Two sweetpotato [Ipomoea batatas L. (Lam.)] cultivars, NASPOT 12 O (Namulonge sweetpotato 12 orange-fleshed) and NASPOT 13 O (Namulonge sweetpotato 13 orange-fleshed) were approved for release by the Ugandan Plant Variety Release Committee (UPVRC) in Nov. 2013 (Ssemakula et al., 2013). This brings to 22, the number of sweetpotato cultivars officially released between 1999 and 2013 by the National Sweetpotato Program in Uganda (Mwanga et al., 2011; Ssemakula et al., 2013). The two cultivars herein described and released in 2013, have high average storage root yields, 43.1 t·ha−1 (‘NASPOT 12 O’) and 27.8 t·ha−1 (‘NASPOT 13 O’) on station, and 14.9 t·ha−1 (‘NASPOT 12 O’) and 9.7 t·ha−1 (‘NASPOT 13 O’) on farm compared with the national on-farm average for Uganda of 4.5 t·ha−1 (FAOSTAT 2010; Low et al., 2009). The cultivars have acceptable root shape, high dry matter content (DMC) (>30%) with good-to-excellent consumer qualities. The cultivars also have moderate levels of field resistance to sweetpotato virus disease (SPVD) and alternaria bataticola blight. The two cultivars were bred targeting development of vitamin A–rich (biofortified) orange-fleshed sweetpotato (OFSP). OFSP have been shown to be both effective for increasing maternal and child vitamin A intake and status (Hotz et al., 2012; Ruel and Alderman, 2013). The potential of the two OFSP cultivars to contribute to food and nutrition security in Uganda and the developing world is high (Low et al., 2007; Ruel, 2001), especially where high dry matter and starchy sweetpotatoes are preferred. The cultivars can be used directly if adapted in similar agroecologies in sub-Saharan Africa and globally and/or used as parents in breeding programs to develop locally adapted cultivars that meet high dry matter consumer preferences.
Origin
Before release, ‘NASPOT 12 O’ and ‘NASPOT 13 O’ were code named SPK004/2006/1136 and NASPOT7/2006/292, respectively. SPK004 (released in 2004 as Kakamega) was the female parent, 2006 was the initial year of clonal selection, and 1136 was the genotype number. This clone was officially released as ‘NASPOT 12 O’ [NASPOT = Namulonge sweetpotato, 12 = serial number according to the UPVRC and the National Agricultural Research Organization (NARO) nomenclature, O = orange fleshed]. Similarly, ‘NASPOT 13 O’ is a progeny of the released cultivar, with ‘NASPOT 7’ first selected in 2006 as genotype number 292, and given the UPVRC/NARO serial number 12, and officially released as ‘NASPOT 13 O’. Kakamega (SPK004) was the female parent of ‘NASPOT 7’; therefore, ‘NASPOT 7’, ‘NASPOT 12 O’, and ‘NASPOT 13 O’ are genetically related.
The polycross block from which the two cultivars originated was established in 2005/2006 at Namulonge with 24 parents (Table 1). The 24 parents in the polycross block consisted of three released and three common Ugandan landrace cultivars, two bred released Ugandan cultivars, three Ugandan breeding lines, and introductions from Kenya (2), Peru (8), and Rwanda (3). ‘NASPOT 12 O’ and ‘NASPOT 13 O’ are progenies of ‘Kakamega’ as the female parent, but because seed was open pollinated, their male pedigrees are unknown. The parents were included in the polycross nursery for improvement or as sources of one or a combination of genes for combining desirable traits such as orange-fleshed roots (provitamin A), high dry matter (≥30%), resistance to SPVD and alternaria bataticola stem blight, and early maturity (3 to 4 months).
Origin and main attributes of 24 sweetpotato parents in the polycross nursery at Namulonge in 2005/2006 that gave rise to lines from which ‘NASPOT 12 O’ and ‘NASPOT 13 O’ were selected.z
Description and Performance
The key standard morphological descriptors [International Potato Center (CIP), Asian Vegetable Research and Development Center, and International Board for Plant Genetic Resources, 1991] of the two released cultivars are listed in Table 2 and major differences are shown in Fig. 1. Both cultivars have semierect vines and vigorous growth. However, ‘NASPOT 12 O’ has dense foliage that suppresses aggressive weeds, and a balanced harvest index that makes it good for dual purpose use as animal feed and food (Claessens, 2009). The flower color in both cultivars is the same, pale purple limb with purple throat. Flowering and seed capsule set are sparse in both cultivars. Both cultivars have high storage root DMC (≥30%) and a dry texture with a sweet taste when cooked (Table 3). Storage root skin color is purple red in ‘NASPOT 12 O’ and cream in ‘NASPOT 13 O’. The storage root flesh color in both cultivars is deep orange but the intensity varies with age of the roots, location, and agro–climatic factors such as soil type, and wet or dry season.
Morphological descriptors of ‘NASPOT 12 O’ and ‘NASPOT 13 O’ released in Uganda in Nov. 2013.z
Morphological characters of ‘NASPOT 12 O’ (A) shoot and flower, (B) shoot tip, leaf and root, and ‘NASPOT 13 O’ (C) shoot and flower, and (D) shoot tip, leaf, and storage root.
Citation: HortScience 51, 3; 10.21273/HORTSCI.51.3.291
Morphological characters of ‘NASPOT 12 O’ (A) shoot and flower, (B) shoot tip, leaf and root, and ‘NASPOT 13 O’ (C) shoot and flower, and (D) shoot tip, leaf, and storage root.
