Gametophytic competition as influencing gene flow between wild and cultivated forms of pearl millet (Pennisetum typhoides)

Genome ◽  
1991 ◽  
Vol 34 (2) ◽  
pp. 195-200 ◽  
Author(s):  
T. Robert ◽  
R. Lespinasse ◽  
J. Pernès ◽  
A. Sarr
Keyword(s):  
Gene Flow ◽  
Pearl Millet ◽  
Competitive Ability ◽  
Inbred Lines ◽  
Cultivated Plants ◽  
Sympatric Populations ◽  
Pennisetum Typhoides ◽  
Allopatric Populations ◽  
Land Race ◽  
Almost All

Intergametophytic competitions with prepotency of autopollen have been previously described in some cultivated lines of pearl millet (Pennisetum typhoides (Burm.) Stapf &Hubb.). This paper reports the analysis of intergametophytic competitions between pollen from wild and cultivated plants on stigmas of both wild and cultivated plants. Three inbred lines (two cultivated and one wild) and two land races (one cultivated and one wild) were used, each of them as pollen donors as well as plant receptors. These populations represent in some instances allopatric and sympatric evolutionary situations between wild and cultivated forms. Deviations from the equiprobability of gamete encounters for almost all progeny are clearly demonstrated and reveal a large amount of male gametophytic fitness variability in land-race populations. There is no marked hierarchy between pollen sources for their competitive ability, but taking into account the pollen-pistil interactions, preferential wild-wild and cultivated-cultivated gamete associations are noticeable. Thus, pollen competitions establish a fine reproductive limit between allopatric populations as well as between wild and cultivated sympatric populations. This soft reproductive "barrier" controls the gene flow between adjacent populations and could explain the success of pearl millet domestication, allowing the wild and cultivated types to keep their phenotypic integrity despite the gene flow.Key words: pearl millet, intergametophytic competitions, gene flow, domestication.

Spatial variation in susceptibility to infection in a snail–trematode interaction

Parasitology ◽  
2000 ◽  
Vol 121 (4) ◽  
pp. 395-401 ◽  
Author(s):  
A. C. KRIST ◽  
C. M. LIVELY ◽  
E. P. LEVRI ◽  
J. JOKELA
Keyword(s):  
Gene Flow ◽  
Shallow Water ◽  
Local Adaptation ◽  
Deep Water ◽  
Clinal Variation ◽  
Sympatric Populations ◽  
Host Condition ◽  
Susceptibility To Infection ◽  
Allopatric Populations ◽  
Asymmetric Pattern

Parasites should be better at infecting hosts from sympatric populations than allopatric populations most of the time (parasite local adaptation). In a previous study of a population of snail parasites (Microphallus sp.) from Lake Alexandrina, New Zealand, we found that Microphallus was more infective to snails (Potamopyrgus antipodarum) in shallow water but not in deep water. Here, we repeated the original study and also monitored the development of the parasite. We found that parasites from shallow water were more infective to hosts from shallow water and developed more rapidly in these hosts. In contrast, parasites from deep water were not more infective to hosts from deep water and did not develop more rapidly in them. These results suggest clinal variation in the susceptibility of these snails, with shallow-water snails more susceptible than deep-water snails. We offer 2 possible explanations for these results. First, gene flow in the Microphallus population is primarily from shallow to deep water, leading to an asymmetric pattern of local adaptation. Alternatively, snails from shallow water may be more susceptible for reasons independent of gene flow, perhaps due to differences in host condition between habitats.

scholarly journals Premating barriers in young sympatric snail species

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Arina L. Maltseva ◽  
Marina A. Varfolomeeva ◽  
Arseniy A. Lobov ◽  
Polina O. Tikanova ◽  
Egor A. Repkin ◽  
...  
Keyword(s):  
Gene Flow ◽  
Snail Species ◽  
Sympatric Populations ◽  
Gastropod Species ◽  
Shell Size ◽  
Closely Related Species ◽  
Partial Canonical Correspondence Analysis ◽  
In The Wild ◽  
Isolation Index

AbstractSympatric coexistence of recently diverged species raises the question of barriers restricting the gene flow between them. Reproductive isolation may be implemented at several levels, and the weakening of some, e.g. premating, barriers may require the strengthening of the others, e.g. postcopulatory ones. We analysed mating patterns and shell size of mates in recently diverged closely related species of the subgenus Littorina Neritrema (Littorinidae, Caenogastropoda) in order to assess the role of premating reproductive barriers between them. We compared mating frequencies observed in the wild with those expected based on relative densities using partial canonical correspondence analysis. We introduced the fidelity index (FI) to estimate the relative accuracy of mating with conspecific females and precopulatory isolation index (IPC) to characterize the strength of premating barriers. The species under study, with the exception of L. arcana, clearly demonstrated preferential mating with conspecifics. According to FI and IPC, L. fabalis and L. compressa appeared reliably isolated from their closest relatives within Neritrema. Individuals of these two species tend to be smaller than those of the others, highlighting the importance of shell size changes in gastropod species divergence. L. arcana males were often found in pairs with L. saxatilis females, and no interspecific size differences were revealed in this sibling species pair. We discuss the lack of discriminative mate choice in the sympatric populations of L. arcana and L. saxatilis, and possible additional mechanisms restricting gene flow between them.

