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Mass Selection, , , , 14.1. INTRODUCTION, , , , , In mass selection, a large'number of plants ogSimilarphenoty ejarerselected and theirsseedscare, “, mixed»together to consiti iety. Selection is usually done for easily observable, , characters like plant height, ear type, grain colour; grain size, disease resistance, tillering ability,, lodging resistance, shattering resistance, etc. Sometimes yield may also be used as a criterion of, selection. If the population has variation for grain characteristics like seed colour and seed size,, selection may be done for them before the seeds of selected plants are mixed together. Generally,, , ti lants-are*not-subjectedst t, butrAllard:(1960):maintains»thateprogeny ,~—, testshould In such a case, poor and defective progenies are rejected, while the remaining, , progenies are mixed together to constitute the new population/variety., , i ined-from-selected.plants»wouldebe=more»uniformsthan..the. original, , population, particularly for easily observable characters Tike plant height, seed colour, presence, “OF awns, etc., which are governed by one or few, major genes. However, .the:population-is:likely, to:show.considerable-variation for-quantitative:characteristics'like:yield, quality, adaptability, etc. “~”, , The original population would have been a mixture of several purelines, and the plants selected, , from it would be homozygous. Since s, , , , everal plants are’selected and their seeds are mixed, the, , , , , , , , , , , mo, , selected population would be a mixture of several similar looking purelines. Thus a.variety, eveloped. throug tion WOULA NAVEs€ 1D eran” nd, cons€quently,, , 14.2, APPLICATIONS OF MASS SELECTION, In self-pollinated crops; mass selection has two major. applications: (Af improvement-of:desi- or, local’variétiés, and FB purification-of-thevexistingpurelinesvarieties,, , 14.2.1. Improvement, of Local Varieties } (, , Mass selection is useful for the improvement of desi or local varieties»o! f-self=pollin ated» crops., The 4 es, which may differ in flowering and/or, Re os acim eae, , Scanned with CamScanner
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223. Plant Breeding : Principles and Methog,, - |, , Maturity time, disease resistance, plant height, etc. Many of these plant types would be infer,, , and low yielding, and would lower the performance éf the local variety. ee |, plant types would improve the performance and uniformit of the variety. The loca Varieties,, , So oe, have been under cultivation for a long time. Therefore, the} would generat well adaptedj,, the local environment and would be relatively stable in their performance. ‘ViaSS'se" naWouly, , improve the local variety-witho “affecting ats-adaptability-and stabilitysbecause jy, new variety’ would-be made up of most of the superior p' anttypes presentinsthe original.varigyy, 14.2.2. Purification of Existing Pureline Varieties aa, , Purelines tend to become variable with time due to mechanical mixture, natural hybridization ang, , Mutation, Therefore, ureline..varieties=has-to=besmaintained “through=regularsma,, selection. As a rule, nucleus:seed:of -pureline -varieties*is:produced:through“mass*selection”, , As a breeding method, mass selection has: only limited application for improvement Of self., pollinated crops. It is generally:-not-used:for-handling:of»segregating «populations fromecrosses,, shei ee ed»foreselection;or<d, , desitablectraits. But this application is limited to such,, , , , gheitehas_b, , , , "Sifiarasters, fr which mass selection is rather easy and avoids extensive data collection needed, for single plant selection, e.g., for days to maturity, seed size, etc. However, |, species,mass.selection»has*been=quite-important-since inethissmethod»inbreeding-is-avoided ar, keptito.aiminimum. Further, because:of the-heterozygous:natu 0 se, , : : ae, , 14.3. PROCEDURE OF MASS SELECTION : é, The general procedure of mass selection for developing a new variety is outlined below Fig., 14.1). This procedure may be modified by the breeder according to the needs of his programme., 1. First Year. A large-number of ‘phenotypically-similar:plants:are-selected for vigour, plant, type, disease resistance and other desirable characteristics. The number of selected plants may, ; very from few-hundred.to.few..thousand..Jf too many plants are selected, the improvement is), likely to be small. But if:too-fewsplants-are-selected;-the-adaptation..of.the.variety.may becom, , poor. Seeds. from:the»selected»plants"are"composited to’ raise-the-next»generation. ae, , 2. Second Year. The.composited-seed.is.planted in a preliminary-yield: trial along-wit, 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 Phenotypi¢, , characteristics of.the-new-variety-arecritically~observed. j, 3. Third to Fifth Years. ‘The pesformance of new lines is evaluated in coordinated yield, trails at several locations within an agroclimatic zone and compared with that of the populat, varietigs used as checks. The new line is evaluated in an initial evaluation trial for one yeat-*, the line 1s promising; it is promoted to uniform regional trials for two or more years. If four, promising, the new line will then be identified for release as a new variety. “), , i: 4. Seventh Year. The new line may be released as a new. variety for cultivation if four!, suitable and if recommended by the competent variety release committee. | é, , In a variation of mass selection schem Fi : ts:arech arvest, of ms ig. 14.2) selected-plan tedsseparate!, Insthe:second:year, in i n, and-poors fective progel”, , areerejected. Progenies.from-heterozygous:plants:are-also-discarded. Care a noel?, “discard more than 20.25 percent ofthe progeties. Seed Homecare, , , , , , Scanned with CamsScanner
