Gregory Allan Forbes

Gregory Allan Forbes
International Potato Center

PhD

About

180
Publications
75,439
Reads
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4,555
Citations
Citations since 2016
35 Research Items
2381 Citations
20162017201820192020202120220100200300400
20162017201820192020202120220100200300400
20162017201820192020202120220100200300400
20162017201820192020202120220100200300400
Additional affiliations
December 1988 - present
International Potato Center
Position
  • Senior Researcher

Publications

Publications (180)
Article
Full-text available
Policymakers and donors often need to identify the locations where technologies are most likely to have important effects, to increase the benefits from agricultural development or extension efforts. Higher-quality information may help to target the high-benefit locations, but often actions are needed with limited information. The value of informat...
Article
Full-text available
Potato late blight (LB), caused by the oomycete, Phytophthora infestans, continues to be a major constraint of potato in the Andean region and worldwide. Farmers perception regarding potato production with particular emphasis on management practices for LB was surveyed in two communities in the Peruvian highlands using a questionnaire with 25 quest...
Article
Policymakers and donors often need to identify the locations where technologies are most likely to have important effects, to increase the benefits from agricultural development or extension efforts. Higher-quality information may help to target the high-benefit locations, but often actions are needed with limited information. The value of informat...
Article
Full-text available
CONTEXT Potato is an essential food staple and a critical crop for rural livelihoods in the Republic of Georgia, where many phytosanitary risks threaten production. OBJECTIVE The objectives of this study were, first, to characterize the current seed and ware potato transaction network, value chain, varietal adoption, and phytosanitary risks for Ge...
Article
Full-text available
The geographic pattern of cropland is an important risk factor for invasion and saturation by crop-specific pathogens and arthropods. Understanding cropland networks supports smart pest sampling and mitigation strategies. We evaluate global networks of cropland connectivity for key vegetatively propagated crops (banana and plantain, cassava, potato...
Article
Full-text available
Many decision support systems (DSS) have been developed to manage potato late blight caused by Phytophthora infestans, but most of these require sophisticated equipment and are not realistic alternatives for small-scale farmers in low-income countries. This research evaluates a simple, hand-held decision support tool (HH-DST) consisting of a disk w...
Chapter
Full-text available
Good quality seed is almost universally considered a requirement for high productivity in all potato production systems. Much of the yield gap currently constraining productivity in low-income countries is attributed to the poor quality of seed. Potato seed sector development is thus a major concern of governments, researchers, development agencies...
Poster
Full-text available
A rapidly changing Phytophthora infestans population in eastern Africa expected to be avirulent on a 3R biotech potato
Data
Figure S1 Gene expression of the RB, Rpi‐blb2 and Rpi‐vnt1.1 gene in the triple R gene transgenic event Vic.1 from the variety ‘Victoria’ relative to the expression 1 day before infection (dbi) by P. infestans strain POX067. Figure S2 Field layout of the confined field trials. Table S1 List of primers and amplification conditions used to characte...
Preprint
Full-text available
Host resistance is a realistic approach to manage potato late blight (LB), caused by the oomycete pathogen Phytophthora infestans. Available host resistance in east Africa is barely known due to the high proportion of susceptible cultivars grown. We thus quantified host resistance of ten potato cultivars widely grown in southwestern Uganda (Victori...
Preprint
Full-text available
Assessing durability of R-gene mediated resistance to late blight (LB) is a challenge. We investigated the Phytophthora infestans population in Kenya, Uganda, Rwanda and Burundi for the expression of three effector-genes, Avrblb1, Avrblb2 and Avrvnt1, corresponding to and recognized by RB/Rpi-blb1, Rpi-blb2 and Rpi-vnt1.1 resistance-genes respectiv...
Article
Full-text available
The displacement in east Africa of the US‐1 clonal lineage of Phytophthora infestans by 2_A1 clonal lineage has been very rapid. In this study, we tested the hypothesis that dominance of 2_A1 could be due, at least in part, to the increased aggressiveness of 2_A1 over US‐1 using both a detached leaf assay (DLA) and a tuber slice assay. The assays w...
