Assessment of Resistance Mechanisms to Fall Armyworm, Spodoptera frugiperda in Tropical Maize Inbred Lines
The fall armyworm (FAW), Spodoptera frugiperda, a pest of maize native to the Americas first reported in West and Central Africa in 2016, severely threatens maize production and food security in Sub-Saharan Africa. Native genetic resistance is one of the best methods of control of insect pests as it is contained in the seed making it more amenable for use by farmers compared to other interventions and it is also compatible with other integrated pest management (IPM) options. An intensive screening against FAW was carried out by artificial infestation in greenhouse conditions in Kenya between 2017 and 2018 on about 3000 inbred lines available in the germplasm collection of the International Maize and Wheat Improvement Center (CIMMYT). Among these lines, only four showed to be resistant to FAW, but the mechanisms of resistance are not yet known. The objective of this study was to determine the resistance mechanisms specifically non-preference and antibiosis to S. frugiperda in these four selected resistant inbred lines. The studies were conducted under laboratory and net house conditions in Kenya from April 2020 to November 2021. Non-preference was assessed estimating the feeding preference by counting the number of FAW neonates found on each leaf portion, silk portion and grain using binary and multiple choice methods under laboratory conditions, while antibiosis was assessed through the relative growth rate (RGR) and developmental time of FAW larvae on leaves, silks and grains under both laboratory and net house conditions. Among the four resistant maize inbred lines tested, two, namely CML71 and CKSBL10008, exhibited the highest level of antibiosis resistance on leaves. Under laboratory conditions, the larval RGR reduced from 13 mg/d on the most susceptible line to 8 mg/d on CML71. CML71 also showed a good non-preference on leaves compared to other tested lines. Only 6% of neonates choose to feed on CML71 whereas more than 10% choose to feed on the other lines (and 15% on the most susceptible) in multiple choice tests. The non-preference for feeding and lower RGR of larvae on CML71 suggest a biochemical involvement resistance to FAW. Through this study, CML71 is revealed as a highly promising line for use in breeding for native genetic resistance to FAW in tropical maize.
Influence of Si in maize plants in Kenyan populations of Spodoptera frugiperda (Lepidoptera: Noctuidae)
The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), native to the Americas, was confirmed in West and Central Africa in 2016 and reported in almost all countries of sub-Saharan Africa in 2017, becoming thereafter one of the major constraints on the production of maize, the main staple food crop in the region. Cereals depend on silicon (Si)-based defences to fight off herbivores. Both FAW strains, namely rice and corn strains, have been found to be present in Kenya. The present study tested the influence of Si on larval survival and relative growth rate according to the FAW strain, using potted maize plants treated with 10 and 20 g of Si. The results showed that plants treated with Si disturbed the larval growth of FAW larvae only from the corn strain but not from the rice strain. Overall, the corn strain performed better on maize as compared to the rice strain regardless of Si treatment, explaining why it has become the most abundant strain in Africa.
Resistance of maize to fall armyworm (Spodoptera frugiperda) in Africa
The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), a maize pest native to the Americas, was first reported in West and Central Africa in 2016, before invading nearly all sub-Saharan Africa (SSA) in 2017. This new pest causes an estimated $9.4 billion in annual maize yield losses of maize and severely threatens food security in SSA. Faced with this threat, several means of control have been launched by several national and international agricultural research institutions. In the context of the search for rapid solutions, other than the use of synthetic pesticides, the first work undertaken consisted in using silica, a known inducer of plant resistance to biotic and abiotic stresses. A greenhouse study showed that an increase in the silica content of the plant disturbed the development of the larvae of one of the two African populations of FAW. In parallel, a strategy to control FAW in Africa by using host plant resistance from tropical maize germplasm was developed. In this context, an intensive screening against FAW was conducted by artificial infestation in the greenhouse in Kenya between 2017 and 2018 on about 3000 maize lines available in the germplasm collection of the International Maize and Wheat Improvement Center (CIMMYT). Among these lines, four (CKSBL10008, CML71, CML125, and CML370) were found to be resistant to FAW. However, information on the heredity, mechanisms and chemical basis of resistance of these lines was not known. This thesis showed that: 1) for heredity of resistance, heterosis values indicated an increase in resistance of hybrids over the average of inbred line parents. General (GCA) and specific (SCA) combining ability as well as reciprocal were a highly significant source of variation for the inheritance of resistance. CML71 and CKSBL10008 proved to be the best general combiners based on GCA effects for leaf feeding damage. Non-additive genetic effects were highly source of variation for the inheritance of resistance for FAW larval survival, suggesting that heterosis breeding would be the best strategy for improving that resistance trait in the two FAW-resistant inbred lines CML71 and CKSBL10008. 2) Regarding the mechanisms of resistance, CML71 and CKSBL10008 showed the highest level of resistance by antibiosis on leaves due to the low relative growth rates (RGR) of larvae. These two lines were also found to be less preferred by CLA caterpillars due to a lower proportion of larvae found on leaf portions of these genotypes. The non-preference for feeding and low RGR of larvae on these lines suggest biochemical resistance to FAW. 3) Metabolomic analysis revealed that CML71 and CKSBL10008 possess specific metabolites that are absent or less abundant in susceptible lines. From this study, at least 11 metabolites, whose effects against crop pests and diseases have been reported in the literature, were found to be good candidates to explain the resistance to FAW, such as non-protein amino acids like GABA. This thesis reveals that CML71 and CKSBL10008 are very promising lines for breeding native genetic resistance to FAW in tropical maize in SSA.