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Mass Selection, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , 223, 20900000]. : :, FIRST 20000000 (i) From a variable population, 200-2,000 plants, YEAR 20000000 With, Sitar but desirable traits are selected, 20000000|: _ {li) Seed fromthé selected'plants are composited, = —————<—<<_ oo, Yv (i) The composited seed is planted in a, SECOND Preliminary yield trial alongwith standard, YEAR _ checks, (ii) Phenotype of the selected population is, y critically evaluated, THIRD TO —f- (i) Promising sélections are evaluated in. ™, FIFTH YEARS _. €gordinated yield trails at several locations, (ii) Released as a new variety if it is superior to, the check variety., , , , , , y ., 90000000, , SIXTH e0000000) Oe oo, YEAR e0000000| .- Seed multiplication for distribution, , 90000000, , , , , , , , , , Fig. 14.1. Mass selection in self-pollinated crops for developing new varieties., , together,to.make-up'the new.variety. Insthe:third-and fourth years, the:variety:is:subjected:toryield, thals-in:-differentzenvironments. Since.the-selected.population: would=retain’ theadaptation of, original ‘variety, with-a-superior-performance, prolonged"testing*may-not*be=necessary. 3, This variation of mass selection is also used for the purification of existing pureline varieties., In the first year, a large number of plants typical for the variety are selected and’ harvested, separately from the pureline to be purified. In the second year, progenies from the selected plants, are grown and observed critically. Progenies;:whichyare'different from:the'ty pical*features:of the, concemed=varietyare* rejected The -remaining»progenies»are=mixed=together=toxconstitute“the, concemed* variety. This*processmay.-be-repeated.every:-fewsyears or as often as, it is found, necessary to keep the variety pure. This procedure is followed to produce the basic seed of, , pureline varieties; this seed ice nnn., , 14.4. MERITS OF MASS SELECTION, 1. Since a large number-of plants:are:selected, tipsadaptationsettiveseripinlassiciyeinenct, 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, varietiesdevelopedsthrough-mass”selection-are:likely:to-be-miore Widely adapted than,, , individualepurelites., 2. Oftenvextensive and prolonged:yield trails:are-notmecessary. This:reduces-the:time-and, _, , costaneeded.for.developing-themewsvariety., 3. Mass-selection*rétains»considerable: genetic.variability. in-the new*variety. Therefore,, a cE a gethe, varietyefurther., 4. It is a less demanding method so ha breeders can devicte more time to other breeding, programmes. :, , , , Scanned with CamScanner
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ra 7, , , , , , , , , , , , , , oe plant Breeding : Principles and Methog,, 224 Sf., i *, de 00000000 (i) Selest 200-2,000 plants of similar but superior, ie FIRST 00000000 henotype :, fe YEAR 00000000) tee (ii) Hariest seeds separately from each selected plant a, i. 00000000 i, 4 : ies, ; as ai, ‘ 2 (i) Grow individual plant proge ., c ii ject i ting. progenies, SECOND ii) Reject inferior or segregating Pf s, ‘vear {III HITT bs a Bulk the seeds from remaining progenies, , , , on fm, oa oe : LUGE ‘, , — R BGRE, , 00000000, SEVENTH |0 0000000, YEAR |00000000, 00000000}., , (i). Preliminary yield trail from the bulked. seed;, , standard checks are included wa, (ii) If superior, the new line is included in multilocation :, , yield trials, , (i) _Multilocation coordinated yield trials ee., “(ii) If superior to the check variety, released as a > new variety i é 5 :, , , , , , Seed multiplication for distribution to farmers, , See ee ce, , , , , , , , , , Fig. 14.2. Mass selection in self-pollinated crops coupled with progeny test. This method is more ‘useful, thin the one outlined. belore. It is commonly used for maintaining the purity of pureline, varieties and to produce their-basic or nucleus»seed (steps of year 1 and 2 only). « “, , 14.5: DEMERITS OF MASS SELECTION, , 1. The varieties:developed.through-mass:selection’show>variation and are*notias.uniform, as»pureline..varieties. Therefore, such varieties are generally less liked than pureline, varieties. :, , | 2. The improvement through’ mass:selection-is:generally Jess:than:thatscould»besachieved, , throughpureline,,selection. This is pecause at least some of the plant progenies, (= purelines) making up the new variety would be poorer than. the best pureline present, , . in the new variety., na: In:the:absence:of progeny. test, it isnotpossible to:determine.if-the. selected’ plantsyare, homoaysous. ay) a self-pollinated species, some degree of cross-pollination does, occur, ‘and some of the selected plants may be heterozygous. It.is,also.n mifithe, i ~..- phenotypic:superiority*of*the*selected. plants ‘cilidinaigeae aa Sait, | Progeny-test-may-be-included-in-mass.selection-programitieS'to overcome thie defect, 4. Duesto-the popularity-of. pureline. varieties, mass-seléction:is:not:commonly.used fot, improve! i it i i, mp! ps. But it is a quick and convenient methods of, , improving old local varieties in the area: :, A : 8 OF crop species wl i as, just begun. . Disp here crop improvement hi, , 5. Narietes developed by-mass selection ae more difficult to identify than pureline varie, , , , in»seed*certification:programmes,, , Scanned with CamScanner
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4g. ACHIEVEMENTS, , Mass selection, in one form or the other, must have been used b, , develop the present-day crop species.-The differentiation of cultivated species from the wild, forms clearly shows the efficacy and the contribution of mass sel, , 1 é ection to crop improvement., Mass selection was extensively used by farmers and agriculturists, , y the prehistoric humans to, , f, s before it was completely replaced by pureline selection. At present, its use is, limited to the purification of pureline varieties and, , production of their nucleus seed. This is a, valuable contribution of mass selection since pureline varieties tend to become genetically variable, with time. As a result, the superiority of purelines would be lost quickly if their purity were not, maintained through: mass selection. :, , Scanned with CamScanner