Article
Full-text available
Considered responsible for one million deaths in Ireland and widespread famine in the European continent during the 1840s, late blight, caused by Phytophthora infestans, remains the most devastating disease of potato (Solanum tuberosum L.) with about 15‐30% annual yield loss in sub‐Saharan Africa, affecting mainly smallholder farmers. We show here...
Article
An unknown Phytophthora species was discovered in the Central Peruvian Andes on blighted foliage of the native South American plant species Urera lacineata. Urera is a genus of native flowering shrubs in the nettle family Urticaceae. This new taxon Phytophthora urerae sp. nov. is herewith formally described based on extensive morphological analysis...
Article
Full-text available
Strains of Phytophthora infestans, the pathogen causing late blight of potato and tomato, are thought to be moved around the world through infected planting material. Since its first appearance in 1941, late blight has caused important losses to potato production in the eastern-Africa region (EAR). In the current study, the genetic structure of the...
Preprint
Full-text available
Identifying the locations and settings where technologies are most likely to have important effects can make the most of development or extension efforts. In the context of development and applied ecology, decisions must often be made by policy makers and donors about where to implement projects designed to improve management. Implementation in som...
Article
Late blight, caused by the oomycete Phytophthora infestans is a threat to potato cropping systems worldwide. In the Ecuadorian Andes, in spite of a high late blight incidence in foliage, tuber blight is rare. In this work, we evaluated the hypothesis that Ecuadorian Andean soils are naturally suppressive to P. infestans tuber infection. Soils from...
Article
Full-text available
The Avr avirulence gene of Phytophthora infestans and R gene of the potato are the genetic components of the gene-for-gene interaction resulting in host plant resistance. This effector-triggered immunity has been recently exploited to generate extreme resistance to late blight in potato by genetic engineering. The choice of the R genes, their numbe...
Technical Report
Full-text available
The requirements of formal systems of potato seed production are impractical in the Andes and almost impossible to put in place due to the low incidence of virus permitted in the marketed seed and strict formal procedures. A recent study that analyzed the results of research done 30 years ago refutes the belief that all progeny tubers from plants g...
Article
Resistance genes are a major tool for managing crop diseases. The networks of crop breeders who exchange resistance genes and deploy them in varieties help to determine the global landscape of resistance and epidemics, an important system for maintaining food security. These networks function as a complex adaptive system, with associated strengths...
Article
Full-text available
Seed systems have an important role in the distribution of high-quality seed and improved varieties. The structure of seed networks also helps to determine the epidemiological risk for seedborne disease. We present a new approach for evaluating the epidemiological role of nodes in seed networks, and apply it to a regional potato farmer consortium (...
Preprint
Seed systems have an important role in the distribution of high quality seed and improved varieties. The structure of seed networks also helps to determine the epidemiological risk for seedborne disease. We present a new method for evaluating the epidemiological role of nodes in seed networks, and apply it to a regional potato farmer consortium (CO...
Research
Full-text available
Phytophthora infestans (Pi) is the causative pathogen for the late blight disease in potato. It remains one of the most devastating plant pathogens worldwide amidst a shift in its population with changes that influence disease management. East-Africa has recently reported a change in its Pi population with a fitter clonal genotype, KE-1, discovered...
Article
Full-text available
Pathogen buildup in vegetative planting material, termed seed degeneration, is a major problem in many low-income countries. When smallholder farmers use seed produced on-farm or acquired outside certified programs, it is often infected. We introduce a risk assessment framework for seed degeneration, evaluating the relative performance of individua...
Preprint
Full-text available
Resistance genes are a major tool for managing crop diseases. The crop breeder networks that exchange resistance genes and deploy them in varieties help to determine the global landscape of resistance and epidemics, an important system for maintaining food security. These networks function as a complex adaptive system, with associated strengths and...
