Root Hemiparasite Research Articles

Native root hemiparasites form haustorial attachments with multiple invasive and expansive species

Parasitic plants are known for shaping plant communities, mainly by suppressing dominant species. This suppression, in some cases, fosters species coexistence and boosts overall diversity. Recent studies reveal that certain parasitic plants can curb invasive alien plants or expansive native species. In this study, we followed previous case studies, investigating the ability of three common Central European hemiparasitic species to attach to roots and form functional haustoria across a broad range of invasive and expansive hosts. For each host-hemiparasite pair, we posed two questions: (i) Do the hemiparasites produce haustoria on the host's roots or rhizomes? (ii) Does the anatomical structure of the haustoria include all features necessary for their functionality? We cultivated three hemiparasitic species, Melampyrum arvense L., Rhinanthus alectorolophus (Scop.) Pollich, and Odontites vernus subsp. serotinus (Dumort.) Corb., in pots with 18 candidate hosts. After cultivation, we dissected the root systems to determine haustoria abundance and to collect them for anatomical study to assess their functionality. Hemiparasite individuals in each pot were also counted. The hemiparasitic species produced haustoria on the majority of tested hosts (37 out of 44 combinations), with little difference between native expansive and alien invasive plant species. In 13 host-hemiparasite combinations (including eight combinations with invasive species), we identified abundant functional haustoria and good establishment of the hemiparasites. Remarkably, all three hemiparasitic species formed functional haustoria on invasive Asteraceae hosts. By contrast, Melampyrum arvense performed poorly when cultivated with grasses. We identified a series of hemiparasite-host combinations, which should be further tested for the potential hemiparasite effect on host fitness in the field. The abundance and anatomical structure of the haustoria indicates that the recognised low specificity of the hemiparasitic interactions applies also to associations with alien invasive species, with which they do not share a common evolutionary history.

Tradeoffs in access to light and root networks of established host trees for restoration planting of the root hemiparasite Santalum paniculatum

Restoration of root hemiparasite trees, such as Hawaiʻi's endemic Santalum species (ʻiliahi), may benefit from underplanting in stands of suitable hosts like the nitrogen‐fixing native tree, Acacia koa (koa). At a pasture site on Hawaiʻi Island previously reforested with koa, we underplanted seedlings of the island‐endemic sandalwood species, Santalum paniculatum, to examine the tradeoff between access to an established root network (distance to the nearest koa tree) under variable overstory shading (8.8–90.1% canopy openness range) during regeneration establishment. We hypothesized that there is an optimal parasite–host spacing and canopy openness that balance parasitic resource transfer with light availability. ʻIliahi seedling survival was 96% with no survival treatment differences. ‘Iliahi seedling growth was positively related to canopy openness but negatively related to the distance to the nearest koa tree, and the slope of these relationships increased over time. Leaf photosynthetic light compensation points, light saturation points, and stomatal density mostly followed similar trends as growth. These results demonstrate that ‘iliahi can be successfully underplanted in an established koa stand, which benefits ‘iliahi plantings and contributes to diversifying initial restoration and reforestation plantings. There appears to be a significant tradeoff in planting distance between benefits from and competition with the host; however, the improvement in growth with increased canopy openness appeared to be much greater than the effect of planting distance. Underplanting into an established host stand with sufficient canopy openness can help restore functionally compatible and abundant ‘iliahi regeneration into forests.

Local adaptation of a generalist hemiparasitic plant to one of its potential host plants

