Late Landraces Research Articles

Evolution of Neutral and Flowering Genes along Pearl Millet (Pennisetum glaucum) Domestication

BackgroundPearl millet landraces display an important variation in their cycle duration. This diversity contributes to the stability of crop production in the Sahel despite inter-annual rainfall fluctuation. Conservation of phenological diversity is important for the future of pearl millet improvement and sustainable use. Identification of genes contributing to flowering time variation is therefore relevant. In this study we focused on three flowering candidate genes, PgHd3a, PgDwarf8 and PgPHYC. We tested for signatures of past selective events within polymorphism patterns of these three genes that could have been associated with pearl millet domestication and/or landraces differentiation. In order to implement ad hoc neutrality tests, a plausible demographic history of pearl millet domestication was inferred through Approximate Bayesian Computation by using eight neutral STS loci.ResultsDomesticated pearl millet exhibited 84% of the nucleotide diversity level found in the wild population. No specific polymorphisms were found either in the wild or in the domestic populations. The Bayesian approach and previous studies suggest that gene flow between wild relatives and domesticated pearl millets is a main factor explaining these results. Early and late landraces did not show significant genetic differentiation at both the neutral and the candidate loci. A positive selection was evidenced in PgHd3a and PgDwarf8 genes of domestic forms but not in the wild population.ConclusionOur results strongly suggest that PgHd3a and PgDwarf8 were likely targeted by selection during domestication. However, a potential role of any of the three candidate genes in the phenological differentiation between early and late landraces was not supported by our data. Reasons why these results contrast with previous results that have shown a slight but significant association between PgPHYC polymorphisms and variation in flowering time in pearl millet are discussed.

Evolutionary dynamics of cycle length in pearl millet: the role of farmer’s practices and gene flow

In the Sahel of Africa, farmers often modify their cultivation practices to adapt to environmental changes. How these changes shape the agro-biodiversity is a question of primary interest for the conservation of plant genetic resources. We addressed this question in a case study on pearl millet in south western Niger where farmers used to cultivate landraces with different cycle length in order to cope with rain uncertainty. Early and late landraces were previously grown on distant fields. Nowadays, mostly because of human population pressure and soil impoverishment, it happens that the two types of landraces are grown on adjacent fields, opening the question whether gene flow between them may occur. This question was tackled through a comparative study among contrasting situations pertaining to the spatial distribution of early and late landraces. Observations of flowering periods showed that pollen flow between the two landraces is possible and has a preferential direction from early to late populations.

Yield performance of the European Union Maize Landrace Core Collection under multiple corn borer infestations

In Europe, corn borer attack is the main biotic stressor for the maize ( Zea mays L.) crop. European corn borer ( Ostrinia nubilalis Hbn.) is the most important maize pest in central and north Europe, while pink stem borer ( Sesamia nonagrioides Lef.) is predominant in warmer areas of southern Europe. The objective of this study was the evaluation of the European Maize Union Landrace Core Collection (EUMLCC) for yield under infestation with European corn borer ( O. nubilalis) and pink stem borer ( S. nonagrioides). Eighty-five landraces from Germany, Spain, France, Greece, Italy, and Portugal were evaluated, under corn borer infestation, for yield, grain moisture, and days to flowering at two locations in Spain. Landraces were evaluated separately in four trials that corresponded to four maturity groups. In each maturity group, there were significant differences among landraces for yield of infested plants. Extra-early landraces, ESP0090214, FRA0410010, and ESP0070339; early landraces, FRA0410022, and ESP11985022; midseason landraces, PRT00100392 and ESP11981047; and late landraces, PRT00100569 and PRT00100530, were promising sources of high-yielding maize under corn borer infestation and showed relative earliness within their maturity groups.

Evaluation of the European Union Maize Landrace Core Collection for resistance to Sesamia nonagrioides (Lepidoptera: Noctuidae) and Ostrinia nubilalis (Lepidoptera: Crambidae).

Two corn borer species are the principal maize insect pests in Europe, the European corn borer, Ostrinia nubilalis (Hübner), and the pink stem borer, Sesamia nonagrioides (Lefebvre). Hence, it would be advisable to evaluate the European maize germplasm for corn borer resistance to generate European varieties resistant to corn borer attack. The creation of the European Union Maize Landrace Core Collection (EUMLCC) allowed the screening of most of the variability for European corn borer resistance present among European maize local populations from France, Germany, Greece, Italy, Portugal, and Spain, testing a representative sample. The objective of this study was the evaluation of stem and ear resistance of the EUMLCC to European corn borer and pink stem borer attack. Trials were made at two Spanish locations that represent two very different maize-growing areas. Populations that performed relatively well under corn borer infestation for stem and ear damage were 'PRT0010008' and'GRC0010085', among very early landraces; 'PRT00100120' and 'PRT00100186', among early landraces; 'GRC0010174', among midseason landraces; and 'ESP0070441', among late landraces. Either the selection that could have happen under high insect pressure or the singular origin of determined maize populations would be possible explanations for the higher corn borer resistance of some landraces. Landraces 'PRT0010008', 'FRA0410090', 'PRT00100186', and 'ESP0090214' would be selected to constitute a composite population resistant to corn borers and adapted to short season, whereas populations 'ESP0090033', 'PRT00100530', 'GRC0010174', and 'ITA0370005' would be used to make a resistant composite adapted to longer season.