CYTOGENETICS OF SORGHUM- crop botany and details of individual chromosomes

Chromosomal architecture of Sorghum

1. University Of Agricultural Sciences , Bangalore College of Agriculture, Bangalore CYTOGENETICS OF SORGHUM SUBHASHCHANDRA L. SHABANNAVAR PAMB3177 Jr. M.Sc. Agriculture Department of Genetics and Plant Breeding Exploring The Chromosomal Architecture of Sorghum CYTOGENETICS OF SORGHUM 1

2. Botanical name: Sorghum bicolor L. Moench Origin: Ethiopia Common name: Camel crop Chromosome no: 2n=2x=20 Seed (fruit type): grain (caryopsis ) Sorghum is the fifth most important cereal crop in the world after wheat, maize, rice, and barley . Sorghum is cultivated for grain and as a major food crop in much of South Asia, Africa, and Central USA. Sorghum is used for food, fodder, and the production of alcoholic beverages. It is a short day C4 plant . Sorghum requires warm climate , can tolerate high temperatures throughout their life-cycle better than any other crop . It can tolerate drought conditions very well because it remains dormant during moisture stress conditions but resumes growth when favourable conditions reappear . It can also tolerate water logging conditions better than any other cereal except rice. I ntroductio n CYTOGENETICS OF SORGHUM 2

3. Sorghum BOTANY •The stem is erect with leaves alternating on Opposite sides on nodes. Basal tillers are formed at the first node . • No. Of leaves range from 7-28 . The leaves have drought tolerance because of :- ➤ Small size of stomata cells during drought . ➤ A waxy layer which limits water loss . ➤ Presence of motor cells which cause rolling of leaves under drought stress CYTOGENETICS OF SORGHUM 3

4. •Inflorescence is raceme type(Panicle). • The panicle varies from being very loose to compact. •The panicle consists of spikelets which occurs in pairs. One spikelet is sessile, hermaphrodite & fertile. Other spikelet is pedicellate , male & sterile. panicle morphology is an important criterion for the racial classification of sorghum- guinea, caudatum , kafir and durra INFLORESCENCE CYTOGENETICS OF SORGHUM 4

5. SESSILE SPIKELETS The sessile spikelet has 2 glumes with lemma, 2 florets and Palea . Upper floret is complete. Lower floret is incomplete. Two lodicles are present adjacent to fertile lemma. Stamens : 3 Pistil : an ovary with two long styles with a feathery stigma PEDICELLATE SPIKELETS Two leathery boat shaped glumes enclosing 2 florets . The lower floret is represented by lemma & upper floret is staminate with short awned lemma . Palea : absent Stamens : 3 Pistil: Absent Sessile spikelet Pedicellate spikelet CYTOGENETICS OF SORGHUM 5

6. Common wild sorghum : Sorghum bicolor ssp. arundinaceum Grain sorghum : Sorghum bicolor ssp . bicolor The genus consists of 25 species and has been split into five sections : Eu-Sorghum,Chaetosorghum , Heterosorghum , Para-Sorghum , and Stiposorghum . Cultivated Sorghum is divided into five distinct races, namely:Bicolor , Caudatum , Guinea, Durra, Kafir CYTOGENETICS OF SORGHUM 6

7. Harlan (1972): proposed three sources of Gene pools : Primary gene pool (GP1) - includes cultivated sorghum (S. bicolor ssp. bicolor) and their wild & weedy relatives (S. bicolor ssp. arundinaceum , 2n=20 ). Secondary gene pool (GP2) - includes S. halepense with its tetraploid races halepense , miliaceum , Johnson grass etc Tertiary gene pool(GP3) - includes Saccharum , Sorghastrum , Miscanthus and related species . CYTOGENETICS OF SORGHUM 7

8. Cultivated species: Sorghum halepense (2n=4x=40) (Johnson grass) It is perennial, tetraploid and having rhizomatous root. It is wild weedy type It is distributed in eastern parts of India and Burma. ii ) Sorghum propingum (2n=2x=20 ) It is also perennial, diploid and having rhizomatous roots . iii ) Sorghum bicolor ( 2n=2x=20) It is annual, diploid and having fibrous root system . Three Subspecies : S . bicolor ssp. bicolor - cultivated & annual ii) S. bicolor ssp. Drammandi iiii ) S. bicolor ssp. verticilliflorum CYTOGENETICS OF SORGHUM 8

