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- Author or Editor: B.I. Reisch x
- Journal of the American Society for Horticultural Science x
Abstract
The in vitro shoot proliferation responses of 4 Vitis genotypes in the presence of 3 cytokinins was examined. All genotypes grew best in media containing 6-benzyladenine (BA), but the concentration response was variable. Kinetin had no effect upon the 2 interspecific hybrid cultivars but evoked a slight response with 2 genotypes of V. labrusca and V. labruscana. Adenine sulfate had no effect alone; however, when combined with BA, it decreased the rate of shoot proliferation. Addition of the auxin picloram (PIC; 0.1–2.5 μm) to BA-containing (5.0–10.0 μm) medium reduced the rate of shoot proliferation. Using low concentrations of PIC combined with 0.0 or 1.0 μm BA, there was a small increase in shoot tip multiplication. Callus growth was rapid in the presence of 5–10 μm BA and 1–2.5 μm PIC. In summation, the rate of shoot proliferation in grape shoot tip cultures is governed to a large extent by the interaction of cytokinins and genotypes.
The efficiency of marker-assisted selection for powdery mildew (Uncinula necator (Schw.) Burr) resistance in grapes (Vitis L. sp.) was studied using molecular markers associated with a major QTL (quantitative trait loci) for this trait. Initially, genetic maps were constructed from a segregating population of the cross `Horizon' × Illinois 547-1 (a hybrid between V. rupestris Scheele and V. cinerea Engelm.). A major QTL from Ill. 547-1, the resistant parent, explained 41% of the variation. One RAPD (randomly amplified polymorphic DNA) marker and one AFLP (amplified fragment length polymorphism) marker, obtained by bulked segregant analysis, showed the highest association with powdery mildew resistance in the mapping population. Segregation of the QTL was followed in different crosses by CAPS (cleaved amplified polymorphic sequence) markers developed from these two markers. An allele-specific amplified polymorphism that segregates as present/absent was also developed from the CS25b locus. Powdery mildew resistance was evaluated visually on a 1 to 5 scale in four different seedling populations. Two populations originated from crosses using Ill. 547-1 as the resistant parent. Two other populations were from crosses with NY88.0514.03, a resistant seedling from the original `Horizon' × Ill. 547-1 mapping population. Segregation ratio distortions were observed in some crosses. In these cases, the allele associated with the QTL for powdery mildew resistance was less frequent than the alternate allele. In all crosses, the markers were closely associated with resistance. If selection were based on markers, the percentage of susceptible individuals (classes 4 and 5) would decrease from 24% to 52% to 2% to 18%. Selection efficiency was greatest in crosses where segregation distortion was most intense.
Abstract
The hypothesis was tested that the growth of in vitro-propagated, nonrooted grape shoots (Vitis L. hybrid) directly after transfer from culture (ex vitro) is limited by photosynthetic C supply and that growth would be stimulated by CO2 enrichment (CDE). Plantlets were grown for 30 days in air with 350 or 1200 ppm (v/v) CO2 in humidified, flow-through chambers at 26°C. Destructive growth analyses were made at 0, 10, 20, and 30 days after transfer from culture to soil. CDE had no significant effect on total plant dry weight increase in the first 10 days. By 20 and 30 days, CDE-treated plants were 2 and 4 times greater in dry weight, respectively, than controls. Root growth was most improved by CDE, being almost 6 times greater than controls by 30 days. Leaf area per plant and root : shoot ratio were both doubled by CDE at 20 and 30 days. Since these results were under nonstress conditions, the use of CDE for growth stimulation needs to be evaluated under stress-hardening regimes.