Importance of Conventional Breeding Methods in plants

Author

Muhammad Abdullah Bin Masood

Importance of Conventional Breeding Methods in plants

PMAS Arid Agriculture University Rawalpindi

AbstractIn this article, I have written about concept of plant breeding, about plant breeders, conventional breeding methods, their importance & overview of modern breeding methods.

ContentsCONCEPT OF PLANT BREEDING............................................................................................................................ 2

PLANT BREEDERS..........................................................................................................................................................2

CONVENTIONAL BREEDING METHODS................................................................................................................. 2

SELECTION.......................................................................................................................................................... 3

HYBRIDIZATION.................................................................................................................................................. 3

TYPES OF HYBRID PLANTS...............................................................................................................................................4Inter-specific........................................................................................................................................................4Inter-generic........................................................................................................................................................4

HETEROSIS..................................................................................................................................................................4

POLYPLOIDY........................................................................................................................................................ 5

TYPES OF POLYPLOID.....................................................................................................................................................5Autopolyploid......................................................................................................................................................5Allopolyploid........................................................................................................................................................5Polyploid plants...................................................................................................................................................5

OVERVIEW OF MODERN BREEDING METHODS....................................................................................................6

MUTAGENESIS.............................................................................................................................................................6PROTOPLAST FUSION.....................................................................................................................................................6GENOME EDITING.........................................................................................................................................................6TRANSGENIC................................................................................................................................................................6

IMPORTANCE OF CONVENTIONAL PLANT BREEDING METHODS...........................................................................7

REFERENCES’....................................................................................................................................................... 8

Importance of Conventional Breeding Methods in plants

Concept of Plant Breeding “It is scientific and artistic discipline of agriculture that dart on enhancing the productive potential and food value of the crop varieties or cultivar either through classical or modernistic techniques for fulfilling the need of human population”

Plant breeders

For hundreds of centuries people are following traditional plant breeding techniques for enhancing the performance of crop cultivars. Many of the plant breeders have dedicated their entire life in enriching a particular variety or cultivar. Before the success of scientific knowledge they focused totally in selection of plants with good characters. They have bird’s eye view in selection of unique plants with in the same species. Through successful cross-pollination they have developed high yielding varieties of plants. A plant breeder named Luther Burbank; developed about 800 species of various fruits & vegetables through traditional plant breeding methods.

Conventional breeding methods

Plant breeding deals with the observance & selection of particular traits in plant and their incorporation in a single plant variety or cultivar. Conventional plant breeding deals with the exploitation of chromosome combination. There are usually three ways of exploiting this combination, these are; (BATS)

1. Selection

2. Hybridization3. Polyploidy

Selection

Very old method practiced in plant breeding. Generally it includes the following steps;

1. Selection of large number of plants from a genetically variable base population (introduction, segregating population through crosses & landraces)

2. Establishment of progeny rows from individually selected plants for assessment. After clear roughing, selected phenotypically superior plants are grown over years & years. This is done for allowing observation of performance under varied environmental conditions for further roughing.

3. Selected lines or varieties are subjected to yield trials in comparison with the existing ones for the assessment of their performance. (BATS)

Hybridization

It is the most consistently method practiced method in plant breeding. The aim of plant breeder is to incorporate desired traits from different lines in to a single plant line through crossing. In this method there are the following main steps;

1. Development of homozygous inbred lines, possibly through selfing.2. Out crossing with between desired homozygous inbred lines.3. Crossing with wild species for traits, such as, disease resistant, drought

tolerance etc. But demerit is that it requires frequent backcrossing with parent plants to remove undesired traits such as, low yield, low quality, bad taste, & toxic compounds etc. (BATS)

Types of hybrid plants

1. Inter-specific2. Inter-generic

Inter-specific

It is a type of hybrid plant that has been developed through crossing between parents have a common genus e.g. Triticum aestivum X Oryza sativa Inter-generic

It is a type of hybrid plant that has developed through crossing between parents from different genera e.g. x Ferobergia, an inter-generic hybrid between Ferocactus & Leuctembergia. (Intergeneric -hybrid)