Coevolution is often found in parasite–host interactions, but has not yet been described for hemiparasitic plants and their hosts. Root hemiparasites like Rhinanthus alectorolophus perform photosynthesis but also parasitize other plant species, some of which (e.g. Plantago lanceolata) may defend themselves against parasite attack by blocking the haustoria of the parasites. We grew seedlings of the hemiparasite R. alectorolophus and the potential host P. lanceolata from seven grassland sites in a factorial design. To detect differences in host defence, we also included hosts from two ‘naïve' populations from regions where the parasite does not occur. R. alectorolophus grew consistently larger and had higher fitness with sympatric than with allopatric hosts, suggesting parasite adaptation to local host populations. Moreover, R. alectorolophus remained smallest with allopatric hosts from the same region and reached intermediate sizes with allopatric hosts from other regions or naïve hosts, suggesting host adaptation to parasites at the regional scale. Parasite presence reduced the size of the host plants already after four weeks, but only that of hosts with ‘experience' of the parasite, suggesting an early host response. Follow‐up experiments confirmed that parasites attach to hosts already after four weeks and hosts respond by changing belowground allocation patterns. However, parasite roots did not preferentially grow towards sympatric hosts. Our results suggest that local adaptation to hosts can occur even in generalist parasites and does not require specialization on individual hosts. We discuss the role of potential mechanisms, including variation in chemical signalling (early) and in host defence (late effects).

Delineating the role of host plants in regulating the water and salinity stress induced changes in sandalwood roots.

The interaction of root hemi-parasite (sandalwood) with its hosts is crucial for establishing successful plantations under abiotic stresses. In the present study, we explored the best possible host for sandalwood along with its effect on sandalwood physiology in terms of water and nutrients. Interactive effects of host species (Alternanthera sp., Azadirachta indica, Dalbergia sissoo, Melia dubia, and Aquilaria malaccensis) with sandalwood were observed under eight treatments {100% best available water (BAW); 100% BAW + nutrient medium; 50% water deficit; 50% water deficit + nutrient medium; 100% saline water (ECiw 8ds/m); 100% saline water (ECiw 8ds/m) + nutrient medium; 50% water deficit + saline water (ECiw 8ds/m); and 50% water deficit + saline water (ECiw 8ds/m) + nutrient medium}. A significant change in morpho-physiological traits of sandalwood roots was observed under different stress conditions, which were slightly improved through external supply of nutrient medium. Dalbergia sissoo (Shisham) and Melia dubia (Dek) seemed to be the best host plants providing better environment for sandalwood growth and development, i.e., higher plant height (59.7 and 53.68cm) and collar diameter (3.24 and 3.07mm) under stresses by maintaining water and ionic balance. Root length is an important parameter that was reduced by 27.58%, 19.22%, and 36.3% under water deficit, salinity, and combined stress of water deficit and salinity. Sandalwood grown with D. sissoo and M. dubia maintained the lowest Ψw (-1.38MPa) and Ψs (-1.47 and -1.48MPa), respectively. In addition, sandalwood cultivated with D. sissoo and A. indica had higher accumulation of soluble proteins (0.48 and 0.42mg/g) and soluble sugars (98.56 and 91.04mg/g) in their roots. Results also showed that sandalwood roots had higher K+/Na+ with compatible host, i.e., with A. indica (1.85) and D. sissoo (1.83) than other studied hosts. It was also observed that sandalwood plants could not grow and survive alone under stress conditions even with application of nutrient medium. Based on the morphological traits, it was observed that sandalwood grown with hosts, Dalbergia sissoo and Melia dubia, was able to tolerate stress conditions better than other studied hosts. We can further recommend growing sandalwood with D. sissoo and M. dubia as a viable option to endure adverse environmental conditions.

Hemiparasite Phtheirospermum japonicum growth benefits from a second host and inflicts greater host damage with exogenous N supply

While parasites are likely to connect to multiple host plants in nature, parasitism dynamics under multiple association conditions remain unclear and are difficult to separate from competitive effects. In this study, a five-compartment split root-box was constructed to allow a single facultative root hemiparasite, Phtheirospermum japonicum, to connect to zero, one or two Medicago sativa hosts while maintaining constant plant number and independently controlling nutrient supply. In the first experiment, we found that P. japonicum derived equal, additive benefits from attachment to a second host irrespective of parasite N status. In the second experiment, parasites were grown at four N levels in either parasitic or control conditions. Attachment caused a constant, absolute increase in parasite mass at all N levels, while host damage increased at higher parasite N levels despite an apparent decrease in host to parasite N transfer. Our findings suggest that host damage caused by P. japonicum may be strengthened by exogenous nitrogen supply to the parasite.

