Everything you need to know about modes of reproduction and mating systems in crop plants !
Q. 1. What is reproduction?
Ans. The process by which living organisms give rise to the offspring of similar kind (species) is called reproduction.
In crop plants the mode of reproduction is of following two types:
(i) Asexual reproduction:
It refers to multiplication of plants without the fusion of male and female gametes. It is of two types, viz. vegetative reproduction and apomixis.
(ii) Sexual reproduction:
It refers to multiplication of plants through fertilized embryos.
Q. 2. What is vegetative reproduction?
Ans. Multiplication of plants by means of various vegetative plant parts such as stem cutting and root cuttings. It is of two types, viz. natural and artificial.
Q. 3. What is natural vegetative reproduction?
Ans. Multiplication of plants in nature by vegetative means is called natural vegetative reproduction. It may occur by underground stems, sub aerial stems, root and bulbs.
(i) Underground stems:
These are of four types, viz. Rhizomes, tuber, corm and bulb. Rhizomes are found in turmeric and ginger, tuber in potato, corm in Arvi and Bunda and bulb in garlic and onion.
(ii) Sub-aerial stems:
These groups include runner, sucker, stolen etc. and are found in mint, rose, strawberry, banana etc.
(iii) Bulbills:
These are modified form of flower and are found in garlic. They develop into plants when fall on the ground.
Q. 4. What is artificial vegetative reproduction?
Ans. Multiplication of plants by vegetative parts through artificial method is known as artificial vegetative reproduction. It occurs by stem cutting, root cutting, layering, grafting and gootee.
Q. 5. What are advantages of vegetative reproduction?
Ans. Advantages of vegetative reproduction are given below:
(i) It maintains genetic purity of a genotype generation after generation.
(ii) It is useful in mass multiplication of a genotype.
(iii) In plant breeding, desirable plants can be selected and maintained by vegetative reproduction.
(iv) Bud mutation can be directly released as new varieties.
Q. 6. How reproduction occurs in sugarcane, grapes and roses?
Ans. In sugarcane, grapes and roses reproduction occurs through stem cuttings.
Q. 7. How reproduction occurs in sweet potato, citrus and lemon?
Ans. In sweet potato, citrus and lemon, reproduction occurs by stem cuttings.
Q. 8. What is the main drawback of asexual reproduction?
Ans. The main drawback of asexual reproduction is that it does not allow combining of desirable genes from different sources.
Q. 9. What is amphimixis?
Ans. The union of male and female gametes is known as amplimixis.
Q. 10. Who coined the term amphimixis?
Ans. The term amphimixis was first used by Weismann in 1891.
Q. 11. What is the significance of sexual reproduction?
Ans. The importance of sexual reproduction is given below:
(i) It offers opportunities to combine desirable genes into a genotype from different sources.
(ii) It creates genetic variability by hybridization and crossing over. Crossing over takes place during meiosis and leads to new gene combinations. Crossing over does not take place in asexually propagated species.
Q. 12. What is autogamy?
Ans. Development of seed by self-pollination is known as autogamy; also called self-pollination.
Main features of autogamy are given below:
(i) It is the closest form of inbreeding.
(ii) It leads to homozygosity.
(iii) Autogamous species develop homozygous balance and do not exhibit significant inbreeding depression.
Q. 13. What are mechanisms which promote autogamy?
Ans. The following mechanisms promote autogamy:
(i) Presence of bisexual or hermaphrodite flowers (bisexuality)
(ii) Maturation of anthers and stigma of a flower at the same time. (Homogamy)
(iii) Pollination and fertilization in unopened flower bud (Cleistogamy)
(iv) Pollination immediately after flowering (Chasmogamy)
(v) Surrounding of stigma by anthers.
Q. 14. What is homogamy?
Ans. Maturation of anthers and stigma of a flower at the same time in called homogamy. As a rule, homogamy is essential for self-pollination.
