[Biology Class Notes] on Plant Breeding Pdf for Exam

Plant Breeding began with sedentary agriculture and the domestication of agricultural plants, a practice that dates back almost 9000 to 11000 years. Back then, the farmers just selected the food plants having some desirable characteristics. It has been practised globally by farmers and gardeners. It has also been employed by professional plant breeders who are employed by different organisations like universities, government institutions, research centres, or crop-specific industry associations.

The process known as participatory Plant Breeding is utilised by the farmers for getting involved in Plant Breeding constantly.  The international development agencies reckon that the breeding of new crops is essential for ensuring food security through the development of new varieties which are disease-resistant, higher-yielding, drought-tolerant, and regionally adapted for different growing conditions and environments.

Plant Breeding – Breeding for Disease Resistance requires

Plant Breeding is essentially the science of adjusting or modifying the traits of the plants to supply the required characteristics. One of the primary objectives of the Plant Breeding process is to supply the crop varieties that boost the superior as well as unique traits for the propagation of agricultural applications. Plant Breeding, also known as crop breeding, is accomplished using various techniques that start from selecting plants having desirable characteristics for the purpose of propagation, to using the data related to chromosomes and genetics.

The Different Types of Plant Breeding Processes

The various types of Plant Breeding processes that exist include Inbreeding, Backcrossing, Mutation breeding, Hybrid breeding, and Genetic engineering. All of these processes involve their own distinct methods as well as techniques that contribute towards the boost or productivity of the crops in several ways.

Plant Breeding and Genetics

Gregor Mendel (1822–84) is taken into account as the “father of genetics”. He has developed the laws of inheritance with the help of experiments with plant hybridization. Genetics stimulated research to enhance crop production through Plant Breeding.

Genetic modification of plants is achieved by adding a selected gene or genes to a plant, or by demolition of a gene with RNAi, to supply a desirable phenotype. The plants resulting from adding a gene are often mentioned as transgenic plants. If genetic modification genes of the species or of a crossable plant are used in check of their native promoter, then they’re called cisgenic plants. Sometimes genetic modification can produce a plant with the specified trait or traits faster than classical breeding because the bulk of the plant’s genome isn’t altered.

Modern Plant Breeding

Modern Plant Breeding is Applied Genetics, covering Biology, Cytology, Physiology, Pathology, Entomology, and Statistics. It has also developed its own technology.

Sometimes many various genes can influence a desirable trait in Plant Breeding. The use of tools like molecular markers or DNA fingerprinting can map thousands of genes. This allows plant breeders to screen large populations of plants for people who possess the trait of interest. The screening is predicated on the presence or absence of a particular gene as determined by laboratory procedures, instead of on the visual identification of the expressed trait within the plant. 

Classical Plant Breeding or Conventional Plant Breeding

One major technique of Plant Breeding is selection, the method of selectively propagating plants with desirable characteristics and eliminating or “culling” those with less desirable characteristics.

Conventional breeding relies largely on homologous recombination between chromosomes to get genetic diversity. The classical plant breeder can also make use of various types of in vitro techniques such as protoplast fusion, embryo rescue, or mutagenesis to get diversity and produce hybrid plants that might not exist in nature.

Traits that breeders have tried to include into crop plants include:

• Improved quality, like increased nutrition, improved flavour, or greater beauty

• Increased yield of the crop

• Increased tolerance of environmental pressures (salinity, heat, drought)

• Resistance to viruses, fungi, and bacteria

• Increased tolerance to insect pests

• Increased tolerance of herbicides

• Longer storage period for the harvested crop

Another technique is the deliberate interbreeding of closely or distantly related individuals to supply new crop varieties or lines with desirable properties. Cross breeding plants are used to introduce traits or genes from one variety or line into a replacement genetic background. 

Issues and Concerns related to Plant Breeding

Classical Plant Breeding, modern Plant Breeding, or Plant Breeding through the process of gene-splicing, each come with their own concerns related to the food crops. There is an ever-present question of whether the breeding process can have a negative impact on the nutritional value of the crops. 

According to one of the studies that was published in the Journal of the American College of Nutrition in 2004 with entitled changes in USDA Food Composition Data for the 43 garden corps between 1950 and 1999 compared the nutritional analysis of the vegetables between those years, it observed substantial decrease within 6 of the 13 nutrients that were measured. This includes 38% riboflavin and 6% protein. The reductions in phosphorus, vitamin C, iron, and calcium were also found. Thus the issues related to the nutritional value of the crops related to the process of Plant Breeding continues to be a relevant topic of discussion in the industry even today.

Role of Plant Breeding in Organic Agriculture

Critics of organic agriculture claim it’s too low-yielding to be a viable alternative to standard agriculture. However, part of that poor performance may be the result of growing poorly adapted varieties. Breeding varieties specifically adapted to the unique conditions of organic agriculture is critical for this sector to understand its full potential.

This requires selection for traits such as:

• Water use efficiency

• Nutrient use efficiency (particularly nitrogen and phosphorus)

• Weed competitiveness

• Tolerance of mechanical weed control

• Pest or disease resistance

• Abiotic stress tolerance (i.e. drought, salinity, etc…)

Plant Breeding helps to enhance biodiversity. It has given the greatest benefit, by the usage of its products. Compared to any other techniques Plant Breeding is found to be simple where the process and the crop improvement ideas are simple.