Plant Breeding Practices in Sorghum

Plant Breeding Practices in Sorghum

Cultivated Species:

A) Grain Sorghum: Sorghum bicolour L Moench ( 2n=20)
B) Forage Sorghum: Sorghum halpepense (2n=40)
                                    Sorghum Sudanese (2n=20)  

Sorghum bicolar (2n-2x-20) comes fifth after wheat, maize, rice, and barley in both area and production. It is one of the most important food crop in the semi and tropics of India, Africa. Australia, Argentina, mexico. In India it is cultivated on large scale in Maharashtra, Gujrat, Tamilnadu, Karnataka, Rajasthan and M.P.

Origin:

Sorghum is originated in Ethopia and South Asia. The progenitor of S. bicolar is sorghum arundinaceum ( 2n=20)

Based on inflorescence and spiklet morphology there is five major races i.e. Bicoalr, Guinea, Caudatum, Karir and Durra.

Botany:

Sorghum is annual/ perennial grass, the roots are adventitious and fibrous, stem is erect and made up of nodes and internodes, the pith may be sweet, juicy or dry. The leaves are 7 and 28 arranged alternating to opposite side with parallel venation. Presence of waxy layer limits the water loss. The panicle varies loose to compact, in some varieties panicle remain surrounded by sheath and some times penduncle recurred, giving pendent head referred as “goose neck”.

Panicle consists of spiklets in pairs; the sessile is hermaphrodite and fertile while other pedicillate is sterile. The sessile spiklet consists of inner and outer glumes enclosing two flowers, upper one is perfect and lower one is reduced. The perfect flower has thin narrow hairy lemma and small pelia enclosing three stamen, two lodicules and bifurcated feathery (brush like) stigma. The pedicillate flower is without pelia and ovary.

Grain is caryopsis, endosperm is starchy, and embryo consists of plumule, coleoptiles, radical coleorhizae referred as scutelum. Sorghum is breedable with S. halpense and also with sugarcane.
Floral biology and crossing. The flowering occurs prior to sunrise and extended up to mid- day, the blooming starts from tip of the panicle in downward direction. The stigma is receptive before flowering and remains receptive for 6 to 8 days. Pollens are viable for few hours and fertilization is completed with in 2 to 4 hours of pollination, jawar is normally self pollinated crop but stigmas exposed before dehisce lead to 6 to 30% cross pollination. The glumes open due to swelling of lodicules and another come out stigma. The stigma remains receptive for 8 to 16 days after blooming.

Emasculation:

A) Hand Emasculation:

Only the part of the penduncle is emasculated. Flowered tips and lower branches are removed by clipping. About 50 florets that would flower on next day are selected and emasculated and covered with suitable paper bag.

B) Hot Water Method:

In this method the sorghum head is immersed in water at 45 0 to 48 0C for 10 minutes, without injury to the stigma.

C) Plastic Bag Emasculation:
 
Sorghum heads are covered with plastic bag ton create high humidity in side the bag. Under high humidity florets open, anther emerges, but shed no pollens and the anther removed easily by tapping.

Pollination:

Pollination is done on next day between 9 to 10 a.m. all flower come to bloom. Inserting and shading the head in the bag collect the pollen. Another technique is clipping the heads early in the morning and placed in the boxes to flower in protected place. The collected pollens are dusted over exposed stigma or the pollen producing head brushed over emasculated head.

Breeding Objective:

1) High grain and fodder yield.
2) Early maturity
3) Resistance to drought, low HCN content, leafy, sweet juicy fodder.
4) Resistance to disease- Blight, downy mildew, rust, smut, charcoal, etc.
5) Resistance to insect pests- Midge, stem borer and shoot fly, etc
6) Bread making quality.

Breeding Procedures:

1) Pure Line Selection:

In this method superior land races are selected from local uniform variety and grown as plant progenies in the next year. Uniform superior progenies harvested and bulked as improved strain for further evaluation. In varietal evaluation, if improved strain shows superiority over the existing variety , it is released for commercial cultivation on large scale. E.g 1) M-35-1, 2) Sel-3, 3) Yashda , 4) Maulee( RSLG-262).

2) Pedigree Method:

This method consists of hybridization between desirable complementary parental lines, followed by selection of superior plants, in the segregating generation, till homozygosity is achieved. i.e. F5-F6. The selected plants are bagged to prevent out crossing varieties developed by pedigree method are SPV-86 ( R-24 X R-16), SPV-504 (Swati) (SPV 86 X M-35-1), CSV -15 R, ( SPV-475 X SPV-462)

3) Back Cross Breeding:

It is used to transfer one or few inherited traits from donor to another desirable genotype ( recipient parent) resistance to disease like grain mold, downy mildew, rust, smut, and resistance to insect pest like midge, shoot fly, stem borer could be introduced  in desirable strain by back cross breeding. Similarly cytoplasmic genetic male sterility could also be introduced by this method.

