modul 3. konsep dan metode seleksi

8/3/2019 Modul 3. Konsep Dan Metode Seleksi

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Konsep &Metode

Seleksi



• Pengertian seleksi• kegunaan seleksi

• syarat populasi yangdiseleksi• parameter genetik:

VariabilitasHeritabilitasKemajuan genetik

Content:



Pengertian seleksi



• Seleksi telah dilakukan sejak manusiamelakukan bididaya tanaman

• seleksi merupakan salah satuprosedur Pemuliaan Tanaman tertuauntuk perbaikan semua tanaman

• “Seleksi merupakan kegiatan untukmemisahkan individu atau kelompoktanaman dari suatu populasi tanaman “.

Pengertian seleksi



Seleksi dapat terjadi secaraalami atau secara buatan

(yang dilakukan olehmanusia).

Seleksi alami merupakan

proses dari evolusi, dimanaindividu yang kuat akanterus hidup sedang yanglemah akan hilang.

Seleksi buatan, yaitu seleksi yangsengaja dilakukan dan terarahpada tujuan yang ditentukan.



Seleksi buatan merupakan kegiatan yang meliputidua langkah penting,yaitu :• Memisahkan populasi untuk tetua-tetua

terseleksi (terpilih / yang akan digunakan) danindividu-individu tanaman yang tidakterpilih /dibuang)

• Reproduksi tetua terpilih untuk membentukpopulasi baru dengan cara :

1. Sumbangan tiap tetua terpilih keketurunannya pada generasi berikutnya.

2. Sistem persilangan/hibridisasi yangdilakukan bisa persilangan acak atau

sedarah.



Pemulia dapat melakukan seleksi yangefektif bila populasi mempunyavariabilitas yang luas, maka kemajuangenetic seleksinya aka cepat tercapai.

Selain itu juga apakah karakter-karakter yang diseleksi tersebutmudah diwariskan ke generasiberikutnya, untuk mengetahuinya perlu

diketahui nilai duga heritabilitasnya.



VARIATION AND ITS

USE

VARIATION AND ITS

USE

• Genetic variability

• Environmental variation• Variation caused by man• Racial variation• Mating system• Factors shaping variation• Selection



Basis for selection Especially on the economic traits

Must determine the amount, cause and thenature of variation

The variations in tree species are generally high Strategy for survival Long life Expose to various environmental condition

Giving more opportunity for selection Basis of variation

At cell level >>>>>> Chromosomes and gene



Causes and kinds of variability

Basically the differences among plant resulted from

i. The differing environments in which the plants aregrowing

ii. The genetic differences among plantsiii.The interaction between the plants gene types andenvironment in which they grow

P = G + E + GxE

G = geneticE= environmentGxE = interaction between G&E



Environmental variationSoil >> Light >> H2O >> Space

Effect on plant – competition among plants.

Factors can be controlled in Silviculturalpractices



Why is genetic variationimportant?

variation

no variation

EXTINCTION!!

globalwarming survival




variation

no variation

no r t h

s o u t h

nor t h

s o u t h




variation

no variation

divergence

NO DIVERGENCE!!

no r t h

s o u t h

nor t h

s o u t h



Genetic variation = additive gene action + non-additive gene action

σ 2

P = σ 2

G + σ 2

E

σ 2G = σ 2GA + σ 2GNA

σ2P = σ 2GA + σ 2GNA + σ 2E

Additive gene action = cumulative effects of allgene loci influencing trait

Genetic Variability



Non-additive divided by two

i. Dominance – interaction of specific affectsat a gene locus

ii. Epitasis – interactions among gene loci

Most characteristics of economic importancecontrolled by additive gene action

Additive variance can be used in simple

selection. e.g. wood density, bolestraightness non- additive – e.g. growth rate

Pest resistance – both additive & non- additive



Immediate evolutionary potential of apopulation is determined by the

heritabilityheritability which is defined as theproportion of total phenotypicvariation due to additive geneticvariation or:

h2 = VA/VPh2 = VA/VP..

HeritabilityHeritability



Broad-sense heritability (H B ) is the

proportion of the phenotypic variability

that results from genetic differencesbetween individuals:

Narrow-sense heritability (H N

or h 2) is the

proportion of total phenotypic variation due toadditive genetic differences betweenindividuals:

= V A /(V A + V D +V I + V E )



Narrow-sense heritability (HN or h 2) is

the key measure of genetic variation thatdetermines how much evolution occursduring selection.



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modul 3. konsep dan metode seleksi

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