The Use of Protein Electrophoresis for Determining Species Boundaries in Amphipods

Crustaceana ◽  
1993 ◽  
Vol 65 (2) ◽  
pp. 265-277 ◽  
Author(s):  
Barbara A. Stewart
Keyword(s):  
Gene Flow ◽  
Genetic Differentiation ◽  
Morphological Variation ◽  
Protein Electrophoresis ◽  
Species Boundaries ◽  
Allopatric Populations ◽  
A Value ◽  
Electrophoretic Data

AbstractThe use of protein electrophoretic data for determining species boundaries in amphipods is addressed. Analysis of published literature on genetic differentiation in amphipods showed that pairs of allopatric populations which have genetic identities (I) above a value of 0.85 probably represent intraspecific populations, whereas pairs of populations which have genetic identities below about 0.45 probably represent different species. It was recommended that if I values fall between 0.45 and 0.85, additional factors such as evidence of a lack of gene flow between the populations, and concordant morphological variation should be considered.

scholarly journals Cytological Studies of Desynaptic Stock in Pearl Millet, Pennisetum typhoides (Burm.) S. and H

CYTOLOGIA ◽  
1973 ◽  
Vol 38 (2) ◽  
pp. 311-316 ◽  
Author(s):  
Jagtar S. Dhesi ◽  
B. S. Gill ◽  
H. L. Sharma
Keyword(s):  
Pearl Millet ◽  
Pennisetum Typhoides

Sclerospora graminicola. [Descriptions of Fungi and Bacteria].

1983 ◽  
Author(s):  
S. M. Francis
Keyword(s):  
Pearl Millet ◽  
Geographical Distribution ◽  
Pennisetum Glaucum ◽  
Systemic Disease ◽  
Leaf Tissue ◽  
Seed Transmission ◽  
Distal Portion ◽  
Sclerospora Graminicola ◽  
Complete Replacement ◽  
Pennisetum Typhoides

Abstract A description is provided for Sclerospora graminicola. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: The two hosts on which this pathogen causes diseases of major economic importance are Pennisetum typhoides[Pennisetum glaucum] (syn. P. americanum) and Setaria italica. Also recorded on Echinochloa crusgalli, E. crusgalli var. fumentacea, Eleusine indica, Panicum miliaceum, Pennisetum leonis, Saccharum of ficinarum (by inoculation only), Setaria lutescens, S. magna, S. verticillata, S. viridis and Zea mexicana. The disease is very rare on Zea mays with only two confirmed reports, Melhus & Bliss (1928) in the USA and Kenneth (1966) in Israel. DISEASE: Graminicola downy mildew; green ear of pearl millet (Pennisetum typhoides[Pennisetum glaucum]). A biotrophic plant pathogen which invades and colonizes the growing points of young graminaceous plants causing systemic disease. The first leaf to show symptoms is yellowed in the basal portion with a distinct margin between the basal colonized portion and the non colonized distal portion. Leaves formed later show increasing amounts of disease until the entire leaf shows symptoms. Under suitable conditions sporangia form in great profusion on the under surface of the diseased leaf (and, when conditions are favourable, also on the upper surface) forming a conspicuous and characteristic white 'down'. Occasionally discrete local lesions have been observed on otherwise healthy leaves in highly susceptible cultivars in W. Africa. The most distinctive appearance of the disease on pearl millet is, however, the transformation of the inflorescences to vegetative structures with various leaf-like protrusions which vary greatly in size and number from very few on an almost normal inflorescence to complete replacement of the inflorescence by small leafy shoots. As diseased organs mature they become necrotic and often contain oospores within the tissue. In pearl millet the leaves containing oospores do not shred. The areas containing oospores are a deep chocolate brown and usually appear as long stripes down the leaf. On Setaria the symptoms are similar to those observed on pearl millet except that shredding of the leaf tissue containing oospores occurs. In the phase of the disease described above the height of the infected plants differs little from that of healthy plants. Another and less frequent reaction is that the diseased plants are severely stunted, show a yellow mottle, with non-infected parts becoming a much darker green than in healthy plants; few sporangia are produced and no green ears for the plants generally do not head. This reaction is a characteristic response of certain host genotypes. GEOGRAPHICAL DISTRIBUTION: CMI Map 431, ed. 2, 1979. Note that the pearl millet pathotype has not been reported from the Americas. TRANSMISSION: Initial infection is by oospores which may remain viable for up to 10 years (Nene & Singh, 1976). Later infection comes from sporangia developing on early diseased leaves and spread by wind and rain to newly developed tillers which are produced throughout the growth of the plant (Singh & Williams, 1980). Seed transmission occurs from oospores carried with, and on, seed and there are conflicting reports of transmission from mycelium carried within seed (Williams, 1980).

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