Pureline and Mass selection methods of plant breeding

Plant breeding is the process of manipulating plant species in order to create desired traits, such as increased yield, disease resistance, or improved nutritional content. It involves careful selection and crossing of plants with desirable characteristics over several generations to achieve the desired outcome. Introduction to pureline selection, characteristics of pureline, history, applications of pureline selection, general procedure of pureline selection, advantages and disadvantages of pureline selection, achievements.
Introduction to mass selection, applications of mass selection, Procedure of mass selection, merits of mass selection, demerits of mass selection, achievements of mass selection, difference between mass and pureline selection.
In pureline a large number of plants are selected from a self pollinated crop and are harvested individually, individual plant progenies from them are then evaluated, and the best progeny is released as a pureline variety. Therefore pureline selection is also known as individual plant selection.
In mass selection, a large number of plantsof similar phenotype are selected and their seeds are mixed together to constitute the new variety.
Mass selection is used for improvement of local varieties. Also used for purification of existing purelines.
Mass selection is a plant breeding method where plants with desirable traits are selected and allowed to interbreed to produce the next generation. It's a relatively simple approach, often used in the early stages of breeding programs to improve traits such as yield, disease resistance, or adaptation to specific environments. However, it may not be as precise or efficient as other breeding methods, such as pedigree selection or molecular breeding techniques.
Pureline selection is a breeding method focused on selecting and propagating individual plants that consistently exhibit desirable traits from generation to generation. It involves isolating plants with specific characteristics and allowing them to self-pollinate, ensuring genetic uniformity within the resulting offspring. This method is particularly effective for traits controlled by single genes and is commonly used to develop pure, uniform varieties in crops.

1. Government Vidarbha Institute of Science & Humanities (Autonomous), Amravati DEPARTMENT OF BOTANY TOPIC NAME : PURELINE AND MASS SELECTION AS METHOD OF BREEDING IN AUTOGAMOUS CROPS Presented by : NAME : NEHA MOTIRAM KAKADE CLASS : BSC III RD year 2023-2024 BATCH : P1 SEM : V TH SUB : BOTANY (PLANT BREEDING AND RESEARCH METHODOLOGY )

2. Table of content P ureline selection Introduction Characteristics of pureline History Applications General procedure Advantages Disadvantages Achievements Mass selection Introduction Applications Procedure Advantages Disadvantages Achievements Comparison table between pureline and mass selection

3. Pureline Selection A pureline is a progeny of a single ,homozygous ,self pollinated plant . In pureline selection ,a large number of plants are selected from a self pollinated crop and are harvested individually, individual plant progenies from them are evaluated , and the best progeny is released as a pureline variety. Therefore pureline selection is also known as individual plant selection . A pureline variety is a variety obtained from a single homozygous plant of a self pollinated crop i.e., is a pureline . In self-pollinated crops, pureline varieties are far more better than mixtures of purelines .

4. Characteristics of purelines All the plants within a pure line have the same genotype as the plants from which the pureline was derived. This is because the parent plant was homozygous and self fertilized. The variation present within a pure line is environmental and non- inheritable. Since all the plants within a pure line are of identical genotype the variation present within a pure line is due to environment only. Therefore, selection within a pure line will generally not be effective. Purelines become genetically variable with time. The genetic variation is produced by mechanical mixtures, natural hybridization or mutation. Mechanical mixture and natural hybridization can be prevented by careful handling of purelines . However, spontaneous mutations would produce genetic variability in due course of time. Man can do nothing about it, accept that he may attempt to maintain the purity of purelines through repeated mass selection.

5. History of pureline selection Pureline Selection dates back to mid-nineteenth century or even earlier. Between 1840 and 1860, several workers, notably, Le couteur , Shrieff , Hallet and Vilmorins , practised individual plant selection in crops like wheat , barley and sugarbeets . Loui de Vilmorin proposed the Vilmorin principle or Vilmorin isolation principle, which is the basis for progeny test. The genetic basis of purelines was explained subsequently by Johannsen in 1903 .

6. APPLICATIONS OF PURELINE SELECTION Pureline selection has several applications in the improvement of self-pollinated crops. It is used to improve local or desi varieties, old pureline varieties and introduced varieties. Improvement of Local Varieties Pureline selection is the favourite method for the improvement of local varieties that have considerable genetic variability. A large number of varieties have been developed by this method. Some examples of such varieties are: NP 4 and NP 52 wheat, NP 11 and NP 12 linseed . Pureline Selection in introduced varieties Introduced materials are often subjected to pureline selection to develop suitable varieties. Several pureline varieties have been developed in this way. Shining Mung 1 is a pureline selection from the introduced variety Kulu Type 1, and PS 16 is a selection from an introduction from Iran.

