Guava (Psidium guajava L.)
is an important fruit crop of India. It has gained considerable prominence on
account of its high nutritive value, availability at moderate prices, pleasant
aroma and good flavour. It is one of the commonest fruits liked by the rich and
the poor alike and is popularly known as ‘apple of the tropics’. It is one of
the hardiest fruit trees, adaptable to a variety of soil and climatic
conditions. It is the fifth most widely
grown fruit crop of India. The area under guava is about 0.246 million
hectares, producing 3.99 MT of fruit (NHB-2015). Popular varieties of guava in
India are Allahabad Safeda, Lucknow-49,Lalit etc. Uttar Pradesh is the leading state in guava area and
production, followed by Bihar,
Maharashtra, Karnataka, West Bengal, Punjab, Andhra Pradesh, Gujarat, Orissa
and Tamil Nadu. At present, it is grown through out the country right from sea
level to1300m altitude, and is so acclimatized that it seems like a native of
India. Guava is a rich source of vitamin C and pectin. Guava fruit contains
82.5% water, 2.45% acids, 4.45% reducing sugars, 5.23% non-reducing sugars, has
9.73 % TSS, 0.48% ash and 260 mg vitamin C/100g fruit (which differ with
cultivar, stage of maturity and season
F
The knowledge of flower bud
development, time of anther dehiscence and anthesis, extent of fruit set and
degree of cross pollination are a pre-requisite for planned hybridization for
crop improvement. In guava, flower buds are borne in leaf axil on current
season’s growth, either singly or in cymose of two or three (Braganza, 1990).
Guava is reported to require about 30 days in Northern India from flower bud
differentiation to complete development upto the calyx cracking stage (Singh
and Sehgal, 1968). However, under Southern conditions, Braganza (1990) reported
that the period varied from 45 to 51 days. The flowers consist of a superior
calyx with five lobes and the corolla consists of 6 to 10 petals arranged in
one or two whorls. The androecium consists of 160 to 400 thin filaments
carrying bilobed anthers, closely packed together. The gynoecium consists of an
inferior ovary, syncarpous, with axillary placentation and subulate style. The
style is smooth and bearded at the summit. Three flowering seasons, viz., ‘Ambe
bahar’, ‘Mrig bahar’ and ‘Hatti or Hasta bahar’ have been reported in the
peninsular regions of India (Cheema et al 1954). However, some workers reported
only two flowering seasons (Sehgal and Singh, 1967; Sachan et al, 1969;
Srivastava, 1974; Syamal et al, 1980; Ojha et al, 1986). In guava, it has been
observed that the flowering season does vary between regions. Generally, three
flowering seasons are recognized in the tropical South India and only two
seasons in the subtropical North India. In guava, peak anthesis was found to be
between 6 and 7.30 A.M. under North Indian conditions (Singh and Sehgal, 1968).
Dehiscence of anthers was observed to take place 15 to 30 minutes after
anthesis and continued upto 2hrs (Balasubramanyam, 1959). Pollen fertility has
been generally found to be high in guava (78 to 91%) in diploid varieties. The
pollen is reported as round with large grains (Srivastava, 1974). Stigmatic
receptivity, as studied by fruit set following controlled pollination, was
observed to be
maximum on the same day as anthesis.
Stigma was found to be receptive two days before dehiscence, extending upto 4
days (Singh and Sehgal, 1968). Guava is largely a self-pollinated crop, but
cross- pollination also does occur. This results in a large variability in the
seedling population from which promising genotypes have been selected in
different agro-climatic regions of the country.
Hybridization technique
Ø Single
central bold bud or flower is chosen for hybridization programme and rest small
flower are removed.
Ø Flowers
that are chosen for crossing are emasculated when at the ‘calyx break stage’, a
day before opening (fig b ).
Ø Pollen
from the pollen parent is brought from an unopened flower, at preferrably at
calyx break stage.
Ø The
stigmatic surface of emasculated is gently smeared with the pollen and flowers
are bagged.
Ø Under
Southern condition pollination carried out during the morning hours between 10
AM to 11.45 AM has given better results.
Ø Under
North Indian Conditions during the month of April pollinations are carried out
during 9-10.30 AM and during month of May 8-10 AM were found better and has
given good fruit set.
Ø Once
pollination of desired pollen is over care should be taken to cover the flowers
with butter paper cover with proper ventilation
Ø Proper
labelling is done with details of the crosses (female and male parent) and date of crossing.
Ø Third
day of pollination the covers can be removed
Ø Proper
care including irrigation to be done in order to have proper fruit set
Ø Areas
with fruit fly infestation the fruits can be bagged in order to avoid damage by
fruit fly
Ø At
full maturity or riped fruits are harvested and the seeds are extracted and
sown fresh in proper potting media
The F1
hybrids are transplanted in the filed when the seedling attains a minimum of
six months old 