Plant DNA flow cytometry and estimation of nuclear genome size.

Nuclear DNA Amounts in Angiosperms and their Modern Uses—807 New Estimates

Cereals are grown in almost every region of the world and are exposed to a variety of environmental stresses that severely affect their growth and grain yield. Of various abiotic stresses, salinity is one of the more significant threats to cereal crops. To ensure food security, there is a need to adopt strategies to overcome this specific threat. Undoubtedly, plant scientists have been exploiting a variety of approaches to achieve enhanced crop productivity on salt affected soils. Of the various biotic approaches, conventional breeding, marker-assisted selection and genetic engineering to develop salt-tolerant lines/cultivars of cereals all seem plausible. Some success stories have been reported for improvement in salt tolerance of wheat and rice, but are scarce for other cereals. A number of barriers to the development of salt-tolerant cultivars/lines have been identified and include a lack of knowledge about the genetics of crops, their physiological and biochemical behavior, wide variation in environme...

Improving Salinity Tolerance in Cereals

Quantitative trait loci (QTLs) controlling the morphological differences between pearl millet (Pennisetum glaucum ssp. glaucum) and its wild ancestor (Pennisetum glaucum ssp. monodii, form mollissimum) were investigated in a cultivated/wild F2 population by means of RFLP markers. The most critical adaptive changes resulting from the domestication process involved the spikelet structure: non-shedding seeds with reduced bracts and bristles and long involucral pedicel. Major differences also concerned characters describing the plant architecture, phenology and spike sizes. Many morphological differences could be attributed to the effect of a small number of loci with relatively large effects. These loci are mainly concentrated on four linkage groups (2, 5, 6 and 7). The loss of shedding ability, due to the absence of a functional abscission layer, is controlled by a single locus on linkage group 6 (al6). Genetic control of the other spikelet traits involved factors with large effects which are located in the region of linkage group 6 close to al6 and to an esterase gene, Esterase-E. Moreover, QTLs with large effects on plant and spike morphology traits such as plant height, number of spikes and weight of the spike were also mapped on linkage groups 6 and 7. This strong linkage of factors in the domestication syndrome may be involved in the maintenance of the phenotypic identity of wild and cultivated populations in sympatry. This result also brings new arguments in the understanding of the domestication process of this allogamous crop.

Genetic control of domestication traits in pearl millet (Pennisetum glaucum L., Poaceae).

Genome Size Variation in Central European Species of Cirsium (Compositae) and their Natural Hybrids

A systematic analysis of Pennisetum species has shown their cytological variability for basic chromosome number (x = 5, 7, 8, and 9), ploidy level, and chromosome size. We have identified the genome size and base composition of 15 species using flow cytometric procedure in order to test the relationship of these characters with the variation in basic chromosome number and to evaluate the ascendant dysploidy hypothesis from an ancestral x = 5 group. Ethidium bromide, bisbenzimlde Hoechst 33342, and chromomycln dyes have been used for genome size, percentage of AT, and percentage of GC nucleotides determination, respectively. Results show that genome sizes are variable among the Pennisetum species. This variation appears to be negatively related to the basic chromosome number. On the contrary, genome size Is not correlated with percentage of GC. This result shows that loss or gain of DNA that has occurred during evolution within this genus seems not to be especially associated with GCor AT-rich sequences.

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S. Siljak-Yakoviev

Papers

Genome Size Variation and Basic Chromosome Number in Pearl Millet and Fourteen Related Pennisetum Species