Q. 15. What is cleistogamy?
Ans. Cleistogamy refers to pollination and fertilization in unopened flower bud, It ensures self-pollination and prevents cross pollination. It has been reported in some varieties of wheat, barley, oats and several other grass species.
Q. 16. What is chasmogamy?
Ans. In plants, fertilization after opening of flower is called chasmogamy. It promotes self-pollination and is found in wheat, barley, rice and oats.
Q. 17. What is bisexuality?
Ans. Presence of male and female organs in the same flower is known as bisexuality. All self-pollinated species have hermaphrodite flowers.
Q. 18. What is semigamy?
Ans. When male nucleus enters the egg cell but does not fuse with egg nucleus, it is known as semigamy.
Q. 19. Who coined the term semigamy?
Ans. The term semigamy was coined by Battaglia in 1963.
Q. 20. What is allogamy?
Ans. Development of seed by cross pollination is called allogamy.
Main features of allogamy are given below:
(i) It is the common form of outbreeding.
(ii) It leads to heterozygosity.
(iii) Allogamous species develop heterozygous balance and exhibit significant inbreeding depression on selfing.
Q. 21. What are mechanisms which promote allogamy?
Ans. The following mechanisms promote allogamy:
(i) Dictiny:
It refers to unisexual flowers.
(ii) Dichogamy:
It refers to maturation of anthers and stigma of the same flower at different times,
(iii) Heterostyly:
It refers to variation in the length of style and filaments in the same flower.
(iv) Herkogamy:
It refers to hindrance to self-pollination due to hyline membrane around the anther, and
(v) Presence of self-incompatibility and male sterility.
Q. 22. What is decliny?
Ans. Presence of unisexual flowers is called decliny.
It is of two types as follows:
(i) Monoecy:
It refers to separate presence of male and female flowers in the same plant. In some crops, male and female flowers are present in the same inflorescence such as mango, castor and banana. In some cases, they are on separate inflorescence such as in maize.
(ii) Dioecy:
It refers to presence of male and female flowers on different plants. It includes papaya, date palm, spinach, hemp and asparagus.
Q. 23. What is dichogamy?
Ans. Maturation of anthers and stigma of the same flower at different times is called dichogamy. It promotes cross pollination even in hermaphrodite species.
It is of following two types:
(i) Progogyny:
In this type, pistal matures before anthers such as in pearl millet.
(ii) Protandry:
In this type anthers mature before pistil such as in maize and sugar beet.
Q. 24. What is heterostyly?
Ans. Different lengths of styles and filaments in a flower refer to heterostyly. It promotes cross pollination such as in linseed.
Q. 25. What is herkogamy?
Ans. Hindrance to self-pollination due to some physical barriers such as presence of hyline membrane around anther is called herkogamy. Such membrane does not allow dehiscence of pollen and prevents self-pollination as in alfalfa.
Q. 26. What is anthesis?
Ans. The process of dehiscence of anthers or the period of pollen distribution is called anthesis.
Q. 27. What do you mean by in-breeders?
Ans. The self-pollinated plants are also known as autogamous plants or in-breeders.
Main features of in breeders are given below:
(i) They are self-pollinated
(ii) They are homozygous and true breeding
(iii) They have homozygous balance and are tolerant to inbreeding
(iv) New gene combination is not possible due to regular self-pollination.
(v) In-breeders are composed of several homozygous lines.
(vi) They have close adaptation.
(vii) They have more of additive gene action.
Q. 28. What are out-breeders?
Ans. Cross pollinated plants are also known as allogamous plants or out-breeders.
Main features of out-breeders are given below:
(i) Out-breeders hove random mating.
(ii) They are heterozygous and have advantage of heterozygosity.
(iii) They are intolerant to inbreeding.
(iv) They permit new gene combination due to cross pollination.
(v) They have wider adaptability.
(vi) They have more of non-additive gene action.
Q. 29. What effects of inbreeding are on cross pollinated species?
Ans. Main effects of inbreeding on cross pollinated species are given below:
(i) The homozygosity is increased due to fixation of genes.
