Varietal data from 27 crop species from five continents were drawn together to determine overall trends in crop varietal diversity on farm. Measurements of richness, evenness, and divergence showed ...that considerable crop genetic diversity continues to be maintained on farm, in the form of traditional crop varieties. Major staples had higher richness and evenness than nonstaples. Variety richness for clonal species was much higher than that of other breeding systems. A close linear relationship between traditional variety richness and evenness (both transformed), empirically derived from data spanning a wide range of crops and countries, was found both at household and community levels. Fitting a neutral "function" to traditional variety diversity relationships, comparable to a species abundance distribution of "neutral ecology," provided a benchmark to assess the standing diversity on farm. In some cases, high dominance occurred, with much of the variety richness held at low frequencies. This suggested that diversity may be maintained as an insurance to meet future environmental changes or social and economic needs. In other cases, a more even frequency distribution of varieties was found, possibly implying that farmers are selecting varieties to service a diversity of current needs and purposes. Divergence estimates, measured as the proportion of community evenness displayed among farmers, underscore the importance of a large number of small farms adopting distinctly diverse varietal strategies as a major force that maintains crop genetic diversity on farm.
•We study phosphorus (P) uptake and utilization efficiency in pearl millet inbreds.•Seedling and mature plants varied significantly for both P efficiency traits.•P utilization increased under low P; ...P uptake was more important for grain production.•The right balance of both traits is needed for sustainable performance under low P.•Breeding for low-P tolerance should be integrated with system-oriented research.
Pearl millet Pennisetum glaucum (L.) R. Br production on the acid sandy Sahelian soils in West Africa (WA) is severely limited by low plant-available phosphorus (P) in addition to erratic rainfall. We sought to examine the genetic variability for P uptake and P utilization efficiency in 180 WA pearl millet inbred lines or subsets thereof under low (LP) and high P (HP) conditions in one field and two pot experiments, determine the relationships among the measured traits and grain yield under field conditions at three other independent WA sites, and identify potential secondary selection traits for improving grain yield under LP. We observed genetic variation for P uptake and utilization in both seedling and mature plants. P utilization efficiency increased under LP conditions. Total P uptake was more important for grain production than P utilization under LP field conditions (r=0.57*** vs r=0.30***). The estimated response to indirect selection was positive for most of the measured morphological and P-efficiency parameters. We conclude that both seedling and mature plant traits are potentially useful as secondary traits in selection of pearl millet for low-P adaptation. These results should be validated using heterozygous pearl millet genetic materials. Ultimately, pearl millet breeding activities for low P tolerance in WA should be integrated with other system-oriented research such as nutrient cycling, intercropping or rotations with legumes, better crop-tree-livestock integration, and modest applications of locally available rock phosphate.
•Adapted pearl millet hybrids could contribute to food security in West Africa (WA).•Heterosis in population hybrids indicated great potential for hybrid breeding in WA.•Hybrids based on ...inter-country crosses did not differ from intra-country crosses.•Lack of natural heterotic groups requires systematic combining ability studies.
Pearl millet (Pennisetum glaucum (L.) R. Br.) is an important hybrid crop in India. However, to date limited pearl millet hybrid development has been undertaken in West Africa (WA), which is the center of pearl millet origin and diversity and where this crop is most important outside India. Using a diverse set of WA pearl millet germplasm, objectives of this study were to determine the superiority of population hybrids over open-pollinated varieties for agro-morphological and agronomic traits in WA pearl millet germplasm; and (ii) to derive strategies for pearl millet hybrid breeding in WA, based on quantitative-genetic parameters, combining ability and heterotic patterns among geographically close versus distant pearl millet populations. A 10×10 factorial mating design was performed with four parental OPVs from each of five WA countries. The 100 population hybrids and their parents were tested for 14 traits at six locations in one year, thereby using contrasting locations to indirectly sample the rainfall variability inherent to WA pearl millet production environments. Grain yield showed an average panmictic midparent heterosis (PMpH) of 16.7%, ranging from −26 to 73%. The mean grain yield of hybrids based on inter-country crosses did not differ significantly from intra-country crosses. Geographic distance between parents was positively correlated with hybrid grain yield (r=0.31), but not with PMpH . Some crosses between accessions from Niger/Nigeria and Senegal were outstanding. Predictability of population hybrid performance for grain yield was moderate based on midparent values (r=0.43) and slightly better based on general combining ability (GCA) (r=0.56). Overall, pearl millet hybrid breeding in WA seems very promising, but there do not seem to be clear “natural” heterotic groups among WA pearl millet landraces. Such heterotic groups as the basis of sustainable hybrid breeding need rather to be created systematically, by building on existing combining ability patterns and aiming to maximize combining ability between the groups.
