Guava
is propagated by seeds or by vegetative means. The usual practice is tosow the
seeds immediately after extraction. Air layering is the most popular and
commercial .method of vegetative propagation. In recent years various
experiments have suggested that growth regulators were helpful in root
stimulation. Guava seeds have a hard coat which require longer time for
germination and number of seeds fail to germinate under traditional method of
raising root-stock. Physical treatment and use of certain chemicals or PGR's
have been found to be helpful in enhancing per cent germination of guava seeds.
Treatments of guava seeds with 5,000ppm ethephon resulted in 72 per cent
germination and yielded plants with longer shoots and more laterals (Sinha et
aI., 1973). Rodriguez et al. (1983) obtained more than 90 per cent germination
by soaking the seeds in water for 4 days followed by treating with GA3 (1000
ppm) for 24 hours. Looney (1998) reported that some PGR's have been helpful in
germination of guava seeds by increasing water uptake and exerting an effect on
membrane permeability. These results indicate that use of plant growth
regulator might have helped to break the embryo dormancy and induction of
synthesis of d-amylase and other hydrolytic enzymes.
Hardwood,
semi-hard wood and softwood stem cuttings can be used for propagation of guava,
clonally under mist conditions. Stem cuttiJlg are normally difficult to root
but varying degree of success has been obtained under different conditions and
with certain growth regulator treatment. Singh (1950) reported 77.7 per cent
success with hardwood cuttings of guava aftertreating with Hortomone A. Teaotia
and Pandey (1961) reported that both NAA (50ppm) and IAA (100 ppm) and 100 ppm
were more effective on semi-hardwood cuttings. Blommaert (1958) recorded 75 to
90 per cent rooting with softwood cuttings under intermittent mist along with
IBA treatment.
Jolicoeur
(1962) reported that treatment with 0.8 percent IBA in talc showed 44 per cent
rooting under mist. Bose and Mandai (1972) reported that the cuttings of guava
rooted betterunder mist and rooting was further e'1hanced by using IBA. Reddy
and Majumder (1978) reported synergism of phenols and flavonoids with IBA in
root regeneration of guava cuttings. Sadhu and Bose (1980) reported success in
the rooting of guava cuttings by pre-soaking treatment in ethephon (50 ppm) or
acetylene (100 ppm) followed by quick dip in 2,500 ppm of IBA orlAA. Treatment
with P-hydroxybenzoic acid (200 ppm) in combination with IBA (5,000 ppm)
recorded 93.3 per cent rooting in comparison with 60 per cent under contrQl
(Dhua et al., 1982a). Soft-wood cuttings with 2 nodes and 4 leaves rooted
better than semihard wood cutting when treated with 2000 ppm NAA (Pereira et
aI., 1983). Sen et al. (1967) also recorded 100 per cent rooting in the leafy
cuttings of guava under intermittent mist with treatment of IBA. Debnathand
Maiti (1990) also reported that IBA, NAA, IAA having 1500, 2500 and 3000 ppm
concentration respectively, significantly increased the percentage of rooting.
Sinha et al. (1962), Dhua et al. (1982b), Bhandari and Mukherjee (1969),
Pennock and Maldonado (1963) also reported similar findings.
Air-layering
is one of the most important comrnercial methods in practice for propagation of
guava. On account of the high population of mother plants per unit area, the
shoots remain juvenile for a long period, which affect the rooting ability of
shoots. Use of the bio-regulators have helped in overcoming this problem.
Higher success in air layers of the juvenile shoots was obtained with the
application of 30 ppm each of IBA and NAA mixture (Roa and Sulikeri, 1997).
Although NAA has higher potential for the rooting, it is not used singly as it
is toxic to the tissue, if used in higher concentration. According to
Sulladmath and Kololgi, (1969) NAA had synergistic effect on the rooting when
mixed with lBA formulation. Higher percentage of success in air layers by NAA
treatment was recorded by Chandra (1965). In Sudan, air layering proved to be the
best method of guava propagation followed by hard-wood cuttings treated with
IBA (Tingwa and Abhadi. 1968). Singh and Singh (1970) obtained the best result
on air layering of guava by using 2 per cent NAA. However, 3000 ppm IBA proved
veryeffecti'J€ in the rooting of air layer of cv. LA9 (Bhuibat.. 1972). All the
layers treated with NAA were found to produce roots (Singh, 1950). Equal
mixture of NAA and IBA at 10, 1000 ppm in talc produced the highest percent3ge
of rooting (Anonymous, 1961). Sharma 2t al. (1991) reported that 10,000 ppm IBA
increased success of air-layers and root quality in guava, Singh and Singh
(2001) also reported that 20,000 ppm of plant growth regulators (IAA, IBA and
NAA) was found optimum for better rooting. Sadhu et al. (1972), Tomar et al.
(1999), Bhagat et al. (1998) and (Chandrappa and Gowda, 1998) also reported
similar results.
Stool
layering is one of the most relevant technique for quick multiplication of
clonal root stock and scion cultivars on their own roots by heaping the normal
soil in the juvenile shoots resulting in induction of better root system, which
leads to higher degree of establishment under field conditions. Singh et al.
(1996) observed that 5000, 7500 and 10,000 ppm IBA significantly increased the
percentage of rooting and survival percentage in the stools of guava. Growth
regulators caused greater mobilization of sugars and nitrogenous substances,
which helped in the initiation of root primordia (Detweiler, 1942). Etiolated
plants were found to have a higher level of endogenous auxin (1M) at site of
etiolation (Kawase, 1965). Majumder and Mukherjee (1968) reported that IB A
induced more root in air layers. IBA (200 ppm) reduced the time for root
formation and increased the number of r09ts (Sharma et al., 1978). Application
of PBZ (2500 ppm) significantly increased rooting percentage, in stooling
(Singh, 1998). Profuse rooting in stools treated with auxins has been
considered to be on account of enhanced hydrolysis of nutritional reserves in
root formation. Effect of different auxins could be due to their respective
differences in initiating hydrolysis of nutritional reserves
(Bose, 1985). The tissue culture techniques is useful in rapid and mass
multiplication of plant materials. Micropropogation refers to regeneration of
plants from isolated maristemetic c€tls or tissues or from somatic cells.
Micropropogation can be used for rapid multiplication of crop plant which are
difficult to propagate sexualI~' or those vegetatively propagated species in
which rate or multiplication is slow (Singh, 1996). Similarly, studies on in
vitro propagation of Psidium guajava L. demonstrate that shoot tip ex-plant
from mature trees were capable of forming multiple shoot. Therefore, highest
number of shoots perex-plant were obtained from culture grown on MS medium
supplemented with 1 mg g'l BAP only (Jaiswal and Amin, 1987). The growth
hormones (auxins, cytokinins and gibberellins) are used for culture media
formation. The auxins are mainly used to facilitate cell division and root differentiation.
Commonly used auxins are IBA, NM, NOA, P-CPA, 2, 4-0 and 2, 4, 5-T. The IBA and
NAA are widely used for rooting (in combination with cytokinins) for shoot
proliferation. 2, 4-0 and 2, 4, 5-T are very effective for the induction and
growthof callus, and cytokinins or same as auxin. While GA3 is used to induce
plantlet formation from adventative embryo formed in culture (Gupta, 1997).
Similarly Ramirez Villalobos et al. (1998) reported that the cytokinins
(zeatin, zeatin riboside, kinetin, BA) is used to potential for development of
foliar primordia and leaves in vitro culture of leaf segments of guava.
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Horticulture