Effects of Hemiparasites in Grassland Restorations Are Not Universal

Root hemiparasites infiltrate the vascular tissue of host roots to acquire water and nutrients, which often reduces host growth. Hemiparasites are postulated to be keystone species in grassland communities if they suppress dominant species and increase plant community biodiversity, and ecosystem engineers if they increase nutrient accessibility for surrounding species. We examined keystone effects by evaluating species richness and evenness in 1 m2 plots in a recent prairie restoration where Castilleja sessiliflora was naturally present or absent, and in a longer-established prairie restoration with or without Pedicularis canadensis. We examined ecosystem engineer effects by determining nitrate and phosphate concentrations under, 25 cm from, and 50 cm from hemiparasites, and in the center of hemiparasite-free plots. On the C. sessiliflora site, plots with the hemiparasites had higher species richness due to more forbs and higher floristic quality, consistent with the keystone species hypothesis. Soil phosphate levels were also greater in plots with C. sessiliflora present, consistent with the hypothesis of ecosystem engineering by this hemiparasite. In contrast, plots with/without P. canadensis showed no associations of any community metrics with the hemiparasite, and no correspondence between the presence of hemiparasites and soil nutrients. Although hemiparasites can increase grassland community heterogeneity, the effect is not universal, and the direction and strength of effects likely depends on local conditions.

Controlled Transition in a Modified Model of Biomass Dynamics of Root Hemiparasitic Plants

Controlled Transition in a Modified Model of Biomass Dynamics of Root Hemiparasitic Plants

Root hemiparasites suppress invasive alien clonal plants: evidence from a cultivation experiment

Alien invasive plants threaten biodiversity by rapid spread and competitive exclusion of native plant species. Especially, tall clonal invasives can rapidly attain strong dominance in vegetation. Root-hemiparasitic plants are known to suppress the growth of clonal plants by the uptake of resources from their below-ground organs and reduce their abundance. However, root-hemiparasites’ ability to interact with alien clonal plants has not yet been tested. We explored the interactions between native root-hemiparasitic species, Melampyrum arvense and Rhinanthus alectorolophus and invasive aliens, Solidago gigantea and Symphyotrichum lanceolatum. We investigated the haustorial connections and conducted a pot experiment. We used seeds from wild hemiparasite populations and those cultivated in monostands of the invasive plants to identify a possible selection of lineages with increased compatibility with these alien hosts. The hemiparasitic species significantly suppressed the growth of the invasive plants. Melampyrum inflicted the most substantial growth reduction on Solidago (78%), followed by Rhinanthus (49%). Both hemiparasitic species reduced Symphyotrichum biomass by one-third. Additionally, Melampyrum reduced the shoot density of both host species. We also observed some transgenerational effects possibly facilitating the growth of hemiparasites sourced from subpopulations experienced with the host. Native root hemiparasites can effectively decrease alien clonal plants’ biomass production and shoot density. The outcomes of these interactions are species-specific and may be associated with the level of clonal integration of the hosts. The putative selection of lineages with higher performance when attached to the invasive novel hosts may increase hemiparasites’ efficiency in future biocontrol applications.

Effect of Epichloë Endophyte on the Growth and Carbon Allocation of Its Host Plant Stipa purpurea under Hemiparasitic Root Stress.