Aims Pearl millet Pennisetum glaucum (L.) R. Br. open-pollinated varieties, which are the predominant cultivars, have never been systematically evaluated for adaptation to low-soil phosphorus (P), a ...major constraint on pearl millet production in West Africa (WA). Methods We evaluated grain yield (GY), flowering time (FLO), harvest index (HI), and residual grain yields (RGY) of 102 open-pollinated varieties from WA under low-P (–P) and high-P (+P) field conditions in six environments of WA. In addition, PE-related traits of the varieties were evaluated at early growth stage in a pot experiment. Results Significant genetic variation was observed for GY, FLO, HI and PE-related traits. P-efficient varieties had higher yield under –P conditions. Varietal performance under –P varied across environments depending on FLO, relative flowering delay under –P (FD) and RGY measured in the field. Low-P-susceptible varieties had higher FLO, lower HI than low-P-tolerant varieties. Response to direct selection under –P field conditions was 20.1 g m⁻², whereas indirect selection response under +P was 16.3 g m⁻² . Conclusions Selection under –P field conditions while taking into account seasonal variations for FLO, FD and PE is expected to be important for improving GY specifically targeting –P environments in WA.
ABSTRACT
Pearl millet Pennisetum glaucum (L.) R. Br is a food security crop for millions living in drylands of Africa and Asia. Its production on acid sandy soils of the Sahel is limited by erratic ...rainfall and poor soil fertility, especially low P soils. We sought to elucidate the genetic variation in West and Central African landrace‐derived inbred lines for grain yield under low P conditions, to determine their performance as inbred lines per se and in hybrid combinations, and to determine quantitative‐genetic parameters to derive an appropriate breeding strategy to enhance grain yield under low P conditions. We evaluated a total of 155 landrace‐derived inbred lines as well as their testcrosses in four locations during two years under two treatments, high P (HP; with P fertilization) and low P (LP; without P fertilization). Results revealed significant effects for genotypes, P‐level, genotype × P‐level, as well as genotype × environment interactions. Grain yield reductions under LP treatment ranged from 7.9 to 35.5%, and 11.2 to 60.9% for inbred lines and testcrosses respectively, with positive midparent heterosis averaging 43.5% under LP. We conclude that direct selection of testcrosses under LP is more effective and that indirect selection for testross performance from inbred line performance is not desirable.
ABSTRACT
Pearl millet Pennisetum glaucum (L.) R. Br. was domesticated in Sahelian West Africa. This highly outcrossing crop is one of the most important staple cereals in the semiarid tropics, ...adapted to very harsh rain‐fed conditions. Agro‐morphological characterization of local germplasm is very important to better understand existing diversity, ease targeted genetic broadening of breeding populations, and potentially link this knowledge to genotypic information. The objectives of our study were to (i) characterize West and Central African (WCA) pearl millet accessions based on their agro‐morphological traits; (ii) evaluate the possibility to group accessions based on their agro‐morphological characteristics; (iii) determine geographic patterns of phenotypic differentiation; and (iv) derive conclusions for pearl millet improvement in WCA. A total of 360 early‐to‐medium maturity accessions were phenotyped for 12 agro‐morphological traits at six environments in WCA. Wide ranges of all observed traits indicated a high diversity of the tested accessions. Principal component analysis revealed very large diversity within individual countries, especially within Mali and Burkina Faso. Some limited grouping of accessions from Niger, Senegal, Cameroon, Morocco, and Mauritania was observed for individual principal component axes. Geographical differentiation and country differences were detected for several traits. The results and data presented in our study reflect WCA pearl millets’ tremendous diversity and adaptability to a wide range of environments and give a sound basis for breeders to select and utilize this germplasm to serve the manifold needs of WCA pearl millet farmers.
