Interactions of inbreeding and stress by poor host quality in a root hemiparasite

Striga gesnerioides is a root hemiparasite that primarily parasitizes dicotyledonous species, including cowpea ( Vigna unguiculata L.) and other legumes. Based on the differential resistance response of various cultivars, landraces, and breeding lines, it has been proposed that several distinct races of cowpea-parasitic S. gesnerioides exist in West Africa. In this study, we used amplified fragment length polymorphism profile analysis to examine the genetic variability within and among populations of cowpea-parasitic S. gesnerioides within the suspected distribution range of a particular race, and statistical clustering methods to define the phenetic relationships of the various races in West Africa. Our data indicate that genetic variability within and among populations of each of the previously recognized races of cowpea-parasitic S. gesnerioides is extremely low. On the basis of genotypic profile and host differential resistance responses, 2 previously unknown races were identified. Of the 7 races now identifiable, races SG1 (from Burkina Faso) and SG5 (from Cameroon) are the most closely related, and SG4 (from Benin) and SG3 (from Niger/Nigeria) are the most divergent. SG6, a new race of the parasite identified in Senegal, was found to be the most genetically similar to SG4 from Benin. We also demonstrate that a hypervirulent isolate of the S. gesnerioides from Zakpota, in the Republic of Benin, is genotypically distinct from other populations of SG4, thereby warranting designation as a separate race, which we called SG4z. To further support our race classification scheme, we identified a group of molecular markers that effectively discriminate each of the various races. Finally, we show that an isolate (designated SG4i) of the wild legume Indigofera hirsuta –parasitic S. gesnerioides is genetically distinct and significantly diverged from the various races of cowpea-parasitic S. gesnerioides. Our data suggest that both geographic isolation and host-driven selection are critical factors defining race formation in S. gesnerioides in West Africa.

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Peer Review #2 of "Brood size and sex ratio in response to host quality and wasp traits in the gregarious parasitoid Oomyzus sokolowskii (Hymenoptera: Eulophidae) (v0.2)"

10.7287/peerj.2919v0.2/reviews/2 ◽

2017 ◽

Keyword(s):

Sex Ratio ◽

Peer Review ◽

Brood Size ◽

Host Quality ◽

Gregarious Parasitoid

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Positive and Negative Interactions among Individuals of a Root Hemiparasite

Plant Biology ◽

10.1055/s-2003-37978 ◽

2003 ◽

Vol 5 (1) ◽

pp. 79-84 ◽

Cited By ~ 11

Author(s):

D. Matthies

Keyword(s):

Root Hemiparasite ◽

Negative Interactions

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Consistency in seed-deposition patterns and the distribution of mistletoes among its host trees in an Amazonian savanna

Australian Journal of Botany ◽

10.1071/bt09013 ◽

2009 ◽

Vol 57 (8) ◽

pp. 640 ◽

Cited By ~ 15

Author(s):

Rodrigo Ferreira Fadini ◽

Danielly Caroline Miléo Gonçalves ◽

Rúbia Patrícia Fernandes Reis

Keyword(s):

Spatial Distribution ◽

Field Experiment ◽

Host Size ◽

Host Quality ◽

Deposition Patterns ◽

Seed Disperser ◽

Crown Diameter ◽

Host Trees ◽

Cashew Tree ◽

To Receive

The present paper describes the spatial distribution of the mistletoe Psittacanthus plagiophyllus Eichl. (Loranthaceae) on its host, the cashew tree Anacardium occidentale L., in a Brazilian Amazonian savanna. Our aim was to understand the roles of bird-seed dispersers and host quality in determining the mistletoe distribution among its host trees. In 2006, we marked 118 cashews in a 4.5-ha plot and counted the number of mistletoes and the presence of seeds attached to host branches in 2006, 2007 and 2008. On average, 36% of the hosts were infected each year. The infection load and the probability of being infected increased significantly with host crown diameter. On average, 25% of the hosts received at least one mistletoe seed in each year, being taller and previously infected hosts more prone to receive seeds in all 3 years. Elaenia cristata was the main seed disperser, visiting P. plagiophyllus 48 times in 35 h of focal records. Additionally, in a field experiment, we used the presence of an infection and the host size as surrogates for host quality and tested their effect on mistletoe survivorship. After 9 months, 16.5% of seeds survived and 14% had established, but neither host conditions nor host size influenced seed survivorship. Therefore, we suggest that mistletoe distribution is a consequence of a consistent dispersal of seeds onto larger and previously parasitised hosts across years.

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Influence of Plant Host Quality on Fitness and Sex Ratio of the Wheat Stem Sawfly (Hymenoptera: Cephidae)

Environmental Entomology ◽

10.1603/0046-225x-34.6.1579 ◽

2005 ◽

Vol 34 (6) ◽

pp. 1579-1592 ◽

Cited By ~ 30

Author(s):

H. A. Cárcamo ◽

B. L. Beres ◽

F. Clarke ◽

R. J. Byers ◽

H.-h. Mündel ◽

...

Keyword(s):

Sex Ratio ◽

Host Quality ◽

Plant Host ◽

Wheat Stem Sawfly

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INVITATION PAPER: C.P. Alexander Fund: HOST CHOICE BY APHIDIID PARASITOIDS (HYMENOPTERA: APHIDIIDAE): HOST RECOGNITION, HOST QUALITY, AND HOST VALUE

The Canadian Entomologist ◽

10.4039/ent128959-6 ◽

1996 ◽

Vol 128 (6) ◽

pp. 959-980 ◽

Cited By ~ 86

Author(s):

M. Mackauer ◽

J.P. Michaud ◽

W. Völkl

Keyword(s):

Host Choice ◽

Growth Potential ◽

Physical Contact ◽

Response Threshold ◽

Host Recognition ◽

Egg Load ◽

Host Quality ◽

State Variables ◽

Female Progeny ◽

Potential Host

AbstractSpecies in the family Aphidiidae (Hymenoptera) parasitize exclusively ovoviviparous aphids. Females use a variety of information to detect and evaluate suitable hosts. Olfactory cues associated with aphids, or the aphids’ host plant, are important for host location. Visual cues including aphid colour, shape, and movement can be evaluated from a distance without physical contact; aphid movement may act as a releasing stimulus for attack. Contact chemosensory cues (gustatory cues) are evaluated by antennation of the host cuticle and during ovipositor probing. A potential host must conform to the wasp’s response profile and satisfy minimum physiological and dietary requirements for immature development and growth. Host quality is determined in part by attributes specific to each aphid species and in part by each aphid’s individual-specific growth potential. Host quality for male and female progeny may vary as a result of different patterns of resource allocation and sexual size dimorphism. For an encountered aphid to be accepted as a host, its perceived value must exceed the wasp’s response threshold for oviposition. Host value, as opposed to host quality, varies dynamically with parasitoid state variables such as age, egg load, and prior experience. A conceptual model of host choice by aphidiid wasps is presented.

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