Epichloë endophytes not only affect the growth and resistance of their host plants but also confer nutrient benefits to parasitized hosts. In this study, we used Pedicularis kansuensis to parasitize Stipa purpurea, both with and without endophytic fungi, and to establish a parasitic system. In this study, endophytic fungal infection was found to increase the dry weight of the leaf, stem, and leaf sheath, as well as the plant height, root length, tiller number, aboveground biomass, and underground biomass of S. purpurea under root hemiparasitic stress. Meanwhile, the 13C allocation of the leaf sheaths and roots of S. purpurea increased as the density of P. kansuensis increased, while the 13C allocation of the leaf sheaths and roots of E+ S. purpurea was lower than that of E- S. purpurea. The 13C allocation of the stem, leaf sheath, and root of E+ S. purpurea was higher than that of its E- counterpart. Furthermore, the content of photosynthetic 13C and the 13C partition rate of the stems, leaves, roots, and entire plant of S. purpurea and P. kansuensis transferred from S. purpurea increased as the density of P. kansuensis increased. These results will generate new insights into the potential role of symbiotic microorganisms in regulating the interaction between root hemiparasites and their hosts.

Host age affects the performance of the root hemiparasitic plant Rhinanthus alectorolophus.

Interactions between root hemiparasitic plants and their hosts are strongly affected by host identity, but may also depend on the condition of the host. An important determinant of host quality could be host age, as it may influence host size, allocation patterns, responses to infection, and the strength of competition for light between parasite and host. We investigated the effects of host species identity, host age and above-ground separation of hemiparasite and host on the interactions between the hemiparasite Rhinanthus alectorolophus and five host species in a factorial experiment. The host species were planted at six different times, from 10 weeks before the parasite was planted to 4 weeks after. Host age strongly influenced the performance of the parasite, but these effects also varied among host species. Parasites grew largest with hosts planted at the same time or 2 weeks earlier, but their performance strongly declined both with increasing host age and with the time they grew autotrophically. A large part of the variation due to host age but not of that due to host species identity could be related to the negative influence of host size at the likely time of parasite attachment. The low quality of older hosts was not due to light competition, suggesting that effective exploitation of these hosts was prevented by other factors like harder roots, stronger defense against parasite attack or competition for resources taken up by the host roots. Suppression of host growth by the parasites declined with increasing host age. The results indicate that the choice of host age may influence the results of studies on hemiparasites. They also highlight the importance for annual root hemiparasites of attachment in early spring, that is, at a time when their mostly perennial hosts produce fresh roots but are still poorly developed above ground.

Understanding parasitism in Loranthaceae: Insights from plastome and mitogenome of Helicanthes elastica

Loranthaceae is the largest family of the order Santalales and includes root and stem hemiparasites. The parasites are known to exhibit reductions in the genomic features as well as relaxed or intensified selection shifts. In this study, we report plastome and mitogenome sequence of Helicanthes elastica (subtribe Amyeminae, tribe Lorantheae), an endemic, monotypic genus of Western Ghats, India growing on remarkably diverse host range. The length of plastome sequence was 1,28,805 bp while that of mitogenome was 1,65,273 bp. This is the smallest mitogenome from Loranthaceae reported till date. The plastome of Helicanthes exhibited loss of ndh genes (ψndhB), ψinfA, rps15, rps16, rpl32, trnK-UUU, trnG-UCC, trnV-UAC and trnA-UGC while mitogenome exhibited pseudogenized cox2, nad1 and nad4 genes. The comparative study of Loranthaceae plastomes revealed that the pseudogenization or loss of genes was not specific to any genus or tribe and variation was noted in the number of introns of clpP gene in the family. Several photosynthetic genes have undergone relaxed selection supporting lower photosynthetic rates in parasitic plants while some respiratory genes exhibited intensified selection supporting the idea of host-parasite arm race in Loranthaceae. The plastome gene content was found conserved in root hemiparasites compared to stem hemiparasites. The atp1 gene of mitogenome was chimeric and part of it exhibited similarities with Lamiales members. The phylogenetic analysis based on plastid genes placed Helicanthes sister to the members of subtribe Dendrophthoinae.

Performance of a parasitic plant and its effects on hosts depends on the interactions between parasite seed family and host species.