Au Burkina, les ressources génétiques du mil jouent un grand rôle dans la production agricole et participent de manière significative à la sécurité alimentaire. La production du mil dans le pays est ...assurée en grande partie par les écotypes locaux issus des techniques de sélection paysannes et dont les analyses agromorphologiques et enzymatiques ont montré la très grande variabilité génétique. Depuis ces 30 dernières années, la situation a changé au détriment de cette variabilité. En effet, avec les cycles successifs de sécheresse depuis les années 1970 et la pression de plus en plus forte sur les ressources naturelles d’une population en croissance rapide, on assiste à la dégradation des écosystèmes, à l’appauvrissement des sols et à la disparition d’un certain nombre de cultivars conduisant ainsi à l’érosion génétique. Malgré l’importance des ressources génétiques du mil et les problèmes mentionnés, il n’existe pas encore de politique spécifique en faveur de leur conservation et de leur utilisation adéquate. Quelques approches et stratégies mises en œuvre ont permis cependant de mener des activités de recherche sur les ressources phytogénétiques, permettant ainsi de garantir un tant soit peu leur conservation ex et in situ, et également leur utilisation dans les programmes d’amélioration variétale. Cette stratégie est basée sur le partenariat avec un certain nombre d’institutions intéressées par les ressources phytogénétiques. Il s’agit pour la conservation ex situ , notamment, des instituts français (IRAT, IRD), et des instituts internationaux (IPGRI, FAO, ICRISAT). Ainsi, avec ces partenaires, le Burkina a pu réaliser la prospection et la collecte sur l’ensemble du territoire de tout le matériel génétique du mil, formes cultivées et sauvages. Au total, 1 570 échantillons de mil dont 3 formes sauvages ont été collectés de 1960 à 1999 dont la plupart sont conservés par l’ICRISAT (Inde), l’IRD (France) et le CIRP (Canada). Les échantillons légués au Burkina sont conservés à la station de recherche de Farako Bâ et utilisés dans le programme de sélection après évaluation. Au cours des dernières années, la réalisation d’un certain nombre de projets a permis d’analyser les connaissances et les savoir-faire paysans dans la conservation in situ de l’agrobiodiversité du mil. De même, il a été étudié les flux de gènes et les introgressions entre formes sauvages et cultivées. Dans le cadre de cette stratégie, le Burkina a signé également tous les accords et conventions internationaux, régionaux et sous-régionaux sur la protection des ressources biologiques, dont le plus récent est le Protocole de Cartagena sur la prévention des risques biotechnologiques. Des textes relatifs à la mise en place d’un cadre national sur les ressources phytogénétiques sont élaborés et en cours de finalisation. L’adoption de ces textes permettra de prendre en compte de manière spécifique la problématique « ressources phytogénétiques » dans la politique de recherche au Burkina.
