Plant Breeding Practices in Bajara (Pearl Millet)
Bajara ( Pennisetum americanum) (L)( 2n=14) is stable food in semiarid tropics. It is adapted for drought and poor soil fertility. In world the Bajara crop ranks sixth in importance followed by wheat, rice, maize, barley and jawar. India and Africa produce 92 % of world population. Bajara originated in Africa from where it was imported into India in the early days. The states growing bajara in large scale are Rajasthan, Gujarat, Maharashtra, Uttar Pradesh, Haryana and Punjab.
Origin:
Africa is considered to be centre of origin of bajara. The genetic name pennisutum is derived two Latin words Penna meaning feather and seta meaning bristles. The Pennisetum consist of six sub species as
1) P. ramosum ( 2n=10)
2) P. americanum ( 2n=14)
3) P. parpureaum ( 2n=28)
4) P. macsaicum ( 2n=16,32)
5) P.orientate ( 2n=18,36,54)
6) P.scuamalatum ( 2n=54)
Several wild species have been used in crosses with pearl millet.
Botany:
It is tall growing, and producing number of tillers. Roots are adventitious and fibrous; the stem is thin, round, greenish with nodes and internodes. Leaf sheath completely enriches the stem. The inflorescence is terminal, cylindrical and compact, spike having 10 to 50 cm length. Each spiklet consists of lower staminate and upper bisexual flower. The whorl consists of 30 to 40 bristles surrounded 2 to 5 spiklets. Each spikelet having two empty glumes and two inner glumes. The staminate flower is having single lemma and three stamens but does not have pelia and lodicules. The bisexual and hermaphrodite flower has broad lemma, three stamens, pelia, and single carpe, style dividing into two branches. The ovary is unilocular containing single seed.
Flowering and Crossing:
It is highly cross-pollinated crop due to protogynous nature. The style begins to appear 2 to 3 days after emergence of spike. First at 1/3 rd portion and gradually downward, and style remain receptive for 1 to 2 days. Anther emerge after styles dry up. The anthers of bisexual flower appear 2 to 3 day before those of staminate flowers. The maximum emergence of style is between 9.00 a.m to 3.99 p.m. while maximum opening of the flower occur between 10.00 a.m. to 2.00 p.m. and minimum between 3.00 and 6.00 p.m.
Selfing:
To ensure selfing spike may be bagged before emergence of the stigmas. Two full from same plant one a few days older than other and ready shed pollens could be bagged in the same bag for good seed. Generally spikes in several stages of anther can be found on the same time.
Emasculation:
Hand emasculation is laborious and difficult due to small size of flowers and the late development of anthers in relation to stigma. Protogynous nature of the flower suggests the easy method of crossing without emasculation. In the lowermost part of the ear head the styles appear very later. In the lowermost part of the ear head the styles appear very late. This interval between appearance of styles and dehiscence of anthers is more particularly in lowermost region of the spike. Hence the spike emerged from the flag leaf is selected for emasculation and upper 2/3 rd or 4/5 portion of ear head is cut and remaining portion of the head is bagged immediately.
Pollination:
It is always done in the morning after 2 to 3 days when styles appear, fresh pollen grains collected from protected male parent in petridish and dusted over the stigma of the bagged heads and rebagged immediately. The pollination may be repeated 2-3 times till the anthers of the same region show their appearance.
Breeding Objective:
1) High Grain Yield With
a. Well field compact head
b. More tillers
c. Bold grains and ripening uniformity
d. Earliness
e. Reduced plant height
f. Bristeled ear
2) High Forage Yield with Leafiness and Good Digestibility:
3) Resistance to Diseases:
a. Downy mildew – Resistance donor- Ex Bornue
b. Ergot-IP-517, IP-1956, IP-1533.
c. Drought resistance – J-1270
d. Fodder Quality : Napier- bajara hybrids E.g. K-677, D-1941.
Breeding Methods:
1) Mass Selection:
In this method desirable plants are selected from open pollinated population and the seed from selected plants composited and planted to initiate next cycle of selection. The criteria are usually head characteristics, like compactness, length of ear, weight of grain, uniformity of ripening etc. varieties developed- Jamnagar, Jaint, Pusa moti, etc.
2) Hybrid Breeding:
It includes development of inbreds through inbreeding and pure line selection, (J-88, J-104, K-560, K-559, etc) and adoption of cytoplasmic genetic male sterility under standard three line system (A, B, and R) to produce hybrid seed. CMS line ‘A’ is multiplied by planting it with maintainer line B in isolated field (1000m). Seed set on ‘A’ line is the male sterile. B and R lines are multiplied in isolated field separately. Desirable R line is crossed with A line to produce the F1 hybrid. The anthers of the pollinator ( R line) should coincide with exertions of stigma of A line and the R lines should provide pollens over long period to insure good seed setting.
Any fertile line can be sterilized and new male sterile can be developed by back cross breeding method. The performance of the hybrid is improved by improving performance of the hybrid is improved by improving performance of parent lines, i.e. A line, R line, or both.
Popular hybrids developed by cytoplasmic male sterility.
1. MH-179-821A X ICMP-451 (1987)
2. MH-169- 841A X D -23 (1988)
3. RHRBH- 8609 (Shradda) –RHRB-IA X RHRBI-138 (1990)
4. RHRBH -8924 (Saburi) – RHRBI-5A X RHRBI-458 (1995)
5. ICMH-451- 81 A X ICMP-451.
Population or Synthetics and Composites:
Synthetics are the populations that are synthesized by inter pollination among the high GCA lines. The synthetics are reconstituted at certain intervals by inter pollination among the component lines and therefore Maintaince of components lines is essential. E.g. ICMS-7703, ICMV-87901.
Composites are the populations produced by mixing seed of phenotypically outstanding lines and encouraging open pollination in isolated field. The components may be any number selected without testing combining ability. Reconstitution never done in composites varieties. E.g. WC-C-75, PSB-8, HC-4, RHR-1, ICTP-8203, etc.
Breeding for Disease Resistance:
1) Downey mildew – Ex Bornu (Resistance Source)
2) Ergot – IP-517, IP-1956, and IP-1533.
3) Drought Resistance: J-1270
Interspecific Hybrid:
The green fodder quality depends on more leaf number, thin stem, earliness and high tillering, protein, and mineral matters. On the other hand oxalic acid need to be minimum. The Interspecific hybrids between napier grass ( P. purpurium -4n) X bajara ( P. americanum- 2n ) are Napier bajara hybrids, the popular hybrids are Desharat and Yashawant famous for high yield. These are also known as elephant grass.