Gametophytic competition in pearl millet, Pennisetum typhoides (Stapf et Hubb.)
TL;DR: Factors affecting reproductive strategies of pearl millet, which is currently classified as a predominantly allogamous species, were investigated and a better competitive ability of autopollen on various types of allopollen was systematically found for the Ligui genotype.
Abstract: Factors affecting reproductive strategies of pearl millet, which is currently classified as a predominantly allogamous species, were investigated. Gametophytic competition as well as the effect of growth temperature on this phenomenon were studied by means of the pollen mixture technique. The relative competitive ability of pollen from five different genetic stocks (Ligui, Massue, "Chinese," Thiotande, 23d2B) was assessed by isozyme electrophoresis (esterase, alcohol dehydrogenase) of progeny plants. Gametophytic competition with a polygenic inheritance trend for pollen competitive ability is reported. A better competitive ability of autopollen on various types of allopollen was systematically found for the Ligui genotype. Temperature stress enhanced this trend. Hypotheses on the role of gametophytic competition in the evolution of the primary genetic pool of P. typhoides are discussed.Key words: pearl millet, pollen, competitive ability, segregation distortions.
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TL;DR: Molecular evaluation of natural introgression linked to investigations of farmer recognition and use of introgressed types provide ways of evaluating whether farmer selection for introgressive types is a significant process in increasing the genetic diversity of crop plants.
Abstract: Whether new combinations of genes that result from hybridization and introgression between wild and cultivated taxa are maintained, with the resultant development of populations with new characteristics, depends on natural selection, and in the case of crops, on human selection. While many cases of deliberate introgression of desirable traits into crop cultivars as part of breeding programmes are known, the extent and significance of natural or farmer-assisted introgression is uncertain. A range of techniques have been used to document natural hybridization and introgression of agricultural crops and their wild relatives in many crops including maize, wheat, barley, oats, pearl millet, foxtail millet, quinoa, hops, hemp, potato, cocona, casava, common bean, cowpea, pigeon pea, carrots, squash, tomato, radish, letuce, chilli, beets, sunflower, cabbage, and rasberries. However, the majority of these studies are based on morphological characters, and few have investigated the frequency with which such new types are produced and retained in natural and agroecosystems for farmer selection. Even more limited is information on the role of farmers in recognizing and selecting new genetic variation from the natural introgression of crops with their wild relatives, and the impact, once selected, of these new genetic combinations on the crop diversity. Molecular evaluation of natural introgression linked to investigations of farmer recognition and use of introgressed types provide ways of evaluating whether farmer selection for introgressed types is a significant process in increasing the genetic diversity of crop plants.
219 citations
TL;DR: A significantly lower number of alleles and lower gene diversity in cultivated pearl millet accessions than in wild accessions is shown, which contrasts with a previous study using iso-enzyme markers showing similar genetic diversity between cultivated and wild pearl Millet populations.
Abstract: Genetic diversity of crop species in sub-Sahelian Africa is still poorly documented. Among such crops, pearl millet is one of the most important staple species. In Niger, pearl millet covers more than 65% of the total cultivated area. Analyzing pearl millet genetic diversity, its origin and its dynamics is important for in situ and ex situ germplasm conservation and to increase knowledge useful for breeding programs. We developed new genetic markers and a high-throughput technique for the genetic analysis of pearl millet. Using 25 microsatellite markers, we analyzed genetic diversity in 46 wild and 421 cultivated accessions of pearl millet in Niger. We showed a significantly lower number of alleles and lower gene diversity in cultivated pearl millet accessions than in wild accessions. This result contrasts with a previous study using iso-enzyme markers showing similar genetic diversity between cultivated and wild pearl millet populations. We found a strong differentiation between the cultivated and wild groups in Niger. Analyses of introgressions between cultivated and wild accessions showed modest but statistically supported evidence of introgressions. Wild accessions in the central region of Niger showed introgressions of cultivated alleles. Accessions of cultivated pearl millet showed introgressions of wild alleles in the western, central, and eastern parts of Niger.
