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  • Nyoka, B. I.  (2)
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  • 1
    Online Resource
    Online Resource
    Provenance Productivity of High and Low Elevation Pinus tecunumanii in Zimbabwe
    Walter de Gruyter GmbH ; 2010
    In:  Silvae Genetica Vol. 59, No. 1-6 ( 2010-12-1), p. 189-199
    Details
    In: Silvae Genetica, Walter de Gruyter GmbH, Vol. 59, No. 1-6 ( 2010-12-1), p. 189-199
    Abstract: The productivity potential of provenances and families of Pinus tecunumanii were determined across a range of environments in four orthogonal field trials in Zimbabwe. Provenances of P. tecunumanii from altitudes above 1500 m (High Elevation) in natural stands in Mexico and Central America were significantly superior (P 〈 0.05) to provenances from altitudes below 1500 m (Low Elevation) when planted in Zimbabwe in eightyear mean individual tree volume (1729.2 versus 1588.6 dm 3 ) at 1760 m a.s.l.; were not significantly different (1163.1 versus 1143.9 dm 3 ) at 1450 m a.s.l.; but the latter was significantly superior (1756.4 versus 1468.6 dm 3 ) at 1050 m a.s.l., and (720.7 versus 531.5 dm 3 ) at 780 m a.s.l. The most productive provenances were Juquila (26.1 m 3 ha -1 yr -1 ) at 1760 m, Yucul (17.3 m 3 ha -1 yr -1 ) at 1450 m, San Francisco (24.9 m 3 ha -1 yr -1 ) at 1050 m and Villa Santa (11.1 m 3 ha -1 yr -1 ) at 780 m a.s.l. Improved P. patula was significantly superior to P. tecunumanii at 1760 m a.s.l but the differences were nonsignificant at 1450 m a.s.l. In the warm lower altitude sites, P. tecunumanii was not significantly different from improved P. oocarpa, the commonly planted species, although some provenances of P. tecunumanii were significantly superior by as much as 31%. The top 10 ranked families of the high elevation P. tecunumanii had an eight-year volume advantage of 1% and 23% over P. patula at Stapleford and Cashel, and 40% and 34% over P. oocarpa at Gungunyana and Maswera respectively. Genotype-environment interaction was significant by elevation group, provenance and family level. The interaction at the family level was however largely contributed by families from the high elevation P. tecunumanii. Opportunities exist for immediate deployment of seed of selected provenances of P. tecunumanii in medium and low altitude areas to improve plantation productivity. There is however, no immediate yield advantage of using P. tecunumanii seed in high potential environments currently planted to P. patula. Breeding and selection could also bring about the planting of P. tecunumanii in the higher altitudes in the near future.
    Type of Medium: Online Resource
    ISSN: 2509-8934
    URL: Article
    DOI: 10.1515/sg-2010-0023
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2010
    detail.hit.zdb_id: 2210420-3
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Stem breakage and forking in low and high elevation Pinus tecunumanii
    Walter de Gruyter GmbH ; 2011
    In:  Silvae Genetica Vol. 60, No. 1-6 ( 2011-12-1), p. 1-8
    Details
    In: Silvae Genetica, Walter de Gruyter GmbH, Vol. 60, No. 1-6 ( 2011-12-1), p. 1-8
    Abstract: The incidences of stem breakage and forking at ages five and eight years in low and high elevation Pinus tecunumanii were assessed in multilocation provenance-progeny tests comprising 16 provenances of both low and high elevation P. tecunumanii . Stem breakage and forking were found to be more severe at the highest test site (1760m a.s.l.), and progressively declined with decreasing altitude. The mean stem breakage at individual sites for the two ages ranged from 0.7% to 19.5% in the low elevation P. tecunumanii , while that of the high elevation P. tecunumanii was between 0% and 12.9%. The mean percent of forked trees ranged between 3.9% and 46.8% in the low elevation P. tecunumanii and from 5.3% to 27.5% in the high elevation P. tecunumanii . The wide provenance variation in stem breakage and forking suggests that genetic factors related to seed source influence these traits. The low elevation P. tecunumanii had significantly higher incidences of stem breakage and forked trees compared to the high elevation P. tecunumanii . Overall, provenances with very low levels of stem breakage and forking included San Jerónimo, Montana Sumpul, Las Piedrecitas and Jocón. Although tested on a limited number of sites, the genotype* environment interaction at both provenance and family level appeared to be inconsequential. The mean percent of trees with stem breakage and forks increased between the two assessment ages, with changes ranging from small to more than double, implying that decision on selection against stem breakage and forking should be avoided at five years or earlier. The results of this study showed that the challenges of stem breakage and forking in plantations can be managed by one or a combination of site and seed source selection, while intensive breeding and selection could also be used as a long term strategy.
    Type of Medium: Online Resource
    ISSN: 2509-8934
    URL: Article
    DOI: 10.1515/sg-2011-0001
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2011
    detail.hit.zdb_id: 2210420-3
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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