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Potato is an important tuber crop that has a unique role in the food security of sub-Saharan Africa. Potato production faces several challenges, including limited sources of clean seed and the occurrence of nutrient deficiencies in plants. The availability of clean and viable seeds is the most prevalent challenge which necessitates the development of new strategies for enhancing production. Understanding the link between in vitro nutrient enhancement and seedling vigor in field conditions can assist in mitigating the adverse effects of these challenges after micro plant transplanting. In vitro experiments were set up to investigate the effects of calcium (Ca) fortification on several potato varieties, i.e. 'Shangi', 'Unica', and 'Dutch Robjyn' regeneration and microtuberization. Cuttings were subcultured onto modified MS media containing five levels of CaCl2 8.8 g L-1, 10.4 g L-1, 12 g L-1, 13.6 L-1, and 15.2 g L-1. Microtubers were initiated on media with 60 g L-1 brown sugar and 6 mg L-1 6-Benzylaminopurine. The experiment was set up in a completely randomized design with three replications. The regeneration capacity of the tested varieties differed significantly, as evidenced by shoot (p=0.0002) and root count (p=<.0001). The response of plants to fortification was variably dependent. The application of 10.4-13.6 g L-1 led to a significant increase (p<0.05) in root count in all three varieties. Furthermore, 13.6 g L-1 CaCl2 led to an increase in root-zone and mid-stem Ca content by 45%, 202%, and 165 % in 'Shangi', 'Unica', and 'Dutch Robjyn', respectively, compared to the control. The 'Dutch Robjyn' and 'Shangi' performed optimally in terms of regeneration and microtuberization, compared to 'Unica', under the effect of 10.4-13.6 g L-1 CaCl2. The results confirmed the optimization of MS regeneration by Ca enhancement as a potential technology for scaling up the production of clean quality seeds. [ABSTRACT FROM AUTHOR]

Clean seed systems for vegetatively propagated crops can play an important part in improving rural livelihoods but continue to face adoption challenges. Using exploratory case-based methodology, this research explored the adoption of a clean seed system for sweet potato (Ipomoea batatas) among farmers in the highlands of Papua New Guinea. The research further explored the outcomes driven by adoption and how system design influences adoption and outcomes. Data were collected through a baseline survey (n = 73) in 2017, and an end-line survey (n = 94) in 2020, with observation and field notes used to validate and verify survey results. Results provide insight into how a pragmatic approach to design, led by local extension staff, can provide a contextually relevant system that inspired widespread adoption. Adoption of clean seed has created a new market for vines, connected commercial farmers and commercial feedlots to improved agricultural inputs while increasing the interest of farmers in investing in complementary technologies to get the most from clean seed. [ABSTRACT FROM AUTHOR]

Abstract: Weedy rice is a great threat to rice production in Sri Lanka. Selective herbicides to manage weedy rice in conventional rice cultivars are not available in Sri Lanka. In the absence of appropriate chemical control measures, cultural approaches may help to achieve effective control of weedy rice. A study was conducted in two consecutive seasons in farmers' fields at three sites (Atalla, Samanthurai, and Girithale villages) in Sri Lanka to evaluate the effect of different establishment methods (farmers' practice, random broadcast, row seeding, seedling broadcast, and transplanted rice) on weedy rice infestation and rice yield. The farmers' practice had a higher number of weedy rice panicles (60–80 m−2) than the random broadcast (39–48 panicles m−2), seedling broadcast (3–15 panicles m−2), and transplanted rice (1.3–3.0 panicles m−2) methods. The use of clean rice seeds in the random broadcast method reduced weedy rice seed production by 29–41% compared with the farmers' practice (0.6–2.0 t ha−1). Compared with the farmers' practice, the seedling broadcast method reduced weedy rice seed production by 71–87% and transplanted rice by 95–98%; and increased rice yield by 27–49% (7.5–9.1 t ha−1). At all three sites, the farmers' practice resulted in the lowest grain yield (5.1–6.7 t ha−1). Compared with the farmers' practice, the random broadcast and row seeding methods increased rice yield by up to 21% and 31%, respectively. The findings suggest that the use of clean rice seeds, the use of a row-seeded crop, and the adoption of different rice planting methods may help to suppress the spread of weedy rice. [Copyright &y& Elsevier]

In a survey of wheat fields in northern Ethiopia, of 24 weed species observed nine were monocotyledons and 15 dicotyledonous. Dicotyledonous weeds made up 62.5% of the individual weed species and 83.1% of the total weed population, while monocotyledonous weeds were 37.5% and 16.9% respectively. Chrysanthemum segetum L. (corn marigold), Polygonum nepalense Meisn. (smartweed), Galium spurium L. (false cleavers), Spergula arvensis L. (corn spurrey) and Phalaris paradoxa L. (bristle-spiked canary grass), were the more important weeds with a frequency >30% and a dominance >5%. Polygonum nepalense and Spergula arvensis were dominant in the experimental wheat fi eld. In an experimental field use of clean wheat seed gave a significant reduction in the total weed population (P ≤0.05) and an increase in wheat height, tiller and ear-bearing tiller numbers and seed yield over plots sown to contaminated seed. Clean seed + 2,4-D, or a tank-mix of 2,4-D and fenoxaprop-p-ethyl, applied at 25 days after emergence (DAE) plus hand weeding (HW) at 45 DAE resulted in a significant reduction in weed population at 70 DAE (P ≤0.05). These treatments, and treatments in which two hand weedings were employed at 25 and 45 DAE, gave higher wheat yield and net benefit and were comparable with the weed free check. Clean seed + 0.72 kg ha-1 2,4-D + HW at 45 DAE, however, resulted in the highest benefit: cost ratio. Keywords: 2,4-D, clean seed, contaminated seed, fenoxaprop-p-ethyl, integrated weed management, wheat. [ABSTRACT FROM AUTHOR]