Changes in Flower Size and Number Under Heat Stress in Rose (Rosa×Hybrida)
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Roses (Rosa × hybrida) have been one of the most popular decorations for entertainment and ceremonies for the past 5,000 years, and have been used in the fragrance, medicinal, and food industry. Heat stress is one of the most significant abiotic stresses which negatively affects rose performance and reduces the market value of roses. This project examined the effect of heat on rose in diploid rose populations created by intercrossing heat tolerant and sensitive diploid parents. Changes in flower size were examined in a heat shock (one hour at 44°C) experiment with potted plants and in field plots by comparing flower size in cool (spring and fall) versus warm (summer) seasons. As expected, the heat treatment decreased flower diameter, petal number, and flower dry weight. Flower size traits had moderately low narrow sense heritability (0.24 - 0. 35, 0.12 - 0.33, and 0.34 - 0.37) and moderately high to high broad sense heritability (0.62 - 0.67, 0.74 - 0.91, and 0.76 - 0.81) for flower diameter, petal number, and flower dry weight respectively. The G×E variance for flower diameter and flower dry weight accounted for 37% and 27% of the variance in the field experiment indicating that the heat stress had moderate differential genotypic effects as was indicated by the analysis of variance. However the genetic variance was several fold greater than the G×E variance indicating selection for flower size would be effective in any season but for the selection of a stable flower size (heat tolerant) rose genotype, selection would be required in both the cool and warm seasons. The number of flowers per primary and secondary inflorescence had very low narrow sense (0.01 and 0.06) and moderate broad sense (0.43 and 0.34) heritability. The G×E variance for the number of flowers per primary and secondary inflorescence accounted for 55.7% and 57.0% of the total variance in the field experiment indicating selection needs to be done for within each season. Only 26% of plants had tertiary inflorescences.
Liang, Shuyin (2016). Changes in Flower Size and Number Under Heat Stress in Rose (Rosa×Hybrida). Master's thesis, Texas A & M University. Available electronically from