7. Improvement of Old Pureline Varieties Purelines become variable with time. Often selection is used to isolate new pureline varieties from such genetically variable purelines . Some examples of pureline varieties isolated from old pureline are: Chafa (from No. 816) gram; Jalgaon 781 (from China Mung 781), Khargone 1 (from K 119-56), Pusa Baisakhi (from T 44), CO 2 (from PLS 365/3) .Sometimes off-type plants appear in purelines . Such off-type plants may be selected to develop new pureline varieties. A dwarf off-type plant was selected from the tall scented pureline variety of rice Kalimoonch 64, and released as a new pureline variety Shyama. Selection for A New Characteristic in a Pureline Sometimes an opportunity for pureline selection arises when there is a need to select for some new character, which was not previously important. Such a character may be resistance to a disease, plant type, grain type etc. An example of such a selection is the isolation of Jowar (S. bicolor) variety resistant to root rot caused by Periconia circinati . Selection in the Segregating Generations from Crosses Purelines are generally selected from the segregating generations of crosses. Purelines in such cases may be selected using pedigree, bulk or backcross method.

8. A GENERAL SCHEME FOR PURELINE SELECTION

9. A GENERAL SCHEME FOR PURELINE SELECTION A general procedure for pureline selection is described below . The number of years required for any step in the procedure and the procedure itself may be modified according to the specific needs of a breeding programme . The pureline selection has the following three steps: (1) selection of individual plants from a local variety or some other genetically variable and homozygous population, (2) visual evaluation of individual plant progenies, and (3) yield trials. Step One First Year A diverse set of 200-3,000 plants from a local or genetically variable population is chosen, and their seeds are harvested separately for evaluation, ideally allowing for proper spacing to observe and select individual plants or, if necessary, individual heads or stems. The number of plants to be selected depends upon the breeder's discretion. However, it should be kept in mind that the selected plants will be homozygous Selecting superior genotypes from a mixed population with 2,000-3,000 randomly chosen plants is recommended to capture genetic variation between plant progenies; however, with a smaller sample, careful selection for superior types should be made. In any case, it is advisable to select for easily observable characters, such as, flowering and maturity times, disease resistance, presence of awns, plant height etc. If desirable types are not included in the initial selection, they cannot be expected to be present in the progeny.

10. Step Two Second Year Progenies from individual plants are grown separately with proper spacing. The objective of this step is to drastically reduce the number of plant progenies to be carried to step three. This is because step three requires substantial land, labour , time and funds. Visual evaluation rejects poor progenies, retaining promising segregating ones. Selection for simpler-inherited traits like plant type, height, grain type, and disease resistance is prioritized. Superior pureline progenies are harvested, reducing their number for efficient replicated yield trials in the next step.Disease epiphytotics may be created to test the progenies for disease resistance. If considered necessary, this process may be repeated for one or more years. But this is usually not done.

11. Step Three This step consists of replicated yield trials for a critical evaluation of the selected progenies. Third Year If individual plant progeny seeds are insufficient for a replicated trial, an unreplicated trial is conducted, with the best variety used as a check for comparison. Selection is based on observable traits, particularly disease resistance. A preliminary yield trial is conducted if enough seed is available, using yields as a selection criterion to further reduce the number of progenies. Fourth Year Breeder conducts replicated yield trials, using the best variety as a check, recording observations on disease resistance, flowering, maturity times, and other traits. Superior progenies are identified based on these and yield data, with quality tests as a potential criterion. Each progeny, being a pureline , is treated as a strain. Promising strains proceed to coordinated yield trials for further evaluation. Fifth to Seventh Years. The promising strains are evaluated at several locations alongwith strains from other breeders. The best released varieties are used as checks. Eighth Year. The best progeny or strain is released as a new variety and its seed multiplication is initiated for distribution to the farmers. The time required in each step may be more or less than that outlined in the above scheme depending upon several factors. For example, if enough seed is available from the second year, preliminary yield trial should be conducted in the third year; this would save one year.

