Genetics and Plant Breeding Pointers 3 ✓

 

• Plant Breeding is the science that helps change the genetic makeup of plants for maximum economic output for human use.
• The basic chromosome/genomic number is X.
• The genetic chromosome number is denoted as n.
• The haploid number of Triticum aestivum is n = 21.
• Aneuploid refers to a heteroploid condition where one or few chromosomes are missing from 2n.
• Monosomic hypoploid is represented as 2n - 1.
• Double monosomic is represented as 2n - 1 - 1.
• Nullisomic is represented as 2n - 2.
• A hyperploid has one extra chromosome, termed trisomic (2n + 1).
• Double trisomic is represented as 2n + 1 + 1.
• The polyploidy level in the embryo and endosperm of seed is 3n.
• The polyploidy level of the testa and pollen mother cell of seed is 2n.
• The polyploidy level in the endosperm of Triticum aestivum is 63.
• Triploids are useful for producing seedless fruits.
• Wheat, cotton, tobacco, and oat are classified as allopolyploids.
• The term “primary centres of origin” was proposed by Vavilov.
• Apomixis refers to the development of vegetative embryos without fertilization.
• Parthenocarpy is the development of fruit without fertilization.
• Parthenogenesis describes when an embryo originates from an unfertilized egg.
• The progeny of a single cross-fertilized heterozygous individual is called an inbred.
• A male sterile line is referred to as an A-line.
• The progeny of a single plant obtained by asexual reproduction is known as a clone.
• A single gene that affects more than one character is known as pleiotropy.
• Back cross involves repeated crossing of hybrid progeny back to one of its parents.
• An F1 x homozygous recessive parent is called a test cross.
• Intra-specific hybridization occurs between two plants of different varieties.
• Self-pollination occurs when pollen grains from another flower fall on the receptive stigma of the same flower.
• Self-pollinated species are also known as autogamous species.
• Cross pollination or allogamy occurs when pollen from one plant is transferred to the receptive stigmas of another plant.
• Rice, wheat, buckwheat, and oat are examples of self-pollinated crops.
• Maize, pearl millet, black mustard, and sunflower are examples of cross-pollinated crops.
• Commonly cross-pollinated crops include safflower, arhar, cotton, and sorghum.
• Continuous inbreeding (selfing) leads to homozygosity.
• The single seed descent method is a method of self-pollination.
• Mass selection is always based on phenotype.
• The oldest selection method of crop improvement is mass selection.
• The concept of a pure line was given by Johnson.
• The progeny of a single homozygous self-pollinated crop is known as a pure line.
• The pure line selection method is used for breeding wheat.
• Bulk refers to the selection procedure where the segregating population of self-pollinated species is grown without selections.
• The most commonly used method for selection from segregating generations of crosses in self-pollinated crops is the pedigree method.
• The method that does not handle segregating populations is the bulk method.
• The pedigree method is used for improving specific traits such as plant height and disease resistance.
• Multiline breeding is widely exploited in the crop wheat.
• The method that does not provide an opportunity to practice selection for superior plants until F5 generations is the single seed descent method.
• The commonly used method for transferring disease resistance from one variety to another is the back cross method.
• Clonal selection is mostly used in the crop ginger.
• The parent used only once in back cross breeding is referred to as the donor.
• The bulk method was first used by Nilson Ehle in 1908.
• Progeny selection is also known as the ear-to-row method of selection.
• The methods used for handling the segregating generation are pedigree, bulk, and single seed descent method.
• A breeding method appropriate for improving a good variety is the back cross method.
• The method in which desirable scattered favorable genes are selected in different plants in each generation is called recurrent selection.
• The breeding method that is not appropriate for cross-pollinated crops is pure line selection.
• A cross between two genetically different homozygous plants is known as a hybrid or F1.
• A x B = F1 refers to a single cross hybrid.
• (A x B) x (C x D) represents a double cross hybrid.
• The equation selected variety/line/clone x open pollinated variety results in a top cross.
• The equation (A x B) x OP variety results in a double top cross.
• A variety produced by crossing all combinations of several lines that combine well with each other is called a synthetic variety.
• A synthetic variety is maintained by self-pollination.
• A variety produced by mixing the seeds of several phenotypically outstanding lines (varieties) is known as a composite variety.
• A composite variety is developed through cross-pollination.
• The hybrid variety was first exploited in maize.
• Chasmogamy is a mechanism of self-pollination in which flowers open only after pollination has taken place.
• Chasmogamy is found in rice, moong, and oat.
• Pollination and fertilization that occur before the opening of a flower is termed cleistogamy.
• Cleistogamy is found in wheat and barley.
• When male and female flowers of a hermaphrodite flower mature at different times, it is referred to as dichogamy.
• Protogyny occurs when the female matures before the male.
• Gaitonogamy is when pollen from a flower of one plant falls on the stigmas of other flowers of the same plant.
• A plant with both male and female flowers is termed monoecious.
• A plant with male and female flowers occurring on different plants is termed dioecious.
• Maize is classified as a monoecious plant.
• Papaya is classified as a dioecious plant.
• The first intergeneric hybrid was Raphino brassica (Radish x Cabbage).
• The hybrid variety of rice is developed using GMS and CGMS lines.
• Double cross hybrids of maize are developed using CGMS lines.
• The exploitation of hybrids in tobacco was carried out by Koelreuter.
• The superiority of F1 hybrids over both of its parents is termed as heterosis.
• The term “heterosis” was given by Shull.
• The average value for a character of the two parents of the concerned hybrid is called mid parent or average heterosis.
• When heterosis is estimated over the superior or better parent, it is called heterobeltiosis.
• When the superiority of the hybrid is compared to the standard commercial check variety, it is termed as economic heterosis.
• The exchange of chromatin between non-sister chromatids of homologous chromosomes is known as crossing over.
• Inbreeding depression refers to the loss or decrease in vigor and fitness as a result of inbreeding.
• Highly inbreeding depression is found in alfalfa and carrot.
• A sudden heritable change in any characteristics of an organism is known as a mutation.
• X-rays were first used as a mutagen by Müller.
• The unit in which mutation occurs is called a muton.
• A mutagen is a chemical or physical agent that greatly enhances the frequency of mutation.
• Triticale is a man-made cereal.
• The cultivated banana is classified as an autotriploid.
• The removal of the entire tassel (male inflorescence of maize) before pollen to initiate cross hybridization is called detasseling.
• A condition where either pollen is absent or non-functional in flowering plants is known as male sterility.
• When pollen sterility is caused by cytoplasmic genes, it is termed cytoplasmic male sterility (CMS).
• An important male sterility source of sorghum is Tift 60.
• Ethrel is used as a gametocide for wheat, rice, and sugarbeet.
• Wheat is classified as an allohexaploid.
• Sugarcane, cotton, and Brassica are classified as autopolyploids.
• Potato is classified as an autotetraploid.
• Brassica nigra evolved from B. compestris x B. oleracia.
• Brassica juncea evolved from B. compestris x B. nigra.
• Polygenic traits are characters governed/controlled by several genes, each having a small individual effect.
• The natural genetic engineer is Agrobacterium.