...Mitigating the impact of the invasive fall armyworm: evidence from South Asian farmers and policy recommendations
In South Asia, the fall armyworm (Spodoptera frugiperda) is an invasive pest. The current research examines the current farming management practices and documents farmers' opinions of fall armyworm in India, Pakistan, Sri Lanka, and Nepal. To assess current agricultural practices, identification of the fall armyworm and its damage, management, capacity-building initiatives, and support from government and non-government extension services, a structured survey of 526 farmers was carried out. The findings indicated that the majority of farmers reported extremely high to moderate fall armyworm damage, and that both the damage and spread grew over time. Chemical pesticides remained the most used technique, despite farmers employing a variety of fall armyworm management practices. While services from government and non-government offices were scarce, farmers learned about the pest and its identification from their fellow farmers and personal experiences. Consequently, a creative extension strategy is required, one that emphasizes the promotion of digital technologies. The management of fall armyworm similarly requires the evaluation and promotion of innovative technologies as a component of integrated pest management (IPM) methods.
...Defining an ‘Invasive species’
Hi all,
I am researching invasive species globally that exhibit the buzz-pollination syndrome. I have used the CABI Invasive Species Compendium Open Data Repository (CABI 2022) to generate a report of invasive angiosperms listed on the CABI Horizon Scanning Tool (using the filters (1) datasheet type: “invasive species”, and (2) sub-phylum: “Angiospermae”. ).
I need to know how CABI has defined an 'invasive' plant as I see these are not all alien invasive plants on the list.
If anyone can point me in the right direction I would be very grateful!
Thanks
...
Special Edition of FAW – Journal of Economic Entomology
Checkout these papers that were just published as a Special Edition in the Journal of Economic Entomology. All papers are free to downlead.
LINK:
https://academic.oup.com/jee/pages/world-scale-ecology-and-management-of-fall-armyworm
...
Want to eggs of spodoptera frugiperda
I am from India, working on spodoptera frugiperda for doctoratal study, i want to eggs of spodoptera frugiperda.
...Spodoptera frugiperda egg mass scale thickness modulates Trichogramma parasitoid performance
The fall armyworm (FAW) Spodoptera frugiperda (Smith) is a major agricultural pest in Americas, Africa and Asia. Egg masses are covered with scale layers and the various scale layer thicknesses of these masses can affect parasitoids efficiency. The present study aimed to determine dynamics of the scale thickness on egg masses and its effect on Trichogramma parasitoid performance. The scale thickness ranged from 0μm to 400 μm and can be graded in three levels. Level I was the naked egg masses without or covered with a thin scale, and the thickness was below 80 μm. Level II was medium covered, with scales where 20%–80% eggs could be seen; the thickness was between 80 μm to 180 μm. Level III was fully-covered with scales and the thickness was above 180 μm (up to 400 μm). The egg mass scale thickness decreased with increasing age of egg laying FAW females; the proportion at level I increased during female aging, while proportion of levels II and III decreased during oviposition period. During FAW female lifetime, the level I showed the highest proportion (51.9%) while the level III showed the lowest (9.9%). The parasitism rate of FAW eggs by Trichogramma dendrolimi varied according to scale thickness, with higher parasitism on eggs and egg masses at level I (31.6%, 78.3%, respectively) and lowest parasitism on level III (eggs: 1.9%; egg masses: 23.1%). We documented factors modulating parasitism effectiveness on FAW and we suggested that timely parasitoid releases targeting egg masses at Level I scale thickness could enable maximizing biocontrol service provided by Trichogramma on FAW.