12. Pureline selection achieves the maximum possible improvement over original variety. This is because the variety is the best pureline present is the population. Pureline varieties are extremely uniform since all the plants in the variety have the same genotype. Such a uniform variety is more liked by farmers and the consumers than a less uniform variety developed through mass selection. Due to its extreme uniformity, the variety is easily identified in seed certification programmes . ADVANTAGES OF PURELINE SELECTION

13. The varieties developed through pureline selection generally do not have wide adaptation and stability in production possessed by the local or desi varieties from which they are developed . The procedure of pureline selection requires more time, space and more expensive yield trials than mass selection. The upper limit on improvement is set by the genetic variation present in the original population. The breeder has to devote more time to pureline selection than to mass selection. This leaves less time for other breeding programmes . Disadvantages of pureline selection

14. ACHIEVEMENTS Pureline selection was the most extensively used breeding method in the early days of crop improvement work in India. At that time, genetically variable desi or local varieties were available that offered excellent opportunities for pureline selection. A large number of improved varieties were developed by this method in self-pollinated crops like wheat (T. aestivum), barley (H. vulgare), rice (O. sativa), pulses, e.g gram (C. arietinum), mung (V. radiata), urid (V. mungo) etc., oilseeds, eg groundnut (A. hypogaea), linseed (L. usitatissimum ), self-compatible species of Brassica viz. ral (B. juncea ), toria (B. campestris var, toria ), tobacco (Nicotiana spp.), cotton (Gossypium spp.). Jowar (S. bicolor), jute (Corchorus spp.), many vegetables etc. The examples of varieties developed through pureline selection are too numerous to be enumerated. It may be pointed out that for a long time varieties developed through pureline selection dominated the Indian agriculture.

15. mass selection In mass selection, a large number of plants of similar phenotype are selected and their seeds are mixed together to constitute the new variety. The plants are selected on the basis of their appearance or phenotype. Therefore, selection is done for easily observable characters like plant height, ear type, grain colour , grain size, disease resistance, tillering ability, lodging resistance, shattering resistance ,yield ete . Population from selected plants is more uniform, especially for easily observable traits governed by major genes, but may show variation in quantitative characteristics. The selected population is a mixture of homozygous plants from the original diverse population, resulting in a variety with genetic variation. Additional mass or pureline selection may be needed in the future.

16. APPLICATIONS OF MASS SELECTION In case of self-pollinated crops, mass selection has two major applications: (1) improvement of desi or local varieties, and (2) purification of the existing pureline varieties. Improvement of Local Varieties Mass selection enhances local self-pollinated crop varieties by removing inferior plant types, improving overall performance and uniformity. This method preserves adaptability and stability as the improved variety comprises most superior purelines from the original local variety, which is well-adapted and stable over time. Purification of Existing Pureline Varieties The other application of mass selection is to maintain the purity of existing pureline varieties. Purelines tend to become variable with time due to machanical mixtures, natural hybridization and mutation. It is, therefore, necessary that the purity of pureline varieties be maintained through regular mass selection. At present, mass selection is used precisely for this purpose, and the nucleus seed of pureline varieties is produced through mass selection. Thus as a breeding method, mass selection has only a limited application for the improvement of self-pollinated crops . While it has limited application for improving self-pollinated crops, it is crucial for preventing inbreeding in cross-pollinated species. Inbreeding is avoided or minimized through mass selection, making it particularly significant for maintaining vigor and yield in these species.

17. THE PROCEDURE OF MASS SELECTION

18. THE PROCEDURE OF MASS SELECTION The general procedure for mass selection in developing a new variety is outlined below and is schematically represented in Fig. 11.1. But the procedure may be modified by the breeder according to the needs of his programme . First Year . A large number of phenotypically similar plants are selected for their vigour , plant type, disease resistance and other desirable characteristics. The number of plants selected may vary from few hundred to few thousand. If too many plants are selected, the improvement is likely to be small. But if too few plants are selected, the adaptation of the variety may become poor. Seeds from the selected plants are composited to raise the next generation. Second Year . The composite seed is planted in a preliminary yield trial along with standard varieties as checks. The variety from which the selection was made should also be included as a check to determine if there has been an improvement due to selection, Phenotypic characteristics of the new variety are critically observed

19. Third to Fifth Years The new line is evaluated in coordinated yield trials. at several locations. This is done to test the performance of the new line at different locations within an agroclimatic zone and compare it with that of the popular commercial varieties used as checks. First, the new line is evaluated in an initial evaluation trial for one year. If the line is promising, it is promoted to uniform regional trials for two or more years. If found promising, the new line will be identified for release as a new variety. Seventh Year The new line may be released as a new variety for cultivation if found suitable and if recommended by the Central or State Variety Release Committee. Two variations of mass selection are given below to serve two different objectives. In improving a local variety a large number of plants are selected and their seeds are harvested separately. The number of plants may range from several hundred to few (2 or 3) thousand. In the second year, individual plant progenies are grown for progeny test. Poor, weak and defective progenies are rejected. Progenies from heterozygous plants are also discarded. Care should be taken not to discard more than 20-25 per cent of the progenies. Seeds from the remaining progenies are mixed together to make-up the new variety. In the third and fourth years, the variety is subjected to yield trials in different environments to check its performance and adaptability. The new variety is quickly released since it would retain the adaptation of the original variety with a superior performance. Thus prolonged testing is not necessary, this reduces the cost and the time required for developing the new variety