Heterosis

It is an influence that is the consequence of crossing between two highly homozygous inbred lines. Whenever we move toward development homozygous inbred lines, their came a strong decrease in plant vigor & size in first generations however after 5th & 6th no more this phenomena happens. When such type of inbred lines are subjected to crossing with other inbred plants, highly vigorous, high yielding, wider adaptable & resistant plants may result. Although hybrid plants are high yielding and highly vigorous but there is a demerits that heterosis effect has been lost during hybridization with in the inbred parental lines so every year farmer have to buy new seed rather that relying on seed through yield. (BATS)

Polyploidy

It refers to phenomena of having more than 2 set of chromosomes. Usually plants are diploid but plants with more than 2 complete chromosomal set may also common. It has been thought that about 30-70 % angiospermic plants are polyploid. Polyploidy can be achieved artificially by the application

of colchicines, which result in chromosomal doubling. The main objective of polyploidy is increment in size & genetic variability but they are usually less fertile and slow growing type. (BATS)

Types of polyploid

There are two generally two types of polyploids

1. Autopolyploid2. Allopolyploid

Autopolyploid

It is an individual or strain having more than 2 set of chromosomes of a single ancestral plant species.

AAAA X AAAA = AAAA an autopolyploid

Allopolyploid

An allopolyploid is a plant species with a more than 2 chromosomal set of different plant species.

AAAA X BBBB = AABB an allopolyploid

Polyploid plants

Plant species Basic genome number

Chromosomal number

Polyploidy level

White potato 12 48 4n

Sugarcane 10 80 8n

Cotton 13 52 4n

Apple 17 34, 54 2n, 3n

Overview of modern breeding methods

Mutagenesis

In this method plants are subjected to mutagens or radioactivity in order to induce random mutations for the creation of desired traits e.g. darker red color of grape fruit is accomplished by this method (Mogel)

Protoplast fusion

In this method desired traits are transferred from one species to the other through fusion of cell or its components e.g. we have successfully created male sterility in red cabbage by fusion of cells between red Cabbage & raddish . (Mogel)

Genome editing

In this method various enzymes are used to modify DNA with in the cell e.g. canola resistant to herbicide has been developed by this method. (Mogel)

Modern plant breeding

Mutagenesis

Genome editing

Transgenics

Protoplast fusion

Transgenic

In this method desired genes are incorporated from one species to the other e.g. Rainbow papaya resistant to PRV or Papaya Ringspot virus has been developed by this method. (Mogel)

Importance of conventional plant breeding methods If we move toward 1960s then we see the peaks of conventional plant breeding methods. A well renowned term Green revolution, in which a scientist Norman Borlaug, developed high yielding and fertilizer responsive dwarf varieties of cereals through conventional methods and he was awarded Nobel prize on his this work. The science of plant breeding is getting more & more advanced but still they never supplant the importance & need of conventional breeding methods. Conventional breeding methods are always being the basic source of any plant breeding program. One can easily understand the need of conventional breeding methods. Suppose farmers want to have high yielding fruit variety, he will first select the plant with vigorous fruit size & weight, save its seed & sow them further he applies modern techniques for enhancing his research. In fact modern techniques promote the research work carried on plant through conventional methods. Monsanto said, “we spent about 50% of investment is done over conventional plant breeding system for foundation of breeding program”.(Monsanto) They provide a base line for enriching the protoplast. Fruits & vegetables that we eat today are not wild they have been modified through modern and traditional breeding methods. Crossing through conventional methods may result in combination of undesired traits and their removal is very time-consuming however modern methods will helps to overcome this problem and thus both methods favors each other. Maize plant that has been developed from teosinte to present-day corn is the achievement of traditional breeding methods and is further enriched through modern methods into BT Maize.

References’ BATS, A. (n.d.). Retrieved May 21, 2016, from BATS-center for biosafety & sustainability : http://www.bats.ch/bats/publikationen/1995-1_TA/2-methods.php

Intergeneric -hybrid. (n.d.). Retrieved May 21, 2016, from cactus-art.biz: http://www.cactus-art.biz/note-book/Dictionary/Dictionary_I/dictionary_intergeneric.htm

Mogel, K. H. (n.d.). biofortified.org. Retrieved May 21, 2016, from http://www.biofortified.org/2015/07/crop-modification-techniques-infographic/

Monsanto. (n.d.). Retrieved May 21, 2016, from discover.monsanto.com: http://discover.monsanto.com/plant-breeding