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21.
Yohannes Petros Arnulf Merker Habtamu Zeleke 《Genetic Resources and Crop Evolution》2008,55(3):451-458
Genetic relationships and diversity of 45 Guizotia populations each consisting of ten individuals and belonging to five taxa of the genus Guizotia were analyzed using Inter Simple Sequence Repeat (ISSR) markers. Five ISSR primers generated a total of 145 scorable bands
across the 450 individuals used for the study. The percent polymorphic loci for the taxa ranged from 68.2 (G. arborescens) to 88% (G. scabra ssp. schimperi), with G. scabra ssp. scabra, G. zavattarii and G. villosa following G. scabra ssp. schimperi in this order with respect to the abundance of percent polymorphic loci. The Shannon-Weaver diversity indices (H′), for the
five taxa also followed a similar pattern, with G. scabra ssp. schimperi exhibiting the highest H′ (0.7373) and G. arborescens the least (0.5791), while H′ for G. scabra ssp. scabra, G. villosa and G. zavattarii were 0.7313, 0.6620 and 0.6564, respectively. The least genetic distance (0.1188) was observed between G. scabra ssp. schimperi and G.villosa, revealing closer genetic relationships of the two species with each other than with the others, and the highest genetic
distance (0.2740) was observed between G. scabra ssp. schimperi and G. zavattarii. The unweighted pair group method using the arithmetic average clustering of the five taxa using the standard genetic distances
produced two clusters, with G. scabra ssp. schimperi and G. villosa occurring in one cluster and G. scabra ssp. scabra, G. arborescens and G. zavattarii together in the other cluster. The study reveals that G. scabra ssp. schimperi is more closely related to G. villosa than to G. scabra ssp. scabra. 相似文献
22.
André Nel Francois S Malan Ron Braunstein C Brand Wessels Arnulf Kanzler 《Southern Forests》2018,80(2):159-168
A study was undertaken to evaluate the quality of the timber produced by Pinus elliottii × Pinus caribaea var. hondurensis (PECH) and the Pinus patula × Pinus tecunumanii low elevation (PPTL) and high elevation (PPTH) hybrids and their parent species for both kraft pulp and sawn-timber production. Trees were taken from unthinned tree improvement trials managed for pulpwood, ranging in age between 15 and 19 years. All sawn boards produced by study trees met the minimum wood density requirement for S5-grade structural timber (360 kg m?3), but approximately 17% of the boards failed to meet the other requirements for the grade, largely due to knot-related defects. Results of dynamic modulus of elasticity assessments performed on all of the boards suggested that a large percentage of boards would not meet the specified average stiffness (7 800 MPa). This was confirmed by the results of static bending tests performed on a subsample of boards. All boards tested for all species and hybrids met the required fifth percentile bending strength value for grade S7 (15.8 MPa) according to SANS 6122 (2008) specifications. The kraft pulping results indicated that the samples taken from the upper part of the stem yielded slightly better results on average than the samples representing the whole tree with respect to uniformity in the kappa vs charge and temperature, and yield vs kappa traits, with slight improvement of pulp yield (52% vs 50%) and some strength properties compared with whole tree pulping. Samples from the upper part of the stem had a close delignification rate in the 60–80 kappa range. The delignification rate for PPTL in the 60–80 kappa range was slower and the yield was slightly lower than P. patula (53.17% vs 52.72%) despite a higher kappa number. The pulp strengths short-span compressive test, breaking length and tearing strength of PECH were similar to those of P. elliottii, which were in turn generally lower than those of P. patula. The pulp strengths of PPTL and PPTH were similar to those of P. patula, whereas P. caribaea strengths were intermediate between those of P. patula and P. elliottii. With the exception of a slightly lower pulp yield, PPTL emerged as the best all-round hybrid for both pulp and sawn-timber properties. 相似文献
23.
The objective of the study was to investigate in vivo interspecific pollination success between Pinus radiata, P. maximinoi, P. oocarpa and P. tecunumanii. Pinus radiata was control pollinated with pollen lots of P. maximinoi, P. oocarpa and P. tecunumanii in a P. radiata seed orchard at Karatara (Southern Cape, South Africa). Pollination success was determined by counting the number of visible ovules, pollen grains inside and outside P. radiata ovules, as well as pollen tubes visible inside P. radiata ovules. Conelets were harvested and studied at eight time intervals, including 24 h after pollination, and weekly for 7 weeks after pollination. Histology studies with a standard fixation-dehydration-embedding sequence and paraffin wax method were used to determine the number of visible pollen grains inside versus outside the ovules and number of pollen tubes. Results indicated that pollen grains did sift through the cone scales within 24 h after pollination. However, P. radiata differed significantly (time by type of cross interaction) from the other three hybrid combinations in terms of number of visible ovules, visible pollen grains inside and outside of the ovules as well as pollen tubes, confirming limited interspecific hybridisation success. Future studies need to determine the percentage of fertile ovules in cross combination as a tool in predicting pollination success. 相似文献
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Robin AW Gardner Keith M Little Arnulf Kanzler Thimagren N Naidoo 《Southern Forests》2018,80(2):115-129
During 2001, a series of four site–taxa interaction trials was established in the warm temperate (mean annual temperature range 16–19 °C) forestry climatic zone of KwaZulu-Natal (KZN), South Africa. The main objective was to investigate the commercial forestry potential of a range of alternative Eucalyptus and Corymbia taxa for moderately dry (mean annual precipitation < 850 mm) sites within the zone. At rotation end, all trials received final standing tree measurements. At one of the sites (Rockvale), trees of eight promising alternative taxa were felled, stem measurements and wood samples taken, and wood and fibre productivities determined. On the basis of tree growth and wood and fibre production, C. citriodora subsp. variegata, C. henryi, E. badjensis, E. benthamii and E. dorrigoensis (listed alphabetically) demonstrated the greatest potential as commercial alternatives for moderately dry sites in the KZN warm temperate zone. The majority of these taxa showed strong site specificity. Eucalyptus benthamii was the only taxon showing high growth adaptability to the entire range of site conditions applied in the series. The non-susceptibility of C. citriodora subsp. variegata and C. henryi to the current topical insect pests Thaumastocoris peregrinus, Leptocybe invasa and Glycaspis brimblecombei elevates the appeal of these taxa as potential alternative planting choices for moderately dry sites within lower altitude (<1 100 m asl) areas of the climate zone. The matching of the most promising alternative taxa in the series to the range of sites encountered in moderately dry areas of the KZN warm temperate forestry zone is discussed in this paper. 相似文献