20. The second variation of mass selection is used for the purification of existing pureline varieties. In the first year, 2-3 hundred or more plants are selected and harvested separately from the pureline to be purified. The plants selected are those typical for the variety. In the second year, progenies from the selected plants are grown and observed critically. Progenies which are different from the typical features of the concerned variety are rejected. The remaining progenies are mixed together to constitute the concerned variety. This process may be repeated every few years or as often as it is found necessary to keep the variety pure. This procedure is followed. to produce the basic seed of pureline vaneties , the basic seed is used for the production of breeder seed.

21. MERITS OF MASS SELECTION 1. Since a large number of plants are selected, the adaptation of the original variety is not changed. It is generally accepted that a mixture of closely related purelines is more stable in performance over different environments than a single pureline . Thus varieties developed through mass selection are likely to be more widely adapted than purelines . 2. Often extensive and prolonged yield trials are not necessary. This reduces the time and cost needed for developing a new variety. 3. Mass selection retains considerable genetic variability in the new variety. Therefore, another round of mass selection after few years would be effective in improving the variety further. 4. It is a less demanding method. Therefore, the breeder can devote more time to other breeding programmes .

22. DEMERITS OF MASS SELECTION 1. The varieties developed through mass selection show variation and are not as uniform as pureline varieties. Therefore, such varieties are generally less liked than pureline varieties. 2. The improvement through mass selection is generally less than that could be achieved through pureline selection. It is because at least some of the plant progenies (= purelines ) that make up the new variety would be poorer than the best pureline that can be selected from among them. 3. In the absence of progeny test, it is not possible to determine if the selected plants are homozygous. Ever in self-pollinated species, some degree of cross-pollination does occur. Thus there is some chance that some of the selected plants may be heterozygous. It is also not known if the phenotypic superiority of the selected plants is due to the environment or the genotype. As suggested by Allard (1960), progeny test may be included in mass selection programmes to overcome this defect. 4. Due to the popularity of pureline varieties, mass selection is not commonly used in the improvement of self-pollinated crops. But it is a quick and convenient method of improving old local varieties in the areas or crop species where crop improvement has just begun. 5. Varieties developed by mass selection are more difficult to identify than purelines in seed certification programmes . 6. Mass selection utilizes the variability already present in a variety or population. Therefore, only those varieties/populations that show genetic variation can be improved through mass selection. Thus mass selection is limited by the fact that it cannot generate variablility .

23. ACHIEVEMENTS Mass selection, in one form or the other, must have been used by the prehistoric man to develop the present-day crop species. The differentiation of cultivated species from the wild forms clearly shows the efficacy and the contribution of mass selection to crop improvement. Mass selection was extensively used by farmers and agriculturists for the improvement of self-pollinated crops before pureline selection came into practice. Subsequently, it was completely replaced by pureline selection as a method of crop improvement. At present, the use of mass selection is limited to the purification of pureline varieties of self-pollinated crops. Mass selection is routinely practised every year or every few years to maintain the purity of pureline varieties. The contribution of mass selection in this regard would become much more obvious when one considers that pureline varieties tend to become genetically variable in a few years due to mechanical mixture, mutation etc. Thus the superiority of purelines would be lost quickly if their purity was not maintained through mass selection. All the available pureline varieties in self-pollinated crops are maintained through mass selection and their nucleus seed is, as a rule, produced through a process of mass selection.

24. Pureline Selection Mass Selection The new variety is a pureline . The new variety is a mixture of purelines The new variety is highly uniform. In fact, the variation present within a pureline variety is purely environmental. The variety has genetic variation for quantitative characters, although it would be relatively uniform in general appearance. The selected plants are subjected to progeny test. Progeny test is generally not carried out. Generally, a pureline variety is expected to have a narrower adaptation and lower stability in performance than a mixture of purelines . Usually the variety has a wider adaptation and greater stability than a pureline variety. The plants are selected for their desirability. It is not necessary that they should have a similar phenotype. The selected plants have to be similar in phenotype since their seeds are mixed to make up the new variety. . Generally, 7-8 years are required to develop a new variety. Generally, 6-7 years are required to develop a new variety.

25. References :- Book – Plant breeding : Principles and Methods https://www.google.co.in/search?q=pureline +selection+procedure&sca

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