Hybridisation (7)

Question 1

To improve food crops breeders can _____ plants.

Answer 1

hybridise

Question 2

What are hybrid crops?

Answer 2

Hybrid crops are crops that are produced by cross-pollinating two inbred plants of dissimilar genotypes.

Question 3

What are the seeds from the cross-pollinated plant allowed to produce?

Answer 3

The seeds from this cross-pollinated plant are hybrid seeds and thus produce a ‘hybrid’ crop. As the crossing results in genetic variation the hybrid crop could exhibit new traits some of which could be desirable forming an improved crop or a new variety. If the plants were left as inbreds this would not have happened.

Question 4

True or false

GMO crops are the same hybrid crops.

Answer 4

False

Question 5

What improvements have been brought about by hybridisation?

Answer 5

• Plants are more vigorous.
• Improved disease resistance
• Earlier maturity and extended growing season
• Increased yield
• Quality improvement

Question 6

Why is hybridisation essential?

Answer 6

It is evident from this that plant breeding by hybridisation is vital for future agriculture as it enables farmers to progressively produce improved crop plants.

Question 7

What is a polyploid plant?

Answer 7

Polyploid plants are those containing more than two homologous sets of chromosomes, eg humans are diploid as they have two sets of homologous chromosomes.

Question 8

How can a polyploid plant develop?

Answer 8

A diploid plant can develop in to a polyploid by:
• a disturbance in mitosis or meiosis during crossing of two hybrids.
• its seeds being treating with the chemical, colchicine.

Question 9

Polyploidy is especially common in ____ plant species. Many genera and species have their origins in polyploidy

Answer 9

cultivated

Question 10

Advantages of polyploidy in agriculture (2)

Answer 10

1. Polyploidy forms seedless varieties of fruit such as watermelons, bananas, seedless grapes and some apples.
2. Compared to the diploid parents, polyploidy can make the:
   −plant bigger and more robust
   −flowers larger −fruitsbigger.

Question 11

What is mutagenesis?

Answer 11

Mutagenesis is an important tool in crop improvement and is free of the regulatory restrictions imposed on genetically modified organisms.

Question 12

What is mutation breeding?

Answer 12

Mutation breeding(sometimes referred to as ‘variation breeding’) is the process of exposing seeds to mutagens (chemicals or radiation) in order to generate mutants with desirable traits, e.g. larger seeds or sweeter fruits that are not found in nature.

Question 13

Plants created using mutagenesis are sometimes called ____ plants or ____ seeds.

Answer 13

mutagenic

mutagenic

Question 14

Currently there are over 1 000 mutant ____ of major staple crops being grown worldwide. Though poorly known, mutagenesis has produced thousands of useful ____ and make up a sizable fraction of the world’s crops including varieties of maize (711 lines), rice (534 lines), wheat (205 lines), barley, pears, peas, cotton, peppermint, sunflowers, peanuts, grapefruit, sesame, bananas, cassava and sorghum.

Answer 14

cultivars

mutants

Question 15

What is the use of mutagenesis for?

Answer 15

The use of mutagenesis to create novel variation is particularly valuable in those crops with restricted genetic variability.