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  • Author or Editor: David P. Miller x
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Winter-hardiness of zoysiagrass (Zoysia spp.) cultivars is an important attribute throughout the biogeographical transition zone; thus, the inability to withstand freezing temperatures may limit the use of these cultivars. The objective of this research was to determine the freeze tolerance (LT50) of nine zoysiagrass cultivars grown in Raleigh, NC. Four Zoysia japonica Steud. cultivars (JaMur, Palisades, Empire, and Ultimate) and five Zoysia matrella (L.) Merr. cultivars (Pristine, Zeon, Cavalier, Diamond, and Zorro) were chosen to undergo freeze testing. Cores were taken from the field in Feb. 2008, 2009, and 2010 for the winter trials and in Apr. 2008, 2009, and 2010 for the spring trials (after green-up had occurred). The cores were subjected to freeze treatments of –6, –8, –10, –12, and –14 °C in programmable freezers. After thawing, cores were placed in a 41/20 °C greenhouse to promote green-up. Cores were rated for green-up after 4 weeks on a 1 to 9 scale. Nonlinear regression analysis was used to calculate an LT50 value for each cultivar. ‘JaMur’, ‘Palisades’, ‘Empire’, and ‘Ultimate’ were no different in the winter trials with an LT50 ranging from –9.8 to 10.2 °C. Among the matrella species, ‘Zeon’, ‘Cavalier’, and ‘Zorro’ were no different but ‘Diamond’ (LT50 of –6.0 °C) and ‘Pristine’ (LT50 of –5.7 °C) had less tolerance to freezing than the other matrella cultivars (LT50 range from –9.7 to –9.8), suggesting lower ability to cold-acclimate in the field than the other cultivars. Shoot weights of cores were correlated to visual green-up ratings for each cultivar with an R 2 range from 0.70 to 0.99 indicating a good relationship between the green-up ratings and shoot weights.

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Tomato is an important cash crop in many developing countries. However, smallholder farmers often lack access to improved cultivars and breeding programs to develop locally adapted cultivars are limited. Participatory crop improvement (PCI) approaches can be used to increase farmer access to improved cultivars. In this project, we used the mother and baby trial (MBT) design to introduce and evaluate tomato cultivars in three villages in the Morogoro Region of Tanzania. Mother trials were conducted in seven environments within the three villages, and variance partitioning revealed significant genetic effects for all traits measured with h 2 ranging from 0.74 to 0.90 for yield and disease reaction, respectively. In baby trials, farmers provided qualitative rankings of cultivars for 16 characteristics, including vigor, yield, harvest period, diseases, insect damage, fruit quality, and salability. Results from baby trials indicated that introduced cultivars were locally acceptable to farmers, except for traits related to marketability. Outcome Mapping was used to evaluate progress in each of the three villages and results suggested that high stakeholder participation levels could predict future adoption of introduced cultivars. Our findings provide a framework for evaluating, selecting, and breeding tomato and other horticultural crops in developing countries using the MBT design for PCI.

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