The commercial roses that you grow in your garden are normally the result of cross-pollination and are genetically highly heterozygous (the opposite of inbred), which in this case refers to most of the loci of plant being in a heterozygous condition or having two different alleles. If you wait too long, the pollen will be shed and the stigma may have received pollen from its own anthers. Emasculation happens at the bud stage before the pollen has been released and before the stigma is receptive. Because the flowers are perfect, you need to emasculate (remove the anthers from) the flowers you intend to use as the female. A breeding project should be started with a cross. ![]() Roses can self-pollinate or cross-pollinate. From a practical standpoint, if the rose is fertile you can use it in backyard breeding without much concern about whether it is diploid or tetraploid. Sterile roses cannot be used to breed new roses. Some roses are sterile because of triploidy or an imbalance in chromosome numbers, and never form rose hips. This optional journal article by Cédric Grossi & Maurice Jay on Chromosomes studies of rose cultivars provides more information on chromosome numbers. There are even triploid roses with 21 chromosomes. The large-flowered hybrid tea roses have four sets of chromosomes, so they are tetraploids with 28 (4 x 7 = 28) chromosomes. Some species, particularly wild species, are diploids with two sets of chromosomes, and so have a total of 14 (2 x 7 = 14) chromosomes. Roses have seven different types of chromosomes, so the total number of chromosomes in a rose is normally a multiple of seven. The species of rose differ in their chromosome number, or ploidy. In summary, the rose hip is an accessory fruit (parts other than ovary wall constitute the fleshy ripe portion) and an aggregate fruit (one flower, many carpels forming separate fruits) where the subsidiary fruits are achenes (optional). Within the hypanthium are hard achenes containing the rose seeds. The hypanthium is the structure that ripens into a bright red or red-orange fruit called a “hip,” recall that this is also the tissue that forms the fleshy part of the apple. (Refer to Chapter 8 if these are not familiar terms.) The base of the hypanthium is attached to the receptacle. ![]() The calyx, corolla, and androecium whorls are fused at their bases to form a small cup-shaped structure called a hypanthium that surrounds the ovary. Rose (genus Rosa with many species) is a perennial, mostly deciduous (they annually lose their leaves), mostly temperate-climate shrub in the Rosaceae family. Photo by Eastfield College Microscopy Lab, Mesquite, TX, CC BY-NC. Watch this video for an introduction to breeding roses and identifying rose hips (1:49) ![]() For both, breeding starts with a cross between two different plants (called a bi-parental cross). The strategies for the two plants differ because of how the final plant will be propagated. Roses are propagated asexually, while tomatoes are propagated by seed. This lesson presents examples of plant breeding of two common garden plants, rose and tomato. Recognize the difference that propagation method makes in a plant breeding program.Know the purpose of emasculation when making hybridizations (crosses) between parents.Understand how to get started breeding two common ornamental and food species.
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