4) Hybrid Breeding:

Seeds of hybrid sorghum are produced using cytoplasmic genetic male sterility typically known as A, B and R line system. Kambine Kafir- 60 (m.s) was initial m.s line is used in hybrid seed production.

Male sterile line is known as A line its maintainer is known as B line. Line A and B are isogenic except that line A is male sterile line and B is male fertile. The difference lines only in cytoplasm, where line A has sterile cytoplasm ands line B has fertile cytoplasm. Any fertile line can be converted into male sterile by backcross breeding method.

A) Maintaince of A, B and R Lines:

A planting A and B line in 4:2 ratios in isolated field Maintaince male sterile line A. Seed produced on A line is male sterile. Line B is self fertile growing crop isolation or bagging the heads of B line plants, maintains B line. Similarly line R is also self fertile, is also multiplied by planting in isolated field.

In commercial seed production, i.e bulk production of A, B and R line is referred as foundation seed production and production of A X R referred as certified seed production. 

A Line (msms) X B Line ( msms) = A line (msms)

Male Sterile    X    Male Fertile    = Male Sterile  

A Line ( msms ) X R Line ( MsMs) = ( Msms) Hybrid Seed

Male sterile       X Male Fertile        = Male Fertile

New hybrids can be developed by improving performance of ‘A’ and ‘R’ lines or both by the back cross breeding method. Every year crossing programme of restorers with promising male sterile lines is undertaken and hybrids are tested for performance. If performance of particular hybrid found superior, it is multiplied on large scale for commercial cultivation. The popular hybrids are CSH-1, CSH-5, CSH-12, CSH-15 and CSH-16.

5) Resistance Breeding:

The resistance could be incorporated in given strain when desirable donor present is available by back cross breeding. Effective identification of donor and screening technique of mode of inheritance in needed, the characters controlled by recessive gene could easily be transferred by back cross breeding than character controlled by dominant genes. The important resistance source for pest and disease are given below.

A) Pest Resistance:

Shoofly:  IS-1034, 1054, 9136, 8314- Non preference for oviposition.
Stem Borer: IS-1054, 1034- Oviposition non preference
Midge: EC- 92792, DJ-6514, IS-18753 – Non Preference of host susceptibility is dominant.

B) Disease Resistance:

Head Mold: CSV-4, CSV-5, and SPV-35- incomplete dominant.
Downy Mildew: CSV-4, CSV-5, SPV-105, and CSH-5 – Resistance is recessive.     
Charcoal Rot: CSV -5, SPV-104,
Leaf Disease: 2219A, 2077A, CSH5, CSV-4, CSV-5, SPV-104, – Resistance is recessive.
Rust: 2219A, 296A, CS-3541, CSH-5, – Resistance is dominant.
The plant types have generally higher degree of resistance to foliar diseases.
 

Breeding for Striga Resistance:

Striga or Witch weed is an important root parasite on sorghum and other grasses. Strigol is stimulant produced by of host is required for germination of host. The resistance reaction includes low production of stimulant and mechanical barrier to haustorial penetration in the host plant.

Breeding for Forage Quality:

Sorghum is grown for grain and fodders the forage type varieties should high tonnage, more leafiness, juiciness, sweetness, good palatability and higher digestibility. Sorghum X Sudan grass is grown widely and has less problems of hydrocynic acid content (HCN).

International and National Programmes:

The international crop research institute of semi arid tropics (CRISAT) established in 1972 at Hyderabad as an international centre for improvement of grain yield and quality in sorghum. Sorghum variety ICSV-112 (SPV-475) released as CSV-13 for general cultivation in India. ICRISAT is working with collaboration of NRCS ( National Research Centre on Sorghum) at Nation level at Solapur for sacristy area.

Organized sorghum improvement programme in India startedinn 1962, when ICAR ( Indian Council of Agricultural Research) initiated accelerated hybrid improvement project. The project first tile release CSH-1 in 1964.

All India sorghum improvement project on sorghum was established in 1969 at Hyderabad involving ICAR and State Agricultural Universities. The project has involved hybrids and high yielding varieties at al India Level. In Maharashtra the project officer are doing research at following universities on various aspects.

1. Mahatma Phule Krishi Vidyapeeth, Rahuri.
2. Punjab Deshmukh Krishi Vidyapeeth, Akola.
3. Marathwada Krishi Vidyapeeth, Parbhani.

In Mahatma Phule Krishi Vidyapeeth research on sorghum is going on at Agricultural Research Station at Mohol (Dist Solapur) as lead center for Rabi Jowar and Agricultural Research Station Digras (Dist- Sangli) and Karad ( Dist – Satara) as testing centres for Kharif Jawar.