Pearl millet genetic resources play an important role in crop production and food security in Burkina Faso. Most of millet varieties planted every year are originated from landraces developed through farmers’ traditional breeding techniques. Agromorphological and enzymatic data analyses show high levels of genetic variability in local millet ecotypes. Over the last three decades, this variability was affected by multiple unfavourable factors like repeated cycles of drought and human pressure on natural resources. The consequences of this situation are ecosystems degradation, low soil fertility, disappearance of long cycle cultivars and genetic erosion. To address this problem, a large number of countries developed policies to conduct phytogenetic resources research programmes. Despite their importance, Burkina Faso has not yet a specific policy for millet genetic resources. But some approaches and strategies based on partnership for ex and in situ conservation are taken into account. Ex situ conservation in Burkina involved germplasm collection through out the country with IRAT, IRD (ex ORSTOM), IPGRI, FAO, ICRISAT. From 1960 to 1999, more than 1570 samples of pearl millet ecotypes included 3 wild types were collected. This germplasm is conserved at ICRISAT (India), IRD (France) and ICPR (Canada). Agromorphological and enzymatic evaluations were done on the genetic material. Some samples are conserved in freezers at Farako-Bâ research station and used in the national breeding programme. In situ conservation research has been developed over the last seven years (1996). These research activities studied farmers’ knowledge related to agrobiodiversity conservation and management. One of the project activities analyses gene flow and genetic introgression between cultivated and wild millet types. Burkina Faso signed a large number of international, regional and sub-regional conventions and agreements related to the preservation and management of biologic resources. The last one is the Cartagena Protocole for biosafety. In 2002, Burkina Faso began to elaborate a national framework for phytogenetic resources.
Au Burkina, les ressources génétiques du mil jouent un grand rôle dans la production agricole et participent de manière significative à la sécurité alimentaire. La production du mil dans le pays est ...assurée en grande partie par les écotypes locaux issus des techniques de sélection paysannes et dont les analyses agromorphologiques et enzymatiques ont montré la très grande variabilité génétique. Depuis ces 30 dernières années, la situation a changé au détriment de cette variabilité. En effet, avec les cycles successifs de sécheresse depuis les années 1970 et la pression de plus en plus forte sur les ressources naturelles d’une population en croissance rapide, on assiste à la dégradation des écosystèmes, à l’appauvrissement des sols et à la disparition d’un certain nombre de cultivars conduisant ainsi à l’érosion génétique. Malgré l’importance des ressources génétiques du mil et les problèmes mentionnés, il n’existe pas encore de politique spécifique en faveur de leur conservation et de leur utilisation adéquate. Quelques approches et stratégies mises en œuvre ont permis cependant de mener des activités de recherche sur les ressources phytogénétiques, permettant ainsi de garantir un tant soit peu leur conservation ex et in situ, et également leur utilisation dans les programmes d’amélioration variétale. Cette stratégie est basée sur le partenariat avec un certain nombre d’institutions intéressées par les ressources phytogénétiques. Il s’agit pour la conservation ex situ , notamment, des instituts français (IRAT, IRD), et des instituts internationaux (IPGRI, FAO, ICRISAT). Ainsi, avec ces partenaires, le Burkina a pu réaliser la prospection et la collecte sur l’ensemble du territoire de tout le matériel génétique du mil, formes cultivées et sauvages. Au total, 1 570 échantillons de mil dont 3 formes sauvages ont été collectés de 1960 à 1999 dont la plupart sont conservés par l’ICRISAT (Inde), l’IRD (France) et le CIRP (Canada). Les échantillons légués au Burkina sont conservés à la station de recherche de Farako Bâ et utilisés dans le programme de sélection après évaluation. Au cours des dernières années, la réalisation d’un certain nombre de projets a permis d’analyser les connaissances et les savoir-faire paysans dans la conservation in situ de l’agrobiodiversité du mil. De même, il a été étudié les flux de gènes et les introgressions entre formes sauvages et cultivées. Dans le cadre de cette stratégie, le Burkina a signé également tous les accords et conventions internationaux, régionaux et sous-régionaux sur la protection des ressources biologiques, dont le plus récent est le Protocole de Cartagena sur la prévention des risques biotechnologiques. Des textes relatifs à la mise en place d’un cadre national sur les ressources phytogénétiques sont élaborés et en cours de finalisation. L’adoption de ces textes permettra de prendre en compte de manière spécifique la problématique « ressources phytogénétiques » dans la politique de recherche au Burkina.
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