Document Type : Research Article
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Abstract
Introduction: Before a new vineyard construction, in addition to collecting detailed data on climate, soil and planting area, some other considerations like selection and understanding the principles of quality and quantity in terms of agronomic traits and physiological characteristics of the product should be made. Among grape varieties grown in anorchard, some self-fertile and male sterile cultivars (female physiological) are present. Without suitable pollinating, varieties in the vineyard, is not accessible for semi-fertile or sterile ones with high quality and quantity and will notbe sufficient.Therefore the identification of sterile varieties, the best pollinizers and fruit growth and phenological stages is essential. Qzlouzum is one of commercial seeded cultivars in West Azerbaijan province whichis suitable for storage and delivering to domestic and foreign markets forout of season because of nice red color and thick skin and late ripening.These favorable properties for sale with high prices is also one of the otherbenefits that have led to the interest of the farmers every year to increase the acreage of the cultivation. Preliminary studies showed that Qzlouzum cultivar is a physiological female and needs cross pollination for fruitset. This study aimed to investigate the complete botanical characteristics, flower sexuality, pollen germination and determine the phenological stages (especially fruit growth stages).
Materials and methods: Based on grape descriptor, morphological characters of 10 vines of Qzlouzum grape cultivar at different stages from bud break to dormancy was studied in Horticultural Research Station in 1390 in Urmia(Kahriz). To calculate the growing degree days (GDD), daily temperature above 10 ° C was obtained from the meteorological station of Agriculture faculty in Kahriz-Urmia. Pollen germination rate was tested in both liquid and solid growth medium. In order to study the changes in a number of qualitative and quantitative traits, TSS (total soluble solids), TA (titrable acidity), pH, berry weight and diameter, seed length and weight from the beginning of the berry formation to harvest time of clusters in 15-day interval were measured.
Results and discussion: The results of this study showed that flowers of Qzlouzum are female with reflexed stamens. The results also determined that none of pollens germinated on both liquid and solid media culture. Based on reflexed stamens and none pollen germination, Qzlouzum grape cultivar proves to be male sterile (physiological substance). This cultivar needs 1483 degree days (above 10°C) from bud break till ripening. The changes in TA and TSS were reversed. Amount of acid reduced and sugar content increased with time and berry development. Veraision period was approximately started 55 days after full bloom. At this stage, which is also known as berry softening, acid concentration is reduced and the amount of sugar was increased. Acid content and pH of the fruit were opposite together and by reducing the amount of acid, the pH levels increased. Several studies have confirmed that after changing the color of the grape varieties,sugar can often increase. Conversely, acid reduction in berries is the first happensbefore color change in berries. The berry weight and size changes were described as Double Sigmoid Curve. In the first phase, berry diameter and weight increased rapidly and lasted 60 days. In the second phase or delay phase, berry weight and diameter changedvery slowly while seed weight reached themaximum in this stage. After this phase, the third phase which was associated began with veraision, sugar content increased and the amount of aciddecreased. At this stage berry reached its maximum size and weight.
Conclusion: Uniform planting of Qzlouzum red grapes is not recommended because of male sterility and suitable pollinizers should be used. Male sterility, without emasculation will be suitable for grape breeding programs. In areas with short growing season, if the total heat has not beensupplied, berries of this cultivar will ripe late and sugar contentand color intensity will decrease and will notproducedesired and marketable product. Phenological stages duration is highlydependent on factors such as cultivar, environment and location. Genetic factor also isparticularly important in determining the time of ripening. Qzlouzum is a late ripening grape cultivar and without sufficient thermal requirements, the ripening process will not occur completely.
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