions under mixed infection with both BYMV and BBSV. 12 protein markers with molecular sizes ranging from 145.2 to 6 KDa were observed in immune, tolerant and resistant plants but which were not present in the control. The highest number of markers appeared in accession No. 3 (six markers). Most pathogen-related proteins were observed in diseased plants with both BYMV and BBSV, e.g., accession No. 14 in which four bands appeared (92, 86.5, 21 and 14.8 KDa). Peroxidase activity increased in all faba bean accessions except for accessions No. 2, 11 and 15. Increasing peroxidase activity was related with host resistance to both viruses.

Olagorite Adetula, Gbenga Akinwumi (Nigeria) Assessment of Varietal Growth of Plantain and Banana in South-western Nigeria (pp 66-69)

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Original Research Paper: Southwestern parts of Nigeria are located within savanna and forest agro-ecological zones in which the economy is agrarian in nature. The major crops intercropped with plantain and banana are cocoa (when young) and cocoyam. This research was therefore geared toward the collection of various types of plantains and bananas commonly grown in the south west in order to increase genetic lines in the gene bank of the National Horticultural Research Institute, Ibadan. Information was obtained from six states (Lagos, Ogun, Osun, Ondo, Ekiti and Edo). Data were collected from farmers in 50 farms from each state who had large and small farms using direct questioning, measuring tapes for plant height, stem girth, leaves length and breadth. Soil observations on each farm were carried out and soil characteristics such as texture, stoniness and colour were determined. The results of the survey indicate that farmers had given more attention to the cultivation of the crops either intercropped with cocoyam or cocoa (when young) or when planted as a sole crop. The majority of farmers had their plantain and banana farms in their backyards. Most of their cultural practices were rain-fed with uniform population variability. ‘Saro’ banana variety showed significant difference (P < 0.05) among the mean value in plant height and stem girth with Owode Owena banana recorded highest plant height and stem girth when compared with Owan and Aramoko. The major constraints to production were nematodes, weevil infestation and the lack of knowledge of cultural and maintenance practices.

Jetro Nkengafac Njukeng, Eugene Ejolle Ehabe, George Elambo Nkeng (Cameroon) Estimating Organic Carbon from Loss-on-Ignition and pH in Some Cameroon Hevea brasiliensis Plantation Soils (pp 70-72)

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Short Communication: Recent studies on carbon sequestration and climate change require accurate estimates of soil organic carbon (SOC) following its importance in carbon storage studies. This study evaluates the use of loss-on-ignition (LOI) as a rapid, less costly and accurate method for estimating SOC considering the errors associated with estimation of the latter. LOI-SOC-pH regression equations were obtained using data from analyses of topsoils (0-15 cm deep) in mature rubber plantations in the humid forests of south west Cameroon. Indeed, significant linear equations characterized SOC-LOI and SOC-pH (KCl) relations. The rather weak LOI-SOC relations (r² ≤ 0.38) would indicate that this parameter may serve as an accurate estimate for SOC upon its modification following a mastery of factors responsible for its variability.

Abioye Olabode, Olagorite Adetula, Gbenga Akinwumi (Nigeria) Prospects and Constraints of Marketing Musa spp. in Southwest Nigeria (pp 73-75)

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Research Note: The bulk of Musa spp. output come from large numbers of very small scattered farms making the task of collection and distribution more complicated. A survey was undertaken to study the prospects and constraints of marketing of banana and plantain in south west Nigeria, during the period of January to May 2008. 150 marketers were selected in six states at random for the interview using structured questionnaires. Data were analyzed using descriptive statistics, marketing margin and t-test. The result of the analysis showed that 80% of respondents were female and 20% male. Majority of respondents had ten years experience. Above (68%) were middle aged people. Analysis also indicated that 40, 35 and 53% sourced their fund through contribution (Esusu), family and personal savings respectively. The majority of respondents (72%) had the problem of collection since farms are small and scattered with little access. According to respondents the average purchasing price of big and small bunch of plantain were Ν251 and Ν95.60 respectively while, big and small banana bunch were found to be Ν104.60 and Ν62.80 respectively. Also average selling price of big and small bunch of plantain were Ν573 and Ν188.60 respectively. While big and small bunch of banana were sold for Ν250.80 and Ν125.00 respectively. The result of t-test analysis showed that the cost price was significant (P<0.05) different from the selling price of plantain and banana. This indicated that marketing of the crops is highly profitable. Finally, these surveys revealed high level of profitability associated with the marketing of plantain and banana, if government assists in the provision of credit facilities to the sellers and accessible roads to the producers.