Root hemiparasitic plants act as keystone species influencing plant community composition through their differential suppression of host species. Their own performance also strongly depends on interactions with host species. However, little is known about the roles of parasite genetic variation vs. plasticity in these interactions. We grew plants from eight maternal families of the root hemiparasite Rhinanthus alectorolophus with six potential host species (two grasses, two legumes and two forbs) and without a host and measured fitness-related and morphological traits of the parasite, host biomass and overall productivity. Parasite biomass and other traits showed strong plastic variation in response to different host species, but were also affected by parasite maternal family. Parasite seed families responded differently to the hosts, indicating genetic variation that could serve as the basis for adaptation to different host plants. However, there were no negative correlations in the performance of families across different hosts, indicating that R. alectorolophus has plastic generalist genotypes and is not constrained in its use of different host species by trade-offs in performance. Parasite effects on host biomass (which may indicate virulence) and total productivity (host + parasite biomass) depended on the specific combination of parasite family and host species. Mean biomass of hosts with a parasite family and mean biomass of that family tended to be negatively correlated, suggesting selection for maximum resource extraction from the hosts. Specialization of generalist root hemiparasites may be restricted by a lack of trade-offs in performance across hosts, together with strong spatial and temporal variation in host species availability. The genetic variation in the effects on different hosts highlights the importance of genetic diversity of hemiparasites for their effects on plant community structure and productivity and for the success of using them to restore grassland diversity.

Patterns of persistence demonstrate the vulnerability of the root hemiparasite Thesium utile A.W.Hill (Santalaceae) to weed control measures

• Herbicides and mechanical control of C. macrocephalum is likely to have neighbourhood effects on Thesium species. • The biocontrol rust on C. macrocephalum had no impact on T. utile survival. • T. utile is not at risk as it has many hosts and C. macrocephalum is a new association. • Hoeing as a control method is detrimental to T. utile survival. A herbicide trial in a Highveld grassland revealed, serendipitously, a positive association between the root hemiparasite Thesium utile and the noxious weed Campuloclinium macrocephalum (pompom weed). The parasite was unable to survive in plots where the weed was selectively removed by hoeing, but persisted and increased in the untreated control. Herbicides were more effective at killing Thesium than suppressing C. macrocephalum. A host-specific rust attacking the foliage of C. macrocephalum had no impact on T. utile survival. Weed control measures against C. macrocephalum are not likely to threaten native Thesium species as they have a large range of host species. These types of interactions should be investigated further in other species to improve our understanding of the ecology of root-parasites.

A Legume Host Benefits More from Arbuscular Mycorrhizal Fungi Than a Grass Host in the Presence of a Root Hemiparasitic Plant.

In nature, most plants parasitized by root hemiparasites are also colonized by mutualistic arbuscular mycorrhizal (AM) fungi, highlighting the prevalence of this tripartite interaction. AM colonization is generally found to improve the growth of parasitized legumes but has little impact on grass hosts parasitized by root hemiparasites, and the underlying mechanisms are still unclear. In this study, we conducted a pot experiment to test the influence of AM fungus (Glomus mosseae) on the growth and photosynthesis of leguminous Trifolium repens and gramineous Elymus nutans in the presence of a root hemiparasitic plant (Pedicularis kansuensis). The results showed that inoculation with AM fungi significantly improved the growth performance of parasitized legumes via enhancing their nutrient status and photosynthetic capacity, even though a larger P. kansuensis parasitized the legume host in the AM treatment. In contrast, AM colonization slightly improved the shoot DW of grass hosts by suppressing haustoria formation and the growth of P. kansuensis. Our results demonstrated that legume hosts benefit more from AM inoculation than grass hosts in the presence of hemiparasitic plants, and set out the various mechanisms. This study provides new clues for parsing the tritrophic interaction of AM fungi, parasitic plants, and host plants.

