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This study aimed at estimating carbon footprint (CF) and assessing mitigation options for selected tropical crops using excel-based models, parameterized with data collected through closed-ended questions questionnaires, combined with a reference trial (RT). Most of the estimates using structured interviews were similar to those measured in the RT and the literature. Total average emission intensities ranged from 24 to 290 kg CO2eq·Mg−1, where the extreme values corresponded to cassava in the RT (24 kg CO2eq·Mg−1) and maize in interviewed farmers in Barranca province (290 kg CO2eq·Mg−1). Overall, fertilizer production and application contributed to 77% of total greenhouse gas (GHG). Transportation generated emissions comparable to field estimates. Farm emissions can be reduced in 17 to 27% with incorporation of mitigation practices. The methodology used in this study constitute a useful and easily applicable tool to assess ex-ante the impact of policies and decisions on CF under farm conditions. It can also be used by different stakeholders for different purposes; including but not limited to: label products offered in the market with GHG emission estimates, make decisions to regulate the emissions in the agricultural sector, and to enable farmers to negotiate prices and incentives for environmental preservation with quantitative information. Keywords: Peru, Emissions, Maize, Sweet potato, Cassava, Fertilizers

Potatoes&mdash, a global food security and staple crop&mdash, is threatened by dry spells in drought-prone areas. The use of physiological thresholds to save water while maintaining a reasonable tuber yield has been proposed, but their effects on physiological performances and usefulness under different irrigation methods are yet to be evaluated. In this study, photosynthetic traits were monitored to assess the effect of water restriction and rewatering under drip (DI) and furrow (FI) irrigations. The treatments consisted of two maximum light-saturated stomatal conductance (g s _ m a x ) irrigation thresholds (T2: 0.15 and T3: 0.05 mol H 2O m &minus, 2 s &minus, 1 ) compared with a fully irrigated control (g s _ m a x &gt, 0.3 mol H 2O m &minus, 1 ). DI used less water than FI but promoted early senescence and low percentage of maximum assimilation rate (PMA) at late developmental stages. FI caused no yield penalization in T2 and higher recovery of carbon isotope discrimination and PMA than DI. It is suggested that moderate water quantities of early and frequently water pulses in the irrigation, promote short-term water stress memory improvement, senescence delay and more capability of recovery at late stages.

Low radiation is one of the most important factors which limits potential yield in potato. Under humid conditions, the dominance of diffuse radiation not only imposes challenges for radiation use efficiency in crops but also limits the water status surveillance through non-invasive methods like infrared radiometry. This study was carried out in the humid desert of the Peruvian central coast with the aim to relate maximum stomatal conductance (gs_max, an important water status indicator) with leaf and air temperature (dT) and crop water stress index (CWSI). In a potted trial, gs_max vs. dT were compared along the day in well-irrigated (field capacity) and water restricted (half field capacity) plants. In an additional field experiment, CWSI was validated by testing two irrigation timing treatments with pre-established gs_max threshold (0.15 [T1] and 0.50 [T2] mol H2O m−2 s−1) against a control (frequently irrigated). An acute stomatal closure sensitivity was detected which drove a gs_max fall (gs↓) near the solar noon. The intense stomatal closure caused a dT rise which showed positive higher values (> 2 °C) after gs↓. The significant yield reduction of T1 in relation to the control (− 38.2 ± 10.7%) highlighted that gs_max values > 0.15 must be used to warrant a high potato yield. These findings support the use of CWSI values ≤ 0.3–0.4 as thresholds for an appropriate irrigation in potatoes with assessments taken at around 15:00 hours, time in which plants have accumulated enough radiation allowing an appropriate detection of thermal emission under humid conditions.

According to potato experts from ten Sub-Saharan Africa (SSA) countries working together in a community of practice (CoP) over a 3-years period, potato farmers across SSA can increase their current annual production of 10.8 million metric tons by 140% if they had access to high quality seed along with improved management practices. This paper describes this innovative new methodology tested on potato for the first time, combining modelling and a comprehensive online survey through a CoP. The intent was to overcome the paucity of experimental information required for crop modelling. Researchers, whose data contributed to estimating model parameters, participated in the study using Solanum, a crop model developed by the International Potato Center (CIP). The first finding was that model parameters estimated through participatory modelling using experts’ knowledge were good approximations of those obtained experimentally. The estimated yield gap was 58 Mg ha-1, of which 35 corresponded to a research gap (potential yield minus research yield) and 24 to farmers’ gap (research yield minus farmer’s yield). Over a 6-month period, SurveyMonkey, a Web-based platform was used to assess yield gap drivers. The survey revealed that poor quality seed and bacterial wilt were the main yield gap drivers as perceived by survey respondents.