9. Sorghum halepense Sorghum propingum Sorghum bicolor Three cultivated species of Sorghum CYTOGENETICS OF SORGHUM 9

10. Table.01: CULTIVATED SPECIES OF SORGHUM CYTOGENETICS OF SORGHUM 10

11. Idiograms of seven different species of Sorghum CYTOGENETICS OF SORGHUM 11

12. Brief information on Individual Chromosomes of Genus Sorghum Chromosome I was the longest and chromosome X was the shortest . Chromosome I This longest chromosome of the complement is associated with the nucleolus- the nucleolus organizing region being situated very close to centromere region on the short arm . The Nucleolar Organising Region is spherical in shape and distinctly greater in diameter. Another characteristic feature of this chromosome is the presence of a deep staining chromomere terminating the heavily stained region in the long arm. 2. Chromosome II The chief feature which proved most useful in the identification of this chromosome is that the long arm is approximately twice the length of the short arm . The heavily stained parts in both arms show an abrupt transition to the lightly stained zones. The heavily stained region in the long arm is slightly greater than that in the short arm. CYTOGENETICS OF SORGHUM 12

13. 3. Chromosome III This is difficult to distinguish from the succeeding chromosome particularly in nuclei where it cannot be followed from end to end, due to the fact that both of them come close to one another in length. 4. Chromosome IV Identification of this chromosome on the basis of length alone is difficult for the reasons already mentioned under chromosome 3 . The deeply stained chromomere terminating the heavily stained segment, in the long arm and the of four small chromomeres in the transition region of the short arm capable of being well stained together form a reliable diagnostic basis 5. Chromosome V This is marked by the presence of a series of three small chromomeres in the transition region in the short arm like that described under the preceding chromosome.

14. 6.Chromosome VI This is the easiest chromosome to identify in the complement due to the marked asymmetry of its arms . The long arm is about five times the length of the short arm . 7. Chromosome VII This is chiefly distinguished from the rest of the long chromosomes by the comparative short length of the lightly stained segment in the short arm . 8 . Chromosome VIII This is recognised from the rest of the complement by the nearly equal length of its arm s. CYTOGENETICS OF SORGHUM 14

15. 9. Chromosome IX (23.1 μ to 26.8 μ). The quick recognition of this chromosome among the short chromosomes of the complement is facilitated by the characteristic presence of two deeply stained chromomeres terminating the heavily stained region in either arm. 10. Chromosome X. This is the shortest chromosome of the complement measuring. The arm lengths in many of the nuclei analysed have been found to be approximately equal , although on an average a difference of more than three microns was found. CYTOGENETICS OF SORGHUM 15

16. Sequential FISH identifying each of the ten chromosomes in sorghum ( a) First round of FISH using MCP10 ( digoxigenin -red) and MCP9 (biotin-green) probes . ( b) Second round of FISH using MCP8 ( digoxigenin -red) and MCP7 (biotin-green) probes. ( c) Third round of FISH using MCP6 ( digoxigenin -red) and MCP5 (biotin-green) probes. CYTOGENETICS OF SORGHUM 16

17. Interspecifc Hybridization Sorghum bicolor x S. halepense Ploidy groups and their derivation . Triploid Hybrids Most hybrids of sorghum х johnsongrass are expected to be triploid as normal haploid gametes for sorghum and johnsongrass would have n = x = 10 and n = 2x = 20 chromosomes, respectively, producing 2n = 3x = 30 progeny . Tetraploid hybrids Tetraploid hybrids of sorghum x johnsongrass likely result from the union of a 2n gamete of sorghum and a normal gamete of johnsongrass . Unreduced gametes can result from either pre- or post-meiotic chromosome doubling during mitosis, but have more commonly been a result of a restitution of the nuclear DNA during the first or second division of meiosis20. Because these hybrids are tetraploids , it is likely they are fertile and fully sexually compatible with johnsongrass . The other ploidy types observed among the progeny occurred at much lower frequencies. Hexaploid Hybrids The hexaploid progeny recovered in this study could result from a chromosome doubling of a triploid hybrid or the union of 2n gametes (2n = 2x = 20 and 2n = 4x = 40). CYTOGENETICS OF SORGHUM 17

18. Metaphase chromosome spreads for progeny of sorghum x Johnsongrass . Triploid 2n=3x=30 chromosomes; ( B) Tetraploid 2n=4x=40 chromosomes; ( C) Hexaploid 2n=6x=60 chromosomes. Scale bars are 10 µm. CYTOGENETICS OF SORGHUM 18

19. Tetraploid Sorghum Chromosome number 2n=4x=40 Tetraploid varieties of sorghum with larger vegetative organs than their diploid counterparts produce higher yield . On the other hand, with possible production of higher levels of sugar in these varieties, they will have more advantages for biofuel production . Nowadays , enhancement of biofuel production from plants is an important breeding objective in such plants. In this regard, production of polyploid varieties in plants such as sorghum could help to increase the production of biofuels . Therefore , in this experiment, we used an in vitro method for the doubling of chromosomes in sorghum bicolor for establishment of tetraploid plantlets. CYTOGENETICS OF SORGHUM 19

20. Thank you CYTOGENETICS OF SORGHUM 20