🌾 Botanical Description and Floral Biology

This lesson covers core principles and exam-focused points from this topic in plant breeding.

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Cereals

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Characters of Cereals

Most of the cereals are herbaceous annuals. Stem or culm often erect, cylindrical,

hollow except at nodes. Tillering habit, shallow fibrous root system . Leaves alternate,

distichously with parallel venation and sheathing leaf base . Presence of ligules, lodicules .

Inflorescence is panicle or spike . Stamens usually three (in rice - six) . Fruit is a caryopsis.

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Rice – _ Oryza sativa _ L. (2n = 24)

Systematic Position:

Division : Phanerogams

Sub-Division : Angeisperms

Class : Monocotyledon

Series : Glumacea

Sub class : Glumiflorae

Family : Poaceae

Sub family : Poaideae

Tribe : Oryzeae

Origin: India or Africa

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Putative parents and origin of cultivated rice

There are two divergent views regarding the origin of cultivated rice.

i. Polyphyletic: Originated from several species.

Acording to this theory, the two forms of cultivated rice viz., Asian rice O. sativa and

African rice, O.glaberrima have evolved independently in their respective regions from several

species.

ii. According to this theory both Asian rice and African rice arose from a common parent. ( O.

perennis ). This view is the most accepted one because both Asian rice and African rice are

similar except in glume pubesence, ligule size and colour of pericarp which is red in African rice.

Species in the genus Oryza

According to the latest view the genus oryza include 22 valid species. Out of these, two

are cultivated diploids viz. O. sativa and O. glaberrima and rest are wild species with include

both diploid and tetraploid forms.

Subspecies in cultivated Oryza savita

Rice has been in cultivation for long period and adapted well under diverse climatic

conditions and soils. This has resulted in the evolution of three geographical races which has

been given subspecies status. The three subspecies are:

i. O. sativa subsp indica : Tall spreading, more tillering, awnless

ii. O. sativa subsp japonia : Short, errect, more tillering, awnless

iii. O. sativa subsp javanica : Tallest, errect, poor tillering, awned

Marked sterility barriers occur between the subspecies. It ranges up to 80% in case of

indica x japonica where as it is less in case of indica x javanica.

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Wheat – _ Triticum sp _ . (X = 7)

Wheat is the most important cereal in the world, giving about one-third of the total

production, followed closely by rice. In temperate regions it is the major source of food. The

chief use of wheat is the flour for making bread.

Systematic position:

Division : Phanerogams

Sub-Division : Angeosperms

Class : Monocotyledon

Series : Glumacea

Sub class : Glumiflorae

Family : poaceae

Tribe : Triticeae

Subfamily : Pooideae

Chromosome number:

Diploid : 2n =14, Tetraploid : 2n = 28, Hexaploid : 2n = 42

Place of Origin:

Diploid: Asia minor, Tetraploid : Abyssinia, North Africa, Hexaploid : Central Asia

Classification:

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Ploidy level Species Common name Genome

Wild einkorn

Einkorn

Wild Emmer

Emmer

Macaroni wheat

Persian wheat

Rivet wheat

Polish wheat

Common or bread

wheat

Club wheat

Dwarf wheat

Spelt wheat

Macha wheat

AA

AA

AA BB

AA BB

AABB

AABB

AABB

AABBDD

AABBDD

AABBDD

AABBDD

AABBDD

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Diploid

(2n=14) 2 species

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Tetraploid

(2n=28) 7 species

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Hexaploid

(2n= 42) 5 species

T.boeticum

(T.aegilopoides)

T.monococum

T.dicoccoides

T.dicoccum

T.durum

T.persicum

T.turgidum

T.polonicum

T.timopheevi

T.aestivum

T.compactum

T.sphaerococcum

T.spelta

T.macha

Fourteen species of wheat are present according to Vavilov

1. T.boeoticum 2 .T.monococcum

3 .T.dicoccoides 4 .T.dicoccum

5 .T.durum 6.T.persicum

7 .T.turgidum 8 .T.polonicum

9 .T.timopheevi 10 .T.aestivum

11 .T.sphaerococcum 12 .T.compactum,

13. T.spelta 14 .T.macha.

Origin of diploid wheat:

(Wild einkorn) T.boeticum (T.aegilopoides )

Natural mutation and selection

T.monoccocum

Cultivated diploid

AA (2n = 14)

T. boeoticum is probably the ancestor for all the cultivated wheats

Origin of Tetraploid wheats: Origin of hexaploid wheats (Fig.2):

T.boeoticum x Aegilops spelltoides T.dicoccum x Aegilops squarrosa

AABB DD

AA BB 2n = 28 2n = 14

2n = 14 2n 14 F

ABD(2n = 21)

F

Sterile 1 [Sterile (2n=14) (AB) ]

Natural mutation and Doubling Natural doubling

T.dicoccoides 2n = 28 T.aestivum

Wild emmer AABB AABBDD (2n = 42)

By natural selection (Cultivated)

T.dicoccum (Emmer wheat)

AABB (2n=28) Cultivated

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Structure of Wheat Grain

Fruit is a dry, one seeded indehisent fruit known as caryopsis. The grain may be either

hard or soft in texture with a creamy white, amber, red or purple colour depending upon variety.

The dorsal (back side) convex surface of kernal is smooth except at the base where the fruit coat

is wrinkled indicating the position of embryo the ventral surface (front side) is flat and

charactersed by a deep furrow or groove.

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The following 4 structures are recognized in wheat grain

i.Grain coat, ii. Nucellar epidermis, iii. Endosperm and iv. Embryo.

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Summary Cheat Sheet

Quick Recall Points

• This lesson focuses on key plant breeding concepts, terminology, and exam-relevant applications.
• Review major definitions, classifications, and method-wise distinctions from the sections above.
• Revise tables and examples from this lesson for fast pre-exam recall.

Exam Traps

• Do not confuse similarly named breeding methods without checking their core selection logic.
• Pay attention to crop-specific examples because the same principle can behave differently by species.

References

1 source • [1]

[1]

Standard Plant Breeding Class Notes (GPBR211)

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