Partial root-zone drying (PRD) is an irrigation technique which consists of alternating the water supply from one furrow to another, and keeping the other one dry during the weekly alternation period. Studies assessing PRD in potato have reported a 30-50% of water savings with no tuber yield reductions and an increase of antioxidant concentrations and marketable tubers. In this study, we adapted the PRD technique to rural Ethiopian conditions and compared it against the customary (C) irrigation practiced by local farmers. Two PRD alternatives were evaluated; with (PRDs) and without (PRDw) locally made flexible-hose siphons. Only PRDs showed no significant differences in total (35.8±1.6 t ha-1) and marketable (34.2±1.6 t ha-1) tuber yield when compared with customary irrigation (39.4±1.3 and 37.6±1.2 t ha-1 corresponding to total and marketable yield, respectively). The PRDw was more water restricted, showing significantly lower total (29.7±1.1 t ha-1) and marketable (27.6±1.2 t ha-1) yields. PRDs had the benefit of a better control of applied water allowing a saving of 50% of the irrigation water without negatively affecting yield. The use of the siphons PRD technique provides options for saving scarce water and reaching out to many smallholder farmers who are in serious need of irrigation water in the Blue Nile river basin.

The definition of irrigation schedules depends on the understanding of the response of key plant traits to different water restriction characteristics with the aim to avoid physiological impairment. In this study, different timings (at tuber initiation and bulking) and intensities (four soil moisture levels) of water restriction were tested in the potato crop. The temporal patterns of mid-morning or maximum, light saturated stomatal conductance ( g s_max ), recovery of net photosynthesis ( A recovery ), stem water potential (Ψ stem ), carbon isotope discrimination in tubers (Δ tuber ), plant water concentration ( PWC ), photochemical reflectance index ( PRI ) and crop water stress index ( CWSI ) were analyzed. Early-severe water restriction caused a drastic yield reduction, with low recovery of physiological responses ( g s_max , Δ tuber , Ψ stem , CWSI , A recovery ) after 15 days of post-restriction irrigation and even a continued reduction of some of them ( PWC , PRI ). It also caused a prolonged g s_max reduction below 0.05 mol H 2 O m −2 s −1 (≈ 5 μmol CO 2 m −2 s −1 of net photosynthesis) suggesting that this value defines a physiological severity threshold in potato, under which a metabolic impairment occurs. CWSI and PRI showed a close linear (R 2 = 0.76) and no linear (natural logarithm function, R 2 = 0.67) relationship with g s_max respectively. In cloudless dry environments, irrigation schedules in potato should aim to avoiding CWSI values higher than 0.4, especially until before of maximum canopy cover establishment. A close relationship between A recovery at maximum stress moment and yield reduction was found. The strong relationship between the measured traits (except PWC and Ψ stem ) and final yield at maximum stress moment found in the present study warrants further research on drought phenotyping immediately before post-restriction irrigation or when the defined severity threshold in potato is reached.

Access to Water and Nitrogen (N) are key challenges in potato crop management that could be optimized through understanding related agronomic and physiological traits. The responses to water deficit and two levels of nitrogen (0 and 200 kg N.ha-1) were assessed here for agronomic and physiological traits for potato genotypes UNICA, Achirana-INTA, and CIP397077.16, chosen for their short vegetative period (90–-110 days) and tolerance to water deficit. Nitrogen Use Efficiency (NUE) was greatly reduced in all genotypes under drought, even dropping to nearly zero. Despite this, the tuber yield and total biomass reduction of around 50 % for all genotypes could be alleviated with N application. Normalized Difference Vegetation Index (NDVI), chlorophyll content (SPAD), and Canopy cover (CC) were found to be good indicators for predicting nitrogen deficits and detecting early stress by drought. Overall, each genotype had different strategies to manage N and cope with drought stress. UNICA was the most efficient genotype at using the N present in the soil and tolerating drought stress, while Achirana-INTA was most affected by drought in terms of NUE. Based on the results, it is suggested that maximum fertilizer use efficiency can be obtained with low N rates applied under well-watered conditions. Improved NUE and a greater understanding of the physiological response of crops to drought stress and N fertilization will help to reduce fertilizer use, lessening the effects of water contamination and improving input efficiency.

Ten potato genotypes with field resistance to bacterial wilt were evaluated for resistance to five strains of Ralstonia solanacearum belonging to biovars 1, 2A, 2T and 3 (phylotypes I and II) under greenhouse conditions. The plants were inoculated by pouring bacterial suspension into the soil and wilt incidence was recorded weekly. Stems and tubers of symptomless plants were tested for latent infection using post-enrichment NCM-ELISA. The analysis of variance of the percentage of infected plants indicated significant differences among potato genotypes and strains of R.solanacearum. Complete resistance to all tested strains was not observed in any of the potato genotypes. However, CIP 394895.7 was the most resistant genotype, showing hardly any wilting and low level of latent infections. The use of potato varieties with partial resistance like this genotype in combination with crop rotation, healthy seed and sanitation practices could significantly reduce losses due to bacterial wilt.

