This study aimed to analyze the seed potato systems in Ethiopia, identify constraints and prioritize improvement options, combining desk research, rapid appraisal and formal surveys, expert elicitation, field observations and local knowledge. In Ethiopia, informal, alternative and formal seed systems co-exist. The informal system, with low quality seed, is dominant. The formal system is too small to contribute significantly to improve that situation. The informal seed system should prioritize improving seed quality by increasing awareness and skills of farmers, improving seed tuber quality of early generations and market access. The alternative and formal seed systems should prioritize improving the production capacity of quality seed by availing new varieties, designing quality control methods and improving farmer's awareness. To improve overall seed potato supply in Ethiopia, experts postulated co-existence and linkage of the three seed systems and development of self-regulation and selfcertification in the informal, alternative and formal cooperative seed potato systems.Resumen Este estudio tuvo el propósito de analizar los sistemas de producción de papa en Etiopia, identificar limitantes, y priorizar opciones de mejorar, mediante la combinación de investigación de escritorio, apreciaciones rápidas y estudios formales, encuestas a expertos, observaciones de campo y conocimiento local. En Etiopia co-existen sistemas de semilla informal, alternativo y formal. Domina el sistema informal, con baja calidad de semilla. El sistema formal es muy pequeño como para contribuir significativamente al mejoramiento de esa situación. El sistema informal de semilla debería tener como prioridad el mejoramiento en la calidad de la semilla mediante el aumento en la atención y habilidades de los productores, mejorando la calidad de la semilla-tubérculo de las generaciones tempranas y el acceso al mercado. Los sistemas alternativo y formal de semilla deberían priorizar el mejoramiento en la capacidad de producción de semilla de calidad, mediante la validación de nuevas variedades, el diseño de métodos de control de calidad, y mejorando la atención del productor. Para mejorar el suministro general de semilla de papa en Etiopia, los expertos postularon la co-existencia y asociación de los tres sistemas de semillas y el desarrollo de autorregulación y autocertificación en los sistemas cooperativos de semilla de papa informal, alternativo y formal.

Artemisinin is a sesquiterpene lactone endoperoxide and an important antimalarial drug produced in Artemisia annua. To unravel the diverse processes determining artemisinin yield in A. annua crops, artemisinin accumulation during the development of individual leaves was studied in two field experiments. During the life cycle of a leaf, artemisinin was always present. Quantities were low at leaf appearance and increased steadily. In leaves studied until after senescence, maximum quantities and concentrations were achieved after the leaf had turned brown. The total quantity of possible artemisinin precursors per leaf (dihydroartemisinic acid and other upstream precursors) was highest early in the leaf cycle when the leaf was still expanding. Dihydroartemisinic acid was more abundant than the other compounds and its quantity declined during leaf development whereas that of artemisinin increased. Dihydroartemisinic acid was not converted directly into artemisinin, because on a per leaf basis the decline in molar quantity of precursors in the earliest formed leaves was not compensated for by a simultaneous increase in artemisinin. Our results suggest that a (putative) intermediate such as dihydroartemisinic acid hydroperoxide temporarily may have accumulated in considerable quantities. The number of mature, capitate trichomes on the adaxial leaf side increased after leaf appearance until the end of leaf expansion, and then decreased, probably due to collapse of trichomes. Artemisinin production thus (also) occurred when trichomes were collapsing. Later formed leaves achieved higher concentrations of artemisinin than earlier formed leaves, because of a higher trichome density and a higher capacity per trichome.

A novel cropping system for potato was tested for two consecutive years under normal Dutch agronomic conditions. Seedlings from two experimental genotypes of hybrid true potato seeds were produced in a greenhouse nursery and transplanted into the field 5 weeks after sowing to assess tuber yield levels and to study effects of hilling on tuber yield and number, tuber size distribution and tuber greening. Field experiments had a split-plot design with hilling treatments as the main plots and genotypes as the sub-plots. Final harvest was at 122 and 132 days after transplanting in 2017 and 2018, respectively. Hybrid seedlings were transplanted into small initial ridges and irrigated straight after planting. Three hilling treatments were applied between transplanting and 100% canopy cover. Treatment ‘zero hilling’ did not receive any additional hilling after transplanting. Treatments ‘double hilling’ and ‘triple hilling’ received two and three additional hilling treatments, respectively. Total tuber yields at final harvest in both years were not affected by the hilling treatments. Yields for the respective genotypes were 26 and 30 Mg/ha in 2017 and 25 and 32 Mg/ha in 2018. Total tuber numbers were only affected by hilling treatments in 2017, where under hilled conditions, plants produced more tubers compared with plants under zero hilling. Plants under zero hilling yielded more tubers in size class > 40 mm compared with triple hilling in 2017. In 2018, no significant effects of hilling on tuber numbers were found, but the trend was similar to that in 2017.

Smallholder farmers in Uganda commonly use seed potato tubers from the informal sector, especially by seed recycling over several generations. Therefore, seed tubers are highly degenerated with viruses and other pathogens, resulting in poor yield and quality of the produce. Over one cycle of multiplication, degeneration management by positive seed selection was found to be efficient in reducing virus diseases compared with the farmers' method of selection. The objective of this study was to assess to what extent positive selection over several seasons can reduce six different virus incidences in seed lots of different starting quality in southwestern Uganda. Multi-seasonal trials were carried out in three locations, with five seed lots from four sources and three cultivars. Detection of viruses was based on DAS-ELISA and Luminex xMAP technology. Analysis was carried out with analysis of variance (ANOVA) on angulartransformed percentages of virus incidence. Results showed fluctuations in some viruses over seasons with lower Potato leafroll virus (PLRV) and Potato virus X (PVX) incidences in lots from positive selection compared with lots from farmers' selection. In contrast, some seed lots were initially highly infected with Potato virus S (PVS) and Potato virus M (PVM) and showed no reduction in virus incidence through positive selection. In general, little infection with Potato virus Y (PVY) and Potato virus A (PVA) was found. Based on these results, it is recommended that smallholder farmers are trained in positive selection to opt for less virus-infected plants and tubers, thus increasing potato production.

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METHODOLOGYTh e study entailed two main steps. First, a so-called Delphi study was conducted to identify and prioritize, among experts and farmers, seed potato management attributes (e.g., sprouting method, fertilizer rates) aff ecting yield and seed quality. Th en, a two-part survey was performed (i) by conducting face-to-face interviews among farmers to collect specifi c demographic and management data, and (ii) by using a so-called conjoint task to elicit farmers' opinions on eff ects of selected management attributes on seed yield and quality.ABSTRACT A low adoption of recommended seed potato (Solanum tuberosum L.) technologies in Ethiopia could be due to a lack of alternative seed potato production methods compatible with farmers' economic and agro-ecological conditions. A conjoint analysis (a technique used to measure relative contribution of product attributes) was conducted to elicit farmers' opinions on management attributes that they believed to aff ect yield and quality of potato. Th e study involved interviewing 324 farmers who grew seed potato in Jeldu and Welmera districts. Th e results showed that management attributes, such as storage method, hoeing combined with hill size, fertilizer rate (FR) and fungicide application (FA) frequency had larger eff ect on seed yield and quality than seed source, seed size, sprouting method, tillage frequency, and planting date. In both districts, using diff used light storage (DLS); hoeing twice, combined with big hills; and using recommended FR, combined with two FAs had signifi cant positive eff ects on yield and quality of seed potato. In both districts, if all farmers switched to the best management attribute levels, potential increases in seed yield would be about two times the actual seed yield produced in 2010. Th e results suggest that it is possible to design better methods to produce seed potato compared with methods that farmers currently use. Extension personnel could use these results to recommend to farmers those management attributes that are the most important to improve yield and quality of seed potato in Ethiopia.

SummaryIn many seed potato producing areas, micro-and minitubers are too small for direct planting as seed tubers in the field. Such use of these propagules can, however, be feasible if the crop's growth and development can be advanced. Increasing light interception, harvest index and yield of useable progeny tubers has been proved possible with plastic mulch and pre-planting of small tubers in a greenhouse. High amounts of nitrogen (up to 180 kg ha q) or deep planting (up to 9 cm) were less effective. Using older or pre-sprouted micro-or minitubers may be beneficial, because this might increase the number of sprouts per mother tuber (and thus stems per plant) or advance the growth of sprouts or stems. However, this would require even more careful management, due to the weakness of these sprouts and stems. Micro-and minitubers should be as large as feasible when used for direct planting in the field.

SUMMARYTransplant crops derived from in vitro produced plantlets of cultivars differing in earliness were grown in three experiments in three years in the Netherlands, during field periods of maximally 12 weeks. Seed tuber crops were included in the first year. Fresh tuber yield was analysed as the result of the radiation intercepted by the crop's canopy (AIR ; accumulated intercepted radiation), the efficiency of conversion of intercepted radiation into dry matter (RCC ; radiation conversion coefficient), the proportion of dry matter allocated to tubers (HI ; harvest index), and the tuber drymatter concentration (TDMC). Transplant crops had a lower AIR and lower yields than crops from seed tubers. Variables RCC, HI and TDMC were not affected by the type of propagule used. In transplant crops, yields from early cultivars could be extremely low when compared to later cultivars, due to a low AIR. This cultivar effect did not occur in crops from seed tubers. Among transplant crops, the lower AIR was the most consistent reason for lower tuber yields of earlier cultivars. It resulted from a slower increase in soil cover after transplanting and a lower maximum soil cover, both caused by a relatively high allocation of dry matter to tubers immediately after transplanting and resulting first in reduced haulm growth rates and subsequently also in reduced total growth rates. Senescence was not different. A higher HI partly compensated the lower AIR of the earliest cultivars. RCC and TDMC were not consistently affected by cultivar's earliness in the transplant crops.