Plant Breeding: Quiz 4 – Flashcards
Unlock all answers in this set
Unlock answers| Additive model |
A model for evaluating multiple alleles. An oversimplification. The number of beneficial alleles is added together. If dominant alleles are beneficial, aabbccdd = 0, and AABBCCDD = 8 |
| Allele frequency (q) |
f(A) = q = f(AA) + 0.5f(Aa) The sum of all allele frequencies is 1. A diploid organism has two alleles, either homozgous or heterozygous. The proportion of an allele in the population is its allele frequency. |
| Base population (C0) |
| May be an open-pollinated population, several open-pollinated populations, hybrids, or inbred lines. Diversity of genetic background is important: increases the chances that there are different fixed alleles, more room for improvement. The more vareities you use, the lower the starting mean, and the more time the breeding program will take, but higher the potential gain. |
| Betalain pigments |
| An alternative to red dyes found in red beets. |
| Cross-pollinated crops |
Natural mechanisms prevent self-pollination: dioecious, monoecious, self-incompatible, or have protandry. Pollination transfers randomly with no effort from the breeder. Not every locus is heterozygous, but some protion of the genome is heterozygous. The number of gametes produced is 2n, where n is the number of heterozygous loci. The number of possible genotypes produced is 3n. The number of cells in a Punnett square of a self-cross is 4n. |
| Dioecious |
| A natural mechanism to prevent self-pollination. Species have separate male and female plants. |
| Family selection |
Best for traits with low heritability; environment has a large effect on phenotype, so single-plant selections dont' give much indication of genotype. Logically, if a family with at least one common parent does better compared to other families, it is because it has good alleles from the parent(s), and therefore will provide good alleles for their progeny. There are three types of families: half-sib, full-sib, and S1. |
| Figs |
| Have pollen which can travel up to 14 km away, carred by wasps. |
| Full-sib |
| A type of family. Families produced from paired crosses. Have both parents in common. |
| Genotype frequency |
f(AA) + f(Aa) + f(aa) = 1 The frequencies of genotypes in a population. |
| Germ |
| The embryo in a corn seed. High in oil. |
| Grid-selection |
| Selecting plants from every grid on a field, increasing chances of a better selection in a non-uniform field. |
| Half-sib |
| A type of family. Families are produced by saving seed from an individual plant that was outcrossed with the population. Have only the mother in common. |
| Hardy-Weinberg equilibrium |
q2AA + 2q(1 - q)Aa + (1 - q)2aa = 1 Produces progeny with identical allele and genotype frequencies. Only true if: 1. There are two alleles 2. No selection 3. Random mating 4. No migration in or out of the populatoin 5. Equal mutation rate so that A to a equals a to A |
| High oil (IHO) |
| One of the four populations in the Illinois Recurrent Selection experiment. Levels are now at 20% oil, and still increasing. There is a relatively small ear, and a small kernel with a large germ. |
| High protein (IHP) |
| One of the four populations in the Illinois Recurrent Selecton experiment. Levels are now at 11% - 30% protein, and still increasing. There is a small ear, with a large cob, and a hard, flinty, translucent kernel with a medium dent. |
| Hybrid |
| Inbreeding of a cross-pollinated crop to produce homozygous lines that are crossed to produce hybrids, which may be sold as a hybrid variety. |
| Illinois Recurrent Selection experiment |
| In 1896, a recurrent selection program was initiated at the University of Illinois. From one base population, four populations were initiated: IHO, ILO, IHP, and ILP. After 45 years of improvement, new populations were produced from each of the four populations, reversing direction of selection, including RHO. In all cases, it was found that genetic variability still existed. |
| Independent culling |
| A method for selecting two traits. Selecting only families that fall into a certain quadrant when plotted on a graph for each trait. |
| Individual plant selection |
| Best for traits with high heritability. Not common in plant breeding, since most important traits have low heritability, or a breeder is selecting for many traits simultaneously. |
| Low oil (ILO) |
| One of the four populations in the Illinois Recurrent Selection experiment. There is a large ear, with a low row number, and a very large kernel, deeply dented, with a small germ. Approaching a physiological minimum near zero. |
| Low protein (ILP) |
| One of the four populations from the Illinois Recurrent Selection experiment. There is a large ear, with a relatively high row number, and a long, starchy kernel with little or no dent. Approaching a physiological minimum, near zero. |
| Marker |
| A polymorphism close to a gene. |
| Monoecious |
| A natural mechanism to prevent self-pollination. Species have separate male and female flowers. |
| No pollination control |
