wider chances for selection of superior types whose characteristics are perpetuated through vegetative
propagation. Generally, the population thus obtained is a mixture of several clones. Each clone is het-
erozygous although homogeneous, and the same genotype is maintained because propagation is vegeta-
tive, Interclonal variations are due to heredity. Depending on climatic and soil conditions, different coun-
tries follow different modes of vegetative propagation. Hamada [63] described the methods used in Japan,
which include (1) bark grafting (Fukurotsugi), (2) veneer grafting (Kiritsugi), (3) simple layers (Mage-
dori), (4) continuous layers (Shumokudori), and (5) division (Shirodasmi), hardwood cuttings (Ko-
jyosashiki), and softwood cuttings (Shinshosashiki), Generally, grafting is used in places where the tem-
perature is 6°C in March and more than 25°C in July, with rainfall of 175 mm. Shirodasmi cottage is
popular in places having temperatures less than 4°C in March and less than 25°C in July with rainfall
lower than 175 mm. Propagation through hardwood and softwood cuttings is common in the northern dis-
tricts and the southern region, respectively, of Japan [64]. In Italy [65], rooted grafting is a popular method
of multiplying Japanese mulberry varieties.
In India, the most common method of propagating mulberry is through cuttings in multivoltine re-
gions (e.g., Karnataka and West Bengal). Exotic varieties that are not established by cuttings are propa-
gated through root grafts. Many of the indigenous varieties and well-acclimatized exotic varieties are
propagated through cuttings. Bud grafting (budding) is used only when scion material is scarce. When-
ever a large number of mulberry plants must be obtained in a shorter time than would be possible if they
were started as a cutting, the method of layering is used. Layering allows the grower to fill in the gaps
formed as a result of the failure to sprout of certain cuttings planted in pits of established plantations.
In univoltine areas (e.g., Kashmir), the mulberry is propagated through seedlings and the exotic va-
rieties through root grafts. In India, the field-scale propagation through cuttings of Japanese varieties of
mulberry is still a problem.
Propagation through seeds is used mainly to bring about a varied population for the purpose of se-
lection and hybridization. Because mulberry flowers are open for cross-pollination, the seeds thus col-
lected serve mainly as sources of stock material for grafting.
In general, a deficiency of hormone must be created experimentally (as by removing young leaves
or using a hormone-deficient mutant) to show that adding a hormone has an effect. In this respect, the
Mitscherlich law of diminishing return can be modified as follows: the increase in plant response pro-
duced by a unit increment of a deficient (limiting) hormone is proportional to the decrement of that hor-
mone from the maximum.
Mulberry varieties that do not ordinarily produce roots from a cutting are induced to root with ap-
plication of the requisite quantity of root hormones. The following chemicals are generally used, but their
efficiency varies from species to species and from variety to variety: (1) IAA, (2) IBA, and (3) NAA.
The objective of using growth regulators is to increase the percentage of cuttings that form roots, has-
ten root initiation, and increase the number of roots per cutting. IBA and NAA have proved to be better
in producing roots than other growth regulators.
The water requirement of mulberry does not differ greatly from species to species or from variety to
variety. The plant must be capable of absorbing water from soils of low moisture regimes. Generally re-
sistant plants should have well-developed root systems, hydrophilic colloids to absorb and hold water by
imbibition, and adaptations to facilitate the lowering of transpiration. In this regard, certain Japanese va-
rieties have a thick cuticle, sometimes a two-layered epidermis, a palisade parenchyma, and other bene-
ficial characteristics.
Although many tropical species root profusely through cuttings, certain temperate varieties do not
ordinarily produce roots. Root induction has been successfully achieved in the latter varieties by the (ar-
tificial) application of the requisite quantity of root hormones. However, the efficacy of the substances
varies from species to species and from variety to variety.
Development of the root primordium depends on the relative amount of natural auxin present in the
plant. Varieties that do not root apparently contain less auxin. The growth regulators act like auxins when
applied in small quantities and move upward in mass translocation through the xylem when the bases of
the cuttings are soaked in their solutions. The objective of treatment is to increase the percentage of cut-
tings that form roots, hasten root initiation, and increase the number of roots per cutting. Indole butyric
acid and naphthalene acetic acid appear to be better at producing roots than other agents [66,67]. The chem-
icals may be applied by various methods, including direct application of a powder, soaking the cuttings in
dilute solutions, dipping the cuttings in concentrated solutions, and application as a paste in lanolin.
136 SEN AND RAJPUT