...Reproductive potential of fall armyworm Spodoptera frugiperda (J.E. Smith) and effects of feeding on diverse maize genotypes under artificial infestation
Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) has become a major threat to maize production in Africa. In this study, six maize genotypes were assessed for their resistance to FAW under artificial infestation in both laboratory and net house conditions. These included two FAW-tolerant hybrids (CKHFAW180294 and CKH191221), two commercial hybrids (WE2115 and CKH10717), and two open-pollinated varieties (ZM523 and KDV4). Larval development time and reproductive potential were assessed on maize leaves in the laboratory and a life table for FAW was constructed. The maize genotypes were also artificially infested with three FAW neonates at two phenological stages (V5 and V7) and reproductive stage (R1) in the net house. Leaf and ear damage scores were recorded on a scale of 1–9. Larval development time varied significantly between maize genotypes with the highest on CKH191221 (16.4 days) and the lowest on KDV4 (13.7 days). The intrinsic rate of natural increase for life tables varied from 0.24 on CKH191221 to 0.41 on KDV4. Mean generation time of FAW ranged from 17.6 to 22.8 days on KDV4 and CKH191221, respectively. Foliar damage was the lowest on CKH191221, and the highest on KDV4 at V7 infestation stage in week 1. CKH191221 had the lowest ear damage score, whereas ZM523 had the highest scores at V5 infestation stage. The highest and lowest yield reductions were observed on ZM523 (64%) at V7 infestation stage and CKHFAW180294 (6%) at R1 infestation stage, respectively. The results indicated the potential for developing tropical mid-altitude maize germplasm with native genetic resistance to FAW.
...HALOPHILA STIPULACEA (HYDROCHARITACEAE) EN LA LAGUNA DE YAPASCUA, PARQUE NACIONAL SAN ESTEBAN, CARABOBO, VENEZUELA Halophila stipulacea (Hydrocharitaceae) in Laguna de Yapascua, San Esteban National Park, Carabobo, Venezuela
ABSTRACT
The species Halophila stipulacea, considered invasive on the coasts of the
Caribbean, was reported for the first time in Venezuela in 2014, in Vargas state.
In this study, the distribution of this species in the country is extended to the coast of Carabobo state. Sampling was conducted in a seagrass bed in Laguna Yapascua
(San Esteban National Park). The vegetation cover and biomass were estimated,
following the CARICOMP protocol. The seagrass H. stipulacea was distributed to
the deep and inner zone of the lagoon, with an average biomass of 40,62 ±
28,43g/m2
and coverage between 40-100%. These results show the expansion of
this species towards the western coast of Venezuela, being necessary to evaluate
the consequences on other species of seagrass and their associated community.
Key words: Caribbean, invasive species, Halophila stipulacea, seagrass,
Venezuela, Yapascua
RESUMEN
La especie Halophila stipulacea, considerada invasora en las costas del
Caribe, fue reportada por primera vez en Venezuela en el año 2014, en el estado
Vargas. En este estudio, se amplía la distribución de esta especie en el país hasta
la costa del estado Carabobo. Los muestreos se realizaron en una pradera de
fanerógamas en la Laguna Yapascua (Parque Nacional San Esteban). Se estimó la
cobertura y la biomasa de la vegetación, siguiendo el protocolo CARICOMP. La
especie H. stipulacea se distribuyó hacia la zona más profunda e interna de la
laguna, con una biomasa promedio de 40,62 ± 28,43g/m2
y coberturas entre 40-
100%. Estos resultados muestran la expansión de esta especie hacia la costa
occidental venezolana, siendo necesario evaluar las consecuencias sobre otras
especies de fanerógamas y las comunidades asociadas.
Palabras clave: Caribe, especie invasora, fanerógamas, Halophila stipulacea,
Venezuela, Yapascua