Produces half as much gain per cycle than pollination control. Equivalent to selection after pollination. Year 1: Open pollination of C0, followed by selection of best individuals. Year 2: Open pollination of C1 from bulk seed, followed by selection of the best individuals. |
| Pedigree selection |
| Gets rid of unwanted traits early, but only works for high heritablity traits. |
| Pollination control |
Twice as much gain per cycle than no pollination control, but takes twice as many cycles per year, equating it to no pollination control. Witer nurseries reduce time per cycle. Equivalent to selection before pollination. Year 1: Self-pollination with C0, select superior types at maturity. Year 2: Plant progeny rows of selected individuals, allow random pollination, and bulk seed at harvest. Year 3: Self-pollination within C1, select superior types at maturity. |
| Protandry |
| A natural mechanism to prevent self-pollination. Pollen is shed before the stigma becomes receptive. |
| Realized heritability |
R/S The proportion of selection differential realized in subsequent progeny. The degree to which environment influences phenotype. If 0, then selection has no effect. If 1, then the environment has no effect. |
| Recurrent selection |
Cyclical process that increases population means and allele frequencies incrementally with each cycle. Repeated selection and mating. Practiced until gain from selection becomes zero: genetic variability is exhausted. Gain from selection reduces over time, as genetic variation decreases. 1. Develop a base population 2. Evaluate individuals or their progeny 3. Select superior parents, and inter-mate randomly 4. Produce a progeny population, and return to step 2. |
| Red beets |
Beta vulgaris A cross-pollinated crop, pollinated by wind, with self-incompatibilit. Produces betalain pigments. Sugar interferes with the concentration of pigment. 25 US and 25 European varieties were used in a breeding program to increase pigment and decrease sugar. The realized heritability for pigment was 0.81, for sugar 0.27, and for selection index, 0.74. |
| Red dyes |
| Can be carcinogenic. Betalain pigments are a natural alternative. |
| Replication |
| A method for overcoming environmental influences in selection of traits wth low heritability. Related individuals are grown in different environments. |
| Response differential (R) |
| The difference between population means of the original population upon which selection was practiced, and progeny of selections. |
| Reverse high oil (RHO) |
| In the Illinois Recurrent Selection experiment, the ILO population that was then selected for high oil after 45 years. |
| S1 |
| A type of family. Produced from self-pollination of a plant. Mother and father is the same. There is no dilution of alleles. |
| Selection after pollination |
| Allow plants to inter-pollinate freely, and select individuals afterwards. Only gametes from females are selected. Gain from selection is half as much as selection after pollination. Difficult when selecting for traits that require pollination (yield, seed characteristics): family selection of progeny. |
| Selection before pollination |
| Removing undesirable plants from the field before pollen is shed. Both male and females are selected. Gain from selection is twice as much as selection after pollination. |
| Selection differential (S) |
| The difference between mean of selection and population mean. |
| Selection for a percent |
| When selecting for percentage, factors such as seed size and germ size can be affected, rather than yield. Need to be cautious. |
| Selection index |
A method for selecting for more than one trait at once. A single numerical value is assigned to assess phenotype, sometimes using economics or statistics. Example: [pigment]/[sugar] |
| Self-incompatibility |
| A natural mechanism that prevents self-pollination. A genetic mechanism. |
| Self-pollinated crops |
| Natural mechanisms ensure self-pollination. The flower may never open, open after pollination, or pollen is shed on the stigma as the flower opens. Frequency of self-pollination is dependent on species. Cross-pollination rate of 5% - 10% is common for self-pollinated crops. Landraces are heterozygous, homozygous, and produce all the same gametes: progeny are homozygous and homogenous. Considerable effort is made to transfer pollen artificially from one parent to another. |
| Tandem selection |
| A method for selecting for two traits. For several generations, select for one trait, then switch to selecting for the other trait. With no continuous selection for the frist trait, allele frequencies could decrease again. |
| Variety |
| For a cross-pollinated crop, an improved open-pollinated population can be sold as a variety. |
| Winter nursery |
| Allows pollination control to take half of the amount of time, doubling gain per year, making it better than no pollination control. Plants grown to have random pollination are grown over the winter in a warm location, such as Hawaii. |
| Winter nursery |
| Allows pollination control to take half of the amount of time, doubling gain per year, making it better than no pollination control. Plants grown to have random pollination are grown over the winter in a warm location, such as Hawaii. |