Preprint
Full-text available
Low potato productivity in Ecuador is partly attributed to the use of low quality seed tubers. However, seed health quality in Ecuador, and its interaction with altitude and yield has been poorly investigated. We surveyed 11 farmers’ fields in Ecuador in 2010 to determine incidence and severity of pathogens and pests affecting foliage and seed tube...
Article
Full-text available
The common assumption in potato virus epidemiology is that all daughter tubers produced by plants coming from infected mother tubers (secondary infection) will become infected via systemic translocation of the virus during growth. We hypothesize that depending on the prevalent environmental conditions, only a portion of the daughter tubers of a pla...
Preprint
Full-text available
Pathogen build-up in vegetative planting material, termed seed degeneration, is a major problem in many low-income countries. When smallholder farmers use seed produced on-farm or acquired outside certified programs, it is often infected. We introduce a risk assessment framework for seed degeneration, evaluating the relative performance of individu...
Article
Full-text available
Mitochondrial DNA (mtDNA) haplotypes were determined using restriction fragment length polymorphism (RFLP) for P. infestans sampled from 513 foliar lesions of late blight found on potato and tomato in different regions of Ethiopia. Among the four reported mitochondrial haplotypes of Phytophthora infestans, Ia, Ib and IIb were detected in 93 % of th...
Article
The major pests and diseases were identified and quantified on thirteen potato landraces and three bred varieties cultivated in Peru. Late blight (Phytophthora infestans) was the primary biotic constraint affecting plants before flowering with an average severity of 24%. No other pathogens caused severe foliar disease, but black scurf (Rhizoctonia...
Article
Full-text available
The Rpi-blb2 gene (R gene) from the Mexican wild potato species, Solanum bulbocastanum, was introduced into the potato variety Desiree by agro-infection in order to confer resistance to late blight which is still the most important disease of the potato worldwide. A total of 148 putative transgenic events was obtained by selection based on hygromyc...
Article
Tree tomato, Solanum betaceum, is an Andean fruit crop previously shown to be attacked by Phytopthora andina in Ecuador and Colombia. Blight like symptoms were discovered on tree tomato plants in the central highlands of Peru at 2003 and shown to be caused by P. andina. Isolates of P. andina collected from three different plantations in Peru during...
Conference Paper
Full-text available
Potato production in sub-Saharan Africa (SSA) has more than doubled since 1994, with 70% of that growth concentrated in Eastern Africa. Despite these gains, potato yields of small-scale farmers in the region fall far short of their potential due to various factors including biotic and abiotic constraints, inadequate supplies of high-quality seed an...
Article
Phytopthora infestans (Mont.) de Bary the pathogen responsible for causing late blight in potato and tomato is a rapidly evolving and highly adaptable pathogen. Following the appearance of a new clonal genotype in Kenya (KE-1 lineage) in 2007, there was a need to document possible displacement of the older US-1 genotype by the newer lineage. Sample...
Article
Full-text available
Seed potato degeneration, the reduction in yield or quality caused by an accumulation of pathogens and pests in planting material due to successive cycles of vegetative propagation, has been a long-standing production challenge for potato growers around the world. In developed countries this problem has been overcome by general access to and freque...
Article
Full-text available
One of the most efficient options for the control of late blight disease in potato (Solanum tuberosum) is the development of resistant varieties to Phytophthora infestans mediated by the direct transfer of resistance (R) genes through genetic engineering. In the present work, we used Solanum bulbocastanum RB gene to confers broad spectrum resistanc...
Article
Full-text available
Late Blight Resistance as a control tool in developing countries Potato late blight may be controlled by several approaches including host resistance. Unfortunately, efforts to date to use host resistance have led to limited successes and many failures as pathogen populations have rapidly evolved to overcome resistance or durably resistant cultivar...
Article
Full-text available
The wild and cultivated species of potato have been utilized in potato breeding to good effect but only a very small sample of the available biodiversity has been exploited. In total, 468 accessions of wild and cultivated species of potato were assessed for resistance to the oomycete pathogen Phytophthora infestans using greenhouse assays. Wide phe...
