EFFECT OF POLLEN GRAIN SOURCES ON FRUIT SET AND RETENTION IN 'SHAHI' LITCHI

Abstract

The effect of self-and cross-pollination on fruit set and fruit retention in 'Shahi' litchi was investigated. The enclosed flower panicles were hand pollinated with male (M 2) pollen from 'Rose Scented', 'Swarna Roopa', 'Bedana', 'China' and 'Shahi' flowers. The current season's pollen and one year old pollen stored at 4 °C were used for pollination. The number of fruit set and fruit retention per panicle was determined throughout the fruit development period from fruit set to harvest on a weekly basis. Initial fruit set in 'Shahi' was lower with sources 'Swarna Roopa' and 'Bedana' compared to the self-pollination with 'Shahi'. However, final fruit retention in 'Shahi' was higher with all sources used for cross-pollination whereas there was no fruit retention in self pollination. Results indicated that cross-pollination in 'Shahi' litchi is essential for fruit set and fruit retention. The limited number of initial fruit set resulted in high retention of fruits (19.29 % and 15.30%) in 'Shahi' with current season and one year old pollen of 'Swarna Roopa'.

Full text

VOL. IX, ISSUE XXIX, APRIL 2019 MULTILOGIC IN SCIENCE ISSN 2277-7601
An International Refereed, Peer Reviewed & Indexed Quarterly Journal in Science, Agriculture & Engineering
www.ycjournal.net NAAS Rating- 5.20 Impact factor-4.035 152
EFFECT OF POLLEN GRAIN SOURCES ON FRUIT SET AND RETENTION IN ‘SHAHI’ LITCHI
*Narayan Lal1, AK