Presence of N-fixing neighbors increases leaf N and \u03b413C in Castilleja applegatei, a root hemiparasite

Parasitic plants are known for their high transpiration rates and low water use efficiency (WUE), which the N-parasitism hypothesis posits is driven by N limitation. Thus, availability of N-fixing hosts may affect parasite’s WUE and in turn impact the surrounding plant community. Here, I investigate how the availability of an N-fixing host affects the root hemiparasite, Castilleja applegatei, and examines host-mediated effects on community structure and soil moisture. I surveyed plant diversity and percent cover and measured soil moisture in 120 1 × 1 m plots within Sagehen Experimental Forest, CA. Fifty percent of the plots included C. applegatei. In a subset of plots, I measured leaf N, C/N, δ13C, and δ15N in C. applegatei and in one N-fixer (Ceanothus prostratus) and two non-N-fixing plants (Artemisia tridentata and Wyethia mollis). In C. applegatei availability of N-fixing hosts corresponded to a significant increase in leaf %N, a distinct δ15N signature, and an increase in δ13C (which typically signifies an increased WUE). The presence of parasites was associated with a marginally significant decrease in WUE in N-fixing neighbors, but had no effect on the two non-N-fixing species. The presence of parasites did not impact diversity, percent cover, or soil moisture. These results broadly support the N-parasitism hypothesis and indicate that host type can affect parasite’s physiology and therefore have the potential to mediate parasite’s effects in the community; however, community-level impacts were not found here.

Effects of root hemiparasite Escobedia grandiflora (Orobanchaceae) on southern Brazilian grasslands: Diversity, composition, and functional groups

AbstractAimsEscobedia grandiflora is a root hemiparasite from Central and South America, and its orange roots are used as a phytomedicine and food coloring. Since root hemiparasites from South America have not been extensively investigated, here, in the first study conducted on a Latin American root hemiparasite species, we investigated how Escobedia grandiflora affects the structure and diversity of plant communities in four locations in southern Brazil, all belonging to the Atlantic Forest biome. Specifically, we asked if the presence of the hemiparasite would: (a) affect plant species composition; (b) influence the plant diversity; and (c) influence the percentage cover of dominant plant species.LocationSouthern Brazil.MethodsWe conducted a paired‐quadrat, i.e., with and without hemiparasite, observational study in four locations in southern Brazil. For each quadrat, species composition and percentage of the vegetative cover of each species were visually evaluated.ResultsSpecies composition differed between quadrats with and without Escobedia grandiflora. Quadrats with Escobedia grandiflora showed higher species richness, Shannon´s diversity, and Pielou’s evenness. These results varied also among functional groups. Furthermore, the percentage of dominant species decreased in the presence of Escobedia grandiflora.ConclusionsThere is a clear association between the neotropical root hemiparasite Escobedia grandiflora and the grassland plant community structure. Higher plant diversity, dominance reduction, and changes in species composition are associated with the presence of this perennial hemiparasite. These findings were consistent among four grasslands with markedly different physiognomies. However, future manipulative experiments are necessary to fully disentangle the cause–effect relation between higher plant diversity and the presence of Escobedia grandiflora.

Closely related parasitic plants have similar host requirements and related effects on hosts.

The performance of root hemiparasites depends strongly on host species identity, but it remains unknown whether there exist general patterns in the quality of species as hosts for hemiparasites and in their sensitivity to parasitism. In a comparative approach, the model root hemiparasites Rhinanthus minor and R. alectorolophus were grown with 25 host species (grasses, forbs, and legumes) at two nutrient levels. Hosts grown without parasites served as a control. Host species identity strongly influenced parasite biomass and other traits, and both parasites grew better with legumes and grasses than with forbs. The biomass of R. alectorolophus was much higher than that of R. minor with all host plants and R. alectorolophus responded much more strongly to higher nutrient availability than R. minor. The performance of the two species of Rhinanthus with individual hosts was strongly correlated, and it was also correlated with that of R. alectorolophus and the related Odontites vulgaris in previous experiments with many of the same hosts, but only weakly with that of the less closely related Melampyrum arvense. The negative effect of R. minor on host biomass was less strong than that of R. alectorolophus, but stronger relative to its own biomass, suggesting that it is more parasitic. The impact of the two parasites on individual hosts did not depend on nutrient level and was correlated. Several legumes and grasses were tolerant of parasitism. While R. minor slightly reduced mean overall productivity, R. alectorolophus increased it with several species, indicating that the loss of host biomass was more than compensated by that of the parasite. The results show that closely related parasites have similar host requirements and correlated negative effects on individual hosts, but that there are also specific interactions between pairs of parasitic plants and their hosts.