(ii) The heterozygosity is reduced due to fixation of genes.
(iii) The population mean is reduced due to decrease in number of hybrid genotypes.
(iv) The genetic correlation increases between close relatives due to increase in prepotency, which increases with homozygosity.
(v) The hidden variability becomes free.
Q. 30. What are effects of out-breeding?
Ans. Main effects of out-breeding are given below:
(i) The heterozygosity is increased due to random mating,
(ii) The homozygosity is reduced because outbreeding favours heterozygotes.
(iii) The population mean will increase due to increase in heterozygosity and combining more dominant genes from different lines.
(iv) The genetic correlation will decrease due to decrease in homozygosity.
(v) The variability is increased due to inter-mating and segregation.
Q. 31. What is mating system?
Ans. The method by which individuals are paired for crossing is called mating system.
Q. 32. Who coined the term monoecious?
Ans. The term monoecious was coined by Darwin, in 1877.
Q. 33. Who termed the term heterostyly?
Ans. The term heterostyly was first used by Darwin in 1865.
Q. 34. Who first reported double fertilization?
Ans. Double fertilization was first reported by Navashin and Guignard in 1899.
Q. 35. Who gave systems of mating?
Ans. Systems of mating were given by Sewall Wright in 1921.
Q. 36. What are different systems of mating?
Ans. There are following five systems of mating:
(i) Random mating system
(ii) Genetic assortative mating
(iii) Genetic disassortative mating
(iv) Phenotypic assortative mating
(v) Phenotypic disassortative mating.
Q. 37. What is random mating?
Ans. A mating system in which each female gamete has equal chance to unite with every male gamete is called random mating.
Main features of random mating are given below:
(i) It is a form of outbreeding,
(ii) Without selection, variability, population mean and genetic correlation between relatives remain constant.
(iii) It is useful in development and maintenance of synthetic and composite varieties.
Q. 38. What is genetic assortative mating?
Ans. It refers to mating between genetically similar or closely related individuals.
Its main features are given below:
(i) It is commonly known as inbreeding.
(ii) It leads to increase in homozygosity, genetic correlation and variability among lines (without selection). It leads to reduction in heterozygosity and population mean.
(iii) It is useful for development of inbred lines.
Q. 39. What is genetic disassortative mating?
Ans. It refers to mating between genetically dissimilar individuals or between less closely related individuals.
Its main features are given below:
(i) It is commonly known as outbreeding,
(ii) It leads to increase in heterozygosity, variability and population mean, and decrease in homozygosity and genetic correlation.
(iii) It is useful in population improvement.
Q. 40. What is phenotypic assortative mating?
Ans. It refers to mating of extreme types, viz. AA x AA and aa x aa.
Its main features are given below:
(i) The variability is divided into two extreme types (AA and aa).
(ii) The population mean is divided according to variability.
(iii) It is useful (with selection) in development of extreme phenotypes.
Q. 41. What is phenotypic disassortative mating?
Ans. Mating between phenotypically dissimilar individuals (AA x aa) is called phenotypic disassortative mating.
Its main features are given below:
(i) It maintains genetic variability due to production of intermediate types.
(ii) Heterozygosity and population mean remain constant.
(iii) Genetic correlation between relatives decreases due to decrease in prepotency, which is decreased due to decrease in homozygosity.
(iv) This system is used in disruptive mating programs.
Q. 42. What is prepotency?
Ans. The property of an individual to produce progeny which are identical to each other and to the parent is called prepotency.
Q. 43. What is gamogamy?
Ans. Gamogamy refers to sexual reproduction.
Q. 44. Who coined the term gamogamy?
Ans. The term gamogamy was coined by Hartmann in 1904.
Q. 45. Give comparison of random, genetic assortative and genetic disassortative systems of mating.
Ans. Comparison of these systems of mating is presented below in table 4.1.