139 citations
Cites background from "Gametophytic competition in pearl m..."
...Phenology (Renno and Winkel 1996), pollen competition (Sarr et al. 1988; Robert et al. 1991), and reproductive barriers (Amoukou and Marchais 1993) could explain this result....
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TL;DR: It is found that a monophyletic origin of cultivated pearl millet in West Africa is the most likely scenario supported by the data set and the phylogenetic relationship among accessions not showing introgression is analyzed.
Abstract: During the last 12,000 years, different cultures around the world have domesticated cereal crops. Several studies investigated the evolutionary history and domestication of cereals such as wheat in the Middle East, rice in Asia or maize in America. The domestication process in Africa has led to the emergence of important cereal crops like pearl millet in Sahelian Africa. In this study, we used 27 microsatellite loci to analyze 84 wild accessions and 355 cultivated accessions originating from the whole pearl millet distribution area in Africa and Asia. We found significantly higher diversity in the wild pearl millet group. The cultivated pearl millet sample possessed 81% of the alleles and 83% of the genetic diversity of the wild pearl millet sample. Using Bayesian approaches, we identified intermediate genotypes between the cultivated and wild groups. We then analyzed the phylogenetic relationship among accessions not showing introgression and found that a monophyletic origin of cultivated pearl millet in West Africa is the most likely scenario supported by our data set.
130 citations
Cites background from "Gametophytic competition in pearl m..."
...The frequency of this wild/cultivated hybridization is however variable and several factors limit or enhance gene flow locally, such as flowering phenology, pollen competition and reproductive barriers (Sarr et al. 1988; Robert et al. 1991; Amoukou and Marchais 1993; Renno and Winkel 1996)....
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Book•
10 Oct 2011
TL;DR: Methods in molecular genetics are now facilitating the isolation of genes responsible for controlling pollen development and pollen-stigma interactions, resulting in a revolution in understanding of these crucial events in plant reproduction.
Abstract: The biology of pollen development and the phenomenon of self-incompatibility has long been a subject of great interest to plant biologists. Methods in molecular genetics are now facilitating the isolation of genes responsible for controlling pollen development and pollen-stigma interactions, resulting in a revolution in our understanding of these crucial events in plant reproduction. The contributions in this volume present current research on the physiology, molecular genetics and biotechnology of pollen and ovule development and interactions in angiosperms.
90 citations
TL;DR: The identification and chromosomal localization of the genes that mainly affect pollen fitness variability were carried out by RFLP analysis, applied to a recombinant inbred population that had been characterized for about 200 restriction loci.
Abstract: Pollen competition and variability in pollen fitness can produce non-random fertilization with respect to pollen genotypes, and, owing to the large extent of genetic overlap between the gametophytic and sporophytic phases of the life-cycle, can affect the latter. Differences in pollen fitness are due to many factors, of which pollen grain germinability and pollen tube growth rate are the main components. The identification and chromosomal localization of the genes that mainly affect pollen fitness variability were carried out by RFLP analysis, applied to a recombinant inbred population that had been characterized for about 200 restriction loci. Germination ability and pollen tube growth rate were evaluated by means of the pollen mixture technique. Both traits revealed a large variability and high heritability (0.71±0.05 for tube growth rate and 0.77±0.04 for grain germinability). Analysis of the association between the expression of the characters and the allelic composition at each of the restriction loci revealed a significant regression on 29 loci in the case of pollen tube growth rate and on 26 in the case of pollen grain germinability. However, considering only uncorrelated loci, in order to avoid false assignments, the minimum number of quantitative trait loci (QTL)s with major effects was five for the tube growth rate and six for grain germinability. The amount of genetic variability of the characters explained by the molecular markers was 0.89 (tube growth rate) and 0.79 (grain germinability), signifying that almost all the genetic variability for these traits is due to QTL located in the chromosomal regions indicated by the analysis. Most of the QTL identified relate to either one trait or the other, which suggests that they are genetically controlled by specific sets of genes.
60 citations