Esterase, total protein and seed storage protein diversity in Okra (Abelmoschus esculentus L. Moench)

Twenty-two accessions of okra (Abelmoschus esculentus), maintained at the Plant Genetic Resources Centre, Bunso, Ghana, were assayed for diversity in esterases, and total and storage proteins. A total of 34 reproducible and easily scorable bands were exposed with the number of bands per accession ranging from one to 21. All but nine of the bands were polymorphic. Storage proteins were the most diverse while esterases revealed the least diversity. Similarity matrices were calculated using the Jaccard coefficient, and input into cluster analysis. The phenogram produced by the UPGMA of the Jaccard similarity matrix from the pooled data of the esterases, and total and storage proteins revealed three major clusters at the 55% level of similarity. Accession 5 collected from Nyinguto was relatively distant from the other main clusters and separated at the 42% level of similarity. The second and third clusters comprised 11 and 10 accessions, respectively. It was observed that 18 out of the 22 accessions were distinct accessions. Similarity indices ranged from 29% to 100%. The wide range of similarity indices, coupled with the clustering of accessions, suggests useful variability in the collection for genetic conservationists and plant breeders

Molecular markers associated with a new source of resistance to the cassava mosaic disease

The predominant source of resistance to the cassava mosaic disease (CMD) is known to be polygenic requiring evaluation in multiple environments to characterise resistant genotypes, which makes the detection of genes for resistance using segregation analysis inefficient. Recently, some landraces have been identified which exhibit high levels of resistance to CMD. In this study, molecular markers associated with resistance to CMD in a resistant landrace were identified, using F1 progenies derived from a cross between the CMD resistant landrace TME7 and the susceptible line TMS30555, as a first step in marker assisted breeding for CMD resistance. Bulk segregant analysis (BSA) on the parents, resistant and susceptible DNA pools, using simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers revealed that an SSR marker, SSRY28-180, donated by the resistant parent was linked with resistance to CMD. Marker-trait association detected by regression analysis showed that the marker, accounted for 57.41% of total phenotypic variation for resistance. The analysis furthershowed that another SSR marker, SSRY106-207 and an AFLP marker, E-ACC/M-CTC-225, accounted for 35.59% and 22.5% of the total phenotypic variation for resistance, respectively. The implication of the results in breeding for resistance to CMD is discussed

Diversity analysis of sweet potato (Ipomoea batatas [L.] Lam) germplasm from Burkina Faso using morphological and simple sequence repeats markers

Collecting and characterizing plant material has been basic for crop  improvement, and diversity has long been seen as vital for rational management and use of crops. Thirty (30) morphological characters and thirty (30) simple sequence repeat (SSR) markers were used to assess the diversity among 112 sweet potato (Ipomoea batatas [L.] Lam) cultivars in Burkina Faso and to develop a core collection. Eight morphological  characters were able to differentiate the 112 accessions and to identify 11duplicates while 28 SSR markers were more informative in discriminating the accessions and to identify five duplicates. The diversity assessment using the two approaches revealed high diversity with a coefficient of 0.73 using the phenotypic data, while moderate diversity with a coefficient of 0.49 was obtained using the SSR markers. These results show no correlation between the two approaches (with dissimilarity index of 0.95). A core collection was constituted using the SSR based data while the eightdiscriminative phenotypic descriptors will be used in the identification of cultivars. Key words: Accessions, genetic diversity, germplasm, molecular markers, morphological characters, simple sequence repeat, sweet potato

Breeding for stress tolerance: Drought as a case study

Drought is an important climatic phenomenon which after soil infertility ranks as the second most severe limitation in the production of crops under rainfed, low input agriculture. Breeding of genotypes with greater drought tolerance is the best strategy for maintaining and/or increasing crop production in such systems. This paper reviews the concept of drought tolerance and discusses approaches that may be adapted to breed varieties of crops with tolerance to drought. What remains to be done is for breeders to use the available genetic variability with respect to mechanisms that aid the plant in adapting to drought in their breeding programmes. It is concluded that biotechnologies will prove quick and stable markers for identifying genes that confer drought resistance. Ghana Jnl agric Sci. Vol.32(2) 1999: 229-23

Effect of time of harvest, stage of fruit ripening, and post-harvest ripening on seed yield and germinability of local garden egg (Solanum gilo Radii)

Two cultivars of garden egg (Solanum gilo), Legon 1 and Nyaduahene, were used in the study. The first harvest was done 4 weeks after 50 per cent fruit set, followed by a second harvest, 4 weeks later. Seeds from three fruit maturity stages, mature white, yellow ripe and red ripe, were investigated. Seeds were extracted from half of the fruits harvested from each stage immediately after harvest while the other halves were stored at room temperature to ripen to the soft-red stage before seed extraction. Fruit weight in both cultivars decreased with plant age. Fruits harvested at the yellow-ripe stage produced the highest number of seeds per fruit. Fruits harvested at the mature white stage had the lowest seed yield. Seed yield was higher in the second harvest than in the first. Cultivar differences were observed in 1000-seed weight, but seed weight in both cultivars increased with fruit maturity. Post-harvest ripening to the soft-red stage increased the number of seeds extracted in fruits harvested at the mature-white stage as well as the 1000-seed weight in fruits harvested at the mature-white or yellow stages. Post-harvest ripening also improved the total percentage germination of seeds extracted from fruits harvested at the white or yellow stages, but decreased the percentage germination in seeds from fruits harvested at the red-ripe stage. Ghana Jnl agric Sci. Vol.32(2) 1999: 159-16

Influence of sett size and spacing on yield and multiplication ratio of ginger (Zingiber officinale Rosc.)

Four sett sizes (1, 2, 5, and 10 g) of ginger (Zingiber officinale Rosc.) and three spacings 12 cm W12 cm, 15 cm W 15 cm, and 15 cm W 23 cm) were studied for their effect on sprouting, vegetative growth, yield, and multiplication ratio. Percent sprouting in moist sawdust under greenhouse conditions was highest for the 10 g sett class and decreased with reduction in sett size. The largest and the smallest sett sizes had 100 and 75 per cent sprouting, respectively. There was a direct relationship between sett size planted and both vegetative growth and rhizome yield. The contrary was observed in sett size to rhizome ratio (multiplication ratio). The smallest sett size yielded a multiplication ratio of 9.85 compared to 4.78 for the largest sett size. Of the three spacing regimens investigated, the wider spacings produced higher vegetative growth as well as rhizome yield per plant. However, rhizome yield/ha was adversely affected by wider spacing. The highest yield of 29.69 t/ha was produced from the largest sett size (10 g) planted at the closest spacing of 12 cm W 12 cm. The combination of smallest sett size and widest spacing produced the lowest rhizome yield of 3.37 t/ha. Ghana Jnl agric. Sci. Vol.31(2) 1998: 175-18

Morphological and agronomic characterization of some tomato (Lycopersicon esculentum) germplasm in Ghana

In a study of morphological and agronomic characteristics of eight tomato accessions, a high variability was detected in plant height at flowering, fruit set, number of fruits per plant, fruit weight, number of locules per fruit, and yield. The variation in percent total soluble solids (3.9-5.0) and pH (3.9-4.4) was very small. The pH of the fruits in most of the accessions was close to 4.0 which is suitable for canning; however, the total soluble solids was below the 8 per cent required for canning. All of the accessions were highly sensitive to the high temperatures (28.6-32.2 oC) which prevailed during the period, resulting in low percentage fruit set (21.9-63.7). The overall correlations between number of fruits per plant, number of fruits per truss, fruit weight and yield were positive but very low (0.12-0.26). Some individual accessions, however, showed very high positive correlations between number of fruits per plant and yield (0.76-0.86) and number of fruits per truss and yield (r=0.63-0.89). The cultivar Wosowoso had a high negative correlation (-0.67) between number of fruits per truss and yield. Ghana Jnl agric Sci. Vol.32(2) 1999: 169-17

Genetic structure at the isocitrate dehydrogenase and malate dehydrogenase enzyme gene loci in cowpea (Vigna unguiculata (L) Walp) accessions

No Abstract Available Ghana Jnl agric. Sci, Vol.36 2003: 53-6

Molecular marker analysis of F1 progenies and their parents for carotenoids inheritance in African cassava (Manihot esculenta Crantz)

Cassava genotypes were assessed at genomic DNA level to estimate the genetic diversity within and between them using 36 simple sequence repeat markers (SSR). One hundred and forty-seven (147) F1 progenies derived from crosses amongst the parental genotypes were used to determine the association between three SSR markers and beta-carotene content in cassava. For the diversity study, a total of 131 alleles with an average of 3.7 alleles per locus were found. One yellow fleshed root genotype clustered with a white fleshed root genotype indicating similarity in their genetic background. Three SSR markers were used to screen the parental genotypes and their 147 progenies for a beta-carotene gene. The yellow fleshed root parents and 141 of the F1 progenies had SSR alleles associated with the presence of beta-carotene gene. The SSR markers identified for beta carotene at CIAT appeared linked to the trait as found in the parents, but evaluation in the progenies indicated that each marker did not account for high phenotypic variance individually. Marker NS 717 (allele 206) accounted for 20% beta carotene content and SSRY 301 (allele 331) accounted for 17%. There are minor QTLs that could probably be involved in beta carotene expression. The markers evaluated therefore do not sufficiently account for beta-carotene expression in the F1 progenies.Keywords: Cassava, simple sequence repeat (SSR), pro-vitamin A, diversity, validation. African Journal of Biotechnology, Vol 13(40) 3999-400