Article
Full-text available
Significance The potato late blight pathogen was introduced to Europe in the 1840s and caused the devastating loss of a staple crop, resulting in the Irish potato famine and subsequent diaspora. Research on this disease has engendered much debate, which in recent years has focused on whether the geographic origin of the pathogen is South America or...
Technical Report
Full-text available
In 2013, the Research Program on Roots, Tubers, and Banana (CRP-RTB) of the Consultative Group on International Agricultural Research (CGIAR) approved the initial 3-year project on “Management of RTB-critical pests and diseases under changing climates, through risk assessment, surveillance and modeling”. The regional planning workshop, held in Kaba...
Chapter
Full-text available
Potato (Solanum spp.) ranks third in importance as a single food crop worldwide. Late blight, caused by Phytophthora infestans, is considered to be the most important single biotic constraint of potato, but degeneration of vegetative planting material, caused primarily by a complex of viruses, potentially causes even greater yield losses. Arthropod...
Article
Weather affects the severity of many plant diseases, and climate change is likely to alter patterns of crop disease severity. Evaluating possible future patterns can help focus crop breeding and disease management research. We examined the global effect of climate change on potato late blight, the disease that caused the Irish potato famine and sti...
Article
Full-text available
The Oomycete Phytophthora infestans (Mont.) de Bary, the causal agent of the disease known as late blight, is primarily responsible for the decreased in production performance and potato crops worldwide. The integration of the complete R genes sequences in the potato genome using Agro-transformation appears an alternative to be considered in the fi...
Article
Full-text available
Potato genotypes from a breeding population adapted to tropical highlands were analyzed for the stability of the late blight resistance and also for marker-phenotype association. We harmonized the historical evaluation data consisting of observations spanning six years from two field sites utilizing a resistance scale (sAUDPC) constructed by compar...
Chapter
Climate has an important effect on plant disease and the probability of plant pathogen invasions, through effects on hosts and pathogen vectors as well as on the pathogens themselves. Aerially dispersed pathogens are an important group of plant pathogens, and their dispersal and invasion may be modified by changes in wind patterns. Pathogens vector...
Article
Full-text available
The Oomycete Phytophthora infestans (Mont.) de Bary, the causal agent of the disease known as late blight, is primarily responsible for the decreased in production performance and potato crops worldwide. The integration of the complete R genes sequences in the potato genome using Agro-transformation appears an alternative to be considered in the fi...
Chapter
Full-text available
Full PDF available here: http://www.cides.edu.bo/webcides/images/pdf/Cambio_climatico_en_el_altiplano_boliviano.pdf
Article
Full-text available
Abstract An experiment was conducted to determine the host resistance of potato against Phytophthora infestans for twenty-five potato genotypes in 2010 and 2011 at Khumaltar, Lalitpur, Nepal using four assays: three for foliage resistance (field, whole-plant and detached leaf) and one for tuber resistance (tuber slice). An isolate of P. infestans c...
Chapter
Full-text available
This book begins with an account of the early history of Phytophthora research and the tumultuous events setting the genus in motion. In keeping with its controversial inception, the chapter on taxonomy and phylogeny makes a compelling case that our current notion of Phytophthora as a genus is illusory. This chapter sets the stage for the importanc...
Article
Full-text available
Potato late blight may be controlled by several approaches including host resistance. Unfortunately, efforts to date to use host resistance have led to limited successes and many failures as pathogen populations have rapidly evolved to overcome resistance or durably resistant varieties have had limited adoption. Several problems hinder diffusion of...
Poster
Full-text available
The cultivated potato, Solanum tuberosum is affected by a variety of diseases with late blight (LB) caused by Phytophthora infestans being the most severe. The disease is mostly controlled by the application of large quantities of fungicides, which represent a financial burden on farmers in developing countries and pose risks to both human health a...
Article
Full-text available
Twenty phosphonate products found in the agrochemical market in Ecuador and Peru were evaluated in bioassays for the control of foliar potato late blight, caused by Phytophthora infestans. Eight phosphonate products were evaluated in 16 field experiments done in Peru, Ecuador, Kenya, and Nepal. A meta-analysis across locations involving 71 combinat...