Ecology, Status and Uses of Osyris Quadripartita (African Sandalwood) in Southern Ethiopia: A Comprehensive Review

Osyris quadripartita (Africa sandalwood) is an evergreen root hemiparasite plant and belongs to the Santalaceae family which is most ordinarily referred to as African sandalwood. It’s a culturally and commercially important species that are used for herbal medicine, religious activities, and thus the perfumery refining industry. The species grows 1 m to 7 m tall counting on the soil type, climate, and genetic variation. The tree occurs on rocky ridges and mountain slopes with an altitude between 900 m to 2550 m above sea level. Regarding to geographic distribution species commonly found in the humid highland and semi-arid ecosystem of Ethiopian. The population structure were an inverted J-shape distribution form and therefore the plant habitats were mostly grouped under Acacia-Rhus-Terminalia community types. Regard to yield quality, it's concluded that sandalwood populations vary substantially within the stock and quality of oil which can be produced. In terms of oil stock the root system is superior to shoot system in quality aspects. Therefore, the main review of this paper was to admission the latest Osyris research and its importance and standing in Ethiopia in order that the knowledge are often used as an honest reference resource for researchers, students, conservationist and NGOs working in Ethiopia within the area of oil crops generally and Osyris in specific. Keywords : Osyris quadripartita, Sandalwood, population structure, Oil crop, Ethiopia DOI: 10.7176/JBAH/11-13-02 Publication date: July 31 st 2021

Controlled Transition in a Model of Biomass Dynamics of Root Hemiparasitic Plants

Controlled Transition in a Model of Biomass Dynamics of Root Hemiparasitic Plants

Effectiveness of Imazapyr Coated Hybrids and Selected Striga-tolerant Varieties on <i>S. hermonthica</i> Management and Maize Yield Performance in Western Part of Kenya

<i>Striga hermonthica</i>, an obligate root hemi-parasite, is a massive biological constraint that hinders maize (<i>Zea mays</i> L.) production in western part of Kenya particularly when susceptible varieties are used. Use of Imazapyr resistant hybrids coated with small doses of imazapyr herbicide offers potential for management of <i>Striga hermonthica</i> and increase maize production. A study was conducted to evaluate the effectiveness of Imazapyr Resistant Maize (IRM) and selected striga tolerant varieties on <i>S. hermonthica</i> management and yield of maize. Field trials were conducted during two successive cropping seasons (2018 and 2019) at Alupe Research Station (artificial inoculation), farmer’s field in Rangwe (natural infestation) and Koibatek Agricultural Training College (striga free) in Busia, Homa Bay and Baringo Counties respectively. The genotypes were evaluated in randomized complete block design with three replication. Test materials comprised of two IRM (H528IR, FRC425IR), two striga tolerant (KSTP94, GAF4), five susceptible commercial hybrids (DK8031, H513, DUMA43, DH04, Haraka 101) and two local landraces (<i>Shipindi, Nya Uyoma</i>). All striga and crop data collected were subjected to analysis of variance and means separated using Tukey’s HSD test. Results showed that IRM varieties significantly (P≤0.05) reduced number of emerged striga plants by 56 and 69% compared to the local landraces and commercial hybrids, respectively. Similarly, IRM varieties produced 50.3 and 79.5% higher grain yields compared to striga tolerant (KSTP94 and GAF 4) and susceptible hybrids, respectively under striga infestation. However, the grain yields recorded at Koibatek ATC (striga free) were 67 and 70% higher than at the Rangwe and Alupe sites, respectively. These findings show that use of Imazapyr resistant technology in maize production contributes to improved striga management and enhances maize grain yields. This technology can be integrated with other measures to contain striga in infested areas.