Drought strongly influences potato (Solanum tuberosum) production and quality. Potato being a drought susceptible crop, the development of varieties with enhanced tolerance to water stress could highly improve productivity in drought prone areas. The objective of this study was to evaluate the ability of several yield based indices to be used in large scale screening for drought tolerance. The experiment included improved varieties, genetic stocks and landraces potatoes grown under drought and irrigated conditions. A group of accessions with high yield under both conditions was identified. Mean productivity (MP), geometric mean productivity (GMP), tolerance (TOL), drought tolerance index (DTI), drought susceptible index (DSI) and yield stability index (YSI) were calculated from tuber yield under drought and irrigated conditions. The relationships between these indices and yield were analyzed. The Fleiss’ Kappa concordance test was used to analyze the correspondence between accessions previously identified as highly productive under both drought and irrigated conditions and accessions with optimal values for the different indices. MP, GMP and DTI allowed identifying genotypes combining high yield potential and high yield under drought within the three subsets of genotypes. Conversely, DSI, YSI and TOL showed low and variable concordance values across subsets, suggesting that their efficiency in screening genotypes highly depends on the nature of the tested genetic material.

El objetivo del estudio fue estimar la huella de carbono (HC) en la produccion mecanizada de maiz, camote y yuca, asi como identificar y proponer opciones de mitigacion en la costa del Peru. Se realizo una encuesta a 100 productores de Barranca y Canete en la region de Lima. Se registraron todas las practicas de produccion y proteccion de cultivos. La estimacion se llevo a cabo con el modelo de simulacion programado en Excel; Cool Farm Tool (CFT). El maiz en Barranca registro la mayor cantidad de labranza y aplicaciones de pesticidas. En ambos lugares, se aplicaron dosis medias a altas de N al maiz, mientras que el camote y yuca solo recibieron dosis altas. Cuando las emisiones de CO 2 por transporte fueron incluidas en los analisis, las fincas que cultivaban yuca en Barranca generaron 267 kg CO 2 eq·t -1 , que fue la mayor HC (132 kg CO 2 eq·t -1 adicionales). Esta adicion fue similar en todos los cultivos. Las principales fuentes de emision de gases de efecto invernadero (GEI) para los tres cultivos fueron la aplicacion (49%) y la produccion (38%) de fertilizantes, seguida del uso de plaguicidas (13%). Las opciones de mitigacion simuladas con el CCAFS-Mitigation Options Tools (CCAFS-MOT) incluyeron el uso de labranza minima, la incorporacion de residuos agricolas, el uso de fertilizantes organicos procesados e inhibidores de nitrificacion. Al incorporar las cuatro opciones de mitigacion se estimaron reducciones de GEI en 42%, 22% y 26% para el maiz, camote y la yuca, respectivamente.

Plant breeders and educators working with the International Potato Center (CIP) needed freely available statistical tools. In response, we created first a set of scripts for specific tasks using the open source statistical software R. Based on this we eventually compiled the R package agricolae as it covered a niche. Here we describe for the first time its main functions in the form of an article. We also review its reception using download statistics, citation data, and feedback from a user survey. We highlight usage in our extended network of collaborators. The package has found applications beyond agriculture in fields like aquaculture, ecology, biodiversity, conservation biology and cancer research. In summary, the package agricolae is a well established statistical toolbox based on R with a broad range of applications in design and analyses of experiments also in the wider biological community .

This paper analyzes some important issues surrounding possible deployment of genetically engineered (GE) insect-resistant potato in Peru, based on a large farmer survey held in Peru in 2003. We found that the formal seed system plays a limited role compared with the informal seed system, especially for smallholder farmers. Although 97% of smallholder farmers would buy seed of an insect-resistant variety, a majority would buy it only once every 2 to 4 years. Survey data show that farmers would be willing to pay a premium of 50% on seed cost for insect resistant varieties. Paying price premiums of 25% to 50%, farmers would still increase their net income, assuming insect resistance is high and pesticide use will be strongly reduced. Of all farmers, 55% indicated preference for insect-resistant potato in varieties other than their current varieties. The survey indicates that smallholder farmers are interested to experiment with new varieties and have a positive perception of improved varieties. Based on these findings, and considering the difficulties implementing existing biosafety regulatory systems such as those in place in the U.S. and E.U., we propose to develop a variety-based segregation system to separate GE from conventionally bred potatoes. In such a system, which would embrace the spread of GE potatoes through informal seed systems, only a limited number of sterile varieties would be introduced that are easily distinguishable from conventional varieties.

Genebanks increasingly use molecular markers for routine characterization of ex-situ collections and farmer managed diversity. The International Potato Center presently uses a SSR marker-kit to create molecular profiles for potato accessions. We identified a need for a compact graphical representation that allows comparative presentation of molecular diversity and accession characteristics - thereby permitting biologists and collection curators to have a simple means to interpret molecular data. Inspired by the ancient Andean qipus we devised a graph that standardizes representation while leaving room for updates of the marker kit and the collection of accessions. The molecular khipu permits combining and annotating a set of SSR loci with allele frequency and allele size distribution information. The design is flexible to incorporate updates on genetic diversity information. Graphical means facilitate reading of allele diversity information. As a compact graphical view it facilitates information storage and exchange. The SSR khipu will be useful to other genebanks and breeders. Software to create graphics in single or batch mode is available as R package ’khipu’.