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Cryopreservation for sugarcane (Saccharum spp. hybrids) germplasm conservation is well established. Virus elimination using droplet-vitrification (D-V) and cryo- or osmo-therapy has only been recently reported for sugarcane mosaic virus (SCMV). In this study, exposing large (3 mm) in vitro shoot tips of cultivars N12, N19, N58, and NCo376 infected with sugarcane yellow leaf virus (SCYLV) and NCo376 co-infected with SCMV and SCYLV were tested for virus elimination using both of the above-mentioned techniques. Cryo-therapy involved the exposure of infected in vitro shoot tips to the D-V protocol followed by recording recovery and virus-free shoot tips 16 wk after treatment. Osmo-therapy, consisting of the same treatment as cryo-therapy without immersion in liquid nitrogen (LN), was included for comparative purposes. Cryo-therapy resulted in 100% of the recovered shoots being SCYLV-free in cultivars N19, N58, and NCo376 and 83% in N12 when compared with untreated material. Osmo-therapy showed 58% (N12), 91% (N19 and N58), and 100% (NCo376) of shoots being clear of SCYLV when compared with untreated in vitro control plants (0 to 8%). Both techniques reduced the regrowth levels of treated shoot tips (22 to 57% recovery) when compared with untreated controls (92 to 97%). A novel finding of the study was that NCo376 co-infected with SCMV and SCYLV showed 100% virus-free recovered shoots after cryo-therapy and 92 to 100% of healthy shoots after osmo-therapy, compared with controls, which had 17 to 42% virus-free shoots. Plants from all cultivars that were re-tested 4 mo after hardening maintained their virus-free status. The described techniques for virus eradication offer a promising solution for the provision of clean vegetative planting propagules and safer germplasm exchange. [ABSTRACT FROM AUTHOR]

Biofortified orange-fleshed sweetpotato (OFSP), rich in beta carotene, is currently being promoted due to its role in fighting vitamin A deficiency. To promote farmer access to OFSP planting material (i.e., vines) projects establish vine multipliers who are expected to operate commercially. However, most sweetpotato farmers are used to getting vines from social networks free of cost. In this study, we compare farmers’ willingness to pay for clean (i.e., pest and disease free) vines of biofortified and popular non-biofortified sweetpotato varieties. The study thus holds vine “health” constant while assessing the influence of vitamin A biofortification on demand. We then use seemingly unrelated regression technique and data from 481 farmers to assess factors affecting the demand for both types of vines. We find higher willingness to pay for clean non-biofortified sweetpotato vines than biofortified sweetpotato vines of similar health, because of the higher nutritional value, good taste, and firmness of the roots of the former. Factors affecting demand for clean vines include the number of children a farmer has, farmer's age, tastes, preferences, sweetpotato yield and income. These effects differ between biofortified and non-biofortified varieties. We conclude that demand for clean OFSP vines is high, but still lower than for white-fleshed varieties, and discuss implications of the findings.

Commercialization of sweetpotato vines is persistent if multipliers show evidence of superiority of their vines. This study aimed at evaluating the effects of net tunnel source and of pathogen-tested planting material compared to “apparently” healthy vines on yield and health status at three defined environments in Northern Ghana during the rainy season of 2015. Sweetpotato virus disease (SPVD) and weevils were considered. Four varieties were investigated, the pathogen-tested vines of Dadanyuie, Bohye and Ligri, and “apparently” healthy vines of Apomuden from the negative selection technique. All planting materials taken from the net tunnel and open field were from the same location. Eight treatment combinations were arranged in a RCBD with 3 replicates. Planting distance was 0.30 m x 1 m. Weeding was done and fertilizer was applied as necessary. General and three-way analysis of variance were computed using Genstat. Highly significant differences were found among varieties and trial sites for plant establishment, foliage yield, root yield, weevil, and SPVD. The two sources were not significantly different. For varieties across sites, net tunnel source was better than open field. The apparently healthy vines might be effective as pathogentested vines. Net tunnels may have a distinct advantage for multiplication and maintenance.

Pathogen-tested foundation plant stocks are the cornerstone of sustainable specialty crop production. They provide the propagative units that are used to produce clean planting materials, which are essential as the first-line management option of diseases caused by graft-transmissible pathogens such as viruses, viroids, bacteria, and phytoplasmas. In the United States, efforts to produce, maintain, and distribute pathogen-tested propagative material of specialty crops are spearheaded by centers of the National Clean Plant Network (NCPN). Agricultural economists collaborated with plant pathologists, extension educators, specialty crop growers, and regulators to investigate the impacts of select diseases caused by graft-transmissible pathogens and to estimate the return on investments in NCPN centers. Economic studies have proven valuable to the NCPN in (i) incentivizing the use of clean planting material derived from pathogen-tested foundation plant stocks; (ii) documenting benefits of clean plant centers, which can outweigh operating costs by 10:1 to 150:1; (iii) aiding the development of disease management solutions that are not only ecologically driven but also profit maximizing; and (iv) disseminating integrated disease management recommendations that resonate with growers. Together, economic studies have reinforced efforts to safeguard specialty crops in the United States through the production and use of clean planting material.