Genetic and environmental variation in Vitex and cost analysis of a woody ornamental breeding program
Hershberger, Amanda Jannette
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Segregating populations of Vitex and their parents were cloned and grown in containers and in the ground. Traits evaluated included Cercospora leaf spot resistance, first flower date, last flower date, flower duration, total weeks of flowering, average inflorescence number, average inflorescence length, average flower rating, plant height, and plant width. Overall, plants grown in ground were taller and wider than their in container counterparts. In ground plants also had a later flower date, longer flower duration, greater total weeks flowering, longer average inflorescence length, larger average inflorescence number, and more flowers on the inflorescence. All flowering traits and most height and width measurements showed significant genotype by environment interaction. Therefore it is evident that genotypes react differently in each environment and selection should occur in one environment only and that environment is in ground. Those traits that exhibited entry X treatment interactions would suggest that by selecting those in containers would overlook optimal plants in ground and vice versa. Those plants that are among the top performers in ground may not be in containers, but could still perform better in containers than available cultivars in containers. High correlations were present in both environments between average inflorescence number and total weeks flower and between last flower date and total weeks flowering, First flower date and height measurements taken 33 weeks after planting, and average inflorescence number and last flower date were only correlated in ground, while total weeks flowering and flower duration were only correlated in containers. A breeder should be conscious of this as selection for one trait may also select for another. Costs per plant in ground were greater for both materials and labor. However, water usage was greatly reduced in the in ground trial. As cost analysis revealed higher costs in ground than in containers, it also revealed an extreme water use differential in which the container treatment received the most water. Many hours and materials costs were due to mulch which was received gratis through the university. It is not known how the lack of mulch application would affect overall water usage in ground. This additional cost for field growing plant material may become necessary as water use restrictions continue to be imposed.