Citation: HortScience 51, 3; 10.21273/HORTSCI.51.3.291
Morphological characters of ‘NASPOT 12 O’ (A) shoot and flower, (B) shoot tip, leaf and root, and ‘NASPOT 13 O’ (C) shoot and flower, and (D) shoot tip, leaf, and storage root.
Citation: HortScience 51, 3; 10.21273/HORTSCI.51.3.291
Main agronomic disease and insect pest reaction and quality traits of two orange-fleshed sweetpotato cultivars released in Uganda in Nov. 2013.
Ssemakula et al. (2013) presented the data for official release of the two cultivars in Uganda. Details of the release information include descriptions of pedigree, cultivar, test sites, materials and methods, planting materials, on-station and on-farm trials, planting and harvesting dates, pest and disease evaluation procedures, farmer selection, acceptability evaluation, experimental designs, stability analysis, determination of dry matter and beta-carotene, corresponding results, and cultivar maintenance. The following description is a summary of the cultivar release results. The released cultivars were tested for six seasons (Uganda has two rainy seasons per year when sweetpotatoes can be grown) on station and on farm during 2011 to 2013 in replicated, standard multilocation yield trials in 1) the warm, subhumid short grasslands where sweetpotato weevils and drought are important and frequent; 2) the warm, moist, tall grasslands where SPVD pressure is high; and 3) the cool, moist, southwestern highlands where alternaria bataticola blight and low soil fertility problems are widespread. A total of eight multilocational on-station trials were conducted for four seasons, followed by 100 on-farm trial evaluation for two seasons under rain-fed conditions. The cultivars were routinely evaluated for resistance to SPVD, alternaria bataticola blight, and sweetpotato weevils, Cylas puncticollis (Boheman) and Cylas brunneus (Fabricius) (Table 3). Classification of the relative resistance to disease and weevil damage was based on field evaluation under natural disease pressure and weevil populations in each agroecology. Storage root DMC, root yield, taste, and desirable agronomic attributes (such as earliness, root size, and shape) were also evaluated (Table 3). Data were subjected to analysis of variance using SAS statistical package (SAS V9.1; SAS Institute, Cary, NC). Treatment means were separated where appropriate, using Fisher’s least significant difference test.
Results of the performance of the cultivars on station and on farm including palatability are presented in Tables 4 and 5. Both ‘NASPOT 12 O’ and ‘NASPOT 13 O’ have higher storage root and biomass yield, higher harvest index, and higher SPVD field resistance than the control cultivar, Dimbuka-Bukulula (Table 4). For most traits, the two cultivars performed as well as or better than the local checks across districts (Table 5). The two cultivars have higher beta-carotene in storage roots than Dimbuka-Bukulula (Table 2). These two cultivars have moderate beta-carotene content compared with cultivars such as Resisto with high beta-carotene values (17–25 mg/100 g, on a fresh weight basis) (Grüneberg et al., 2015; Tumwegamire et al., 2014). Both cultivars have moderate field resistance to SPVD and alternaria blight, but are susceptible to weevils, though ‘NASPOT 12 O’ tends to be less susceptible because of the thick canopy that creates a humid microclimate that is not conducive to weevil colonization. Both cultivars are highly susceptible to the pests in no-choice tests under laboratory conditions. However, both cultivars are potentially valuable as sources of beta-carotene in a high DMC background, and they are already used as parents in the crossing block at Namulonge in Uganda. These cultivars are expected to perform well in agroecologies with low-to-moderate SPVD pressure and with well-distributed rainfall for the first three months during growth.
Performance of ‘NASPOT 12 O’ and ‘NASPOT 13 O’ in advanced yield trial at four on-station sites, Namulonge, Kachwekano, Ngetta, and Serere, for two seasons in 2011–12.z
Performance of ‘NASPOT 12 O’, ‘NASPOT 13 O’, and local checks (LC) during two seasons in on-farm sweetpotato trials in various districts of Uganda during 2012.
Dissemination of Cultivars
‘NASPOT 12 O’ and ‘NASPOT 13 O’ are currently grown by local farmers where on-station and on-farm trials were conducted and in districts where HarvestPlus and collaborating partners promote dissemination of OFSP cultivars to alleviate vitamin A deficiency. A total of 100 households hosted the on-farm trials in six districts. Clonal propagation of the disseminated cultivars assures maintenance of genetic purity of sweetpotato cultivars at farm level. Some farmers and vine multipliers renew propagation material to avoid degeneration due to virus infection and indirectly maintain clonal purity. The districts of OFSP production currently include, Isingiro, Buyende, Rakai, Oyam, Bushenyi, Kabale, Kamwenge, Wakiso, Mukono, Mpigi, Soroti, Gulu, Lira, Kisoro, Mbarara, Masaka, Kibaale, Kole, and Kamuli. In the absence of promotions, the spread of the cultivars is mainly through farmer-to-farmer exchange or sale of planting materials.
Availability
The cultivars are maintained as pathogen-tested plants in the screenhouse at the Quarantine Station, Muguga, Kenya, and are maintained in the field by National Crops Resources Research Institute in Uganda. Requests for these cultivars should be addressed to: Seed Unit, CIP, P.O. Box 25171, Nairobi, Kenya. Requests for planting materials within Uganda should be directed to: Root Crops Program, NaCRRI, P.O. Box 7084, Kampala.
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