Natural variation in fruit characteristics,seed germination and seedling growth of <Emphasis Type="Italic">Adansonia digitata</Emphasis> L. in Benin

Adansonia digitata (baobab tree), a multipurpose tree species, occurs throughout semi-arid and arid zones of Africa. Its survival is, however, threatened by bush fire, over-exploitation, grazing and a lack of natural regeneration. The extent of variation in fruit characteristics, seed germination and seedling traits of the baobab tree in Benin, was evaluated at climatic zone level. 1,200 fruits were sampled in each of the three climatic zones of Benin for morphological assessment and to assess germination rate and seedling growth dynamics according to the climatic zones, the used substrate and the scarification of the seed coat. There were significant differences in fruit characteristics not only between climatic zones but also between individuals from the same zone and within-trees. Using mechanical scarification on freshly-collected baobab seeds negatively affected the germination rate of baobab seeds sampled in the Guinean and Sudano-Guinean zones of Benin. The best-germination rate was recorded for non-treated seeds from the Guinean zone, up to 57% on day 25. All seeds germinated best on the sand substrate, but supplying organic matter promoted further seedling growth after 11 days of germination. Based on these observations we propose some strategies for efficient ex situ conservation of baobab in Benin.     

Analysis of ITS of the rDNA to infer phylogenetic relationships among Vietnamese Citrus accessions

This study focused on clarifying phylogenetic relationships among Citrus accessions from Vietnam. Our phylogenetic analysis based on nucleotide sequences from the ITS of the ribosomal DNA included 69 accessions belonging to Citrus and related (sub)genera. Maximum parsimony and Bayesian analysis confirmed a clear separation of the three ‘true’ Citrus species (C. medica, C. maxima and C. reticulata). Confirming recent taxonomic revisions, Fortunella, Poncirus trifoliata and Citrus hystrix are clustered among the accessions of subgenus Citrus. C. × sinensis accessions revealed a close evolutionary relationship to either C. maxima or C. reticulata, thereby confirming their involvement in its hybrid origin. Also, some other hybrid taxa and their proposed parental species were investigated and their origin could in some cases be confirmed using the ITS sequence data.     

Maternal inheritance of cytoplasmic organelles in intergeneric hybrids of Carica papaya L. and Vasconcellea spp. (Caricaceae Dumort., Brassicales)

The mode of inheritance of chloroplast and mitochondrial DNA has been determined in intergeneric hybrids between C. papaya and four different Vasconcellea species by employing a restriction fragment length polymorphism analysis of a PCR-amplified chloroplast and mitochondrial DNA region. Artificial F₁ hybrids were produced between a female specimen of C. papaya and male specimens of either V. parviflora, V. goudotiana, V. cundinamarcensis or V. quercifolia. The hybridization patterns of all hybrids correspond in all cases with that of the C. papaya mother, and are different from that of the paternal Vasconcellea species, thus indicating the maternal inheritance of cpDNA and mtDNA in intergeneric hybrids between C. papaya and wild relatives of the Vasconcellea genus.     

Genetic fingerprinting using AFLP cannot distinguish traditionally classified baobab morphotypes

Baobab (Adansonia digitata L.) is one of the predominant tree species in West African agroforestry systems. A local morphological classification system is used by farmers, identifying trees with desired or undesired combinations of traits. This study evaluates the genetic significance of these morphotypes by comparing local identification with AFLP marker information. Eight morphotypes were recognized by seven ethnic groups from Benin, Ghana and Senegal, among 182 sampled baobab trees. Five primer pairs were used for DNA fingerprinting, resulting in a total of 254 scored bands, of which between 94.1% and 100% was polymorphic within morphotypes. Generally, genetic fingerprinting did not correlate with the traditional morphological identification of Adansonia digitata. Probably, AFLP markers are not directly linked to the differences in phenotype or the traits used for the traditional classification are largely dependent on environmental factors. Since no genetic differentiation is found between the morphotypes, a morphotype-based approach in the collection of genetic variation for conservation programs is not advisable. A. E. Assogbadjo and T. Kyndt equally contributed to this work.     

Sensitivity towards DMI fungicides and haplotypic diversity of their CYP51 target in the Mycosphaerella graminicola population of Flanders

Journal of Plant Diseases and Protection - Septoria leaf blotch, caused by the fungus Mycosphaerella graminicola, is the most important wheat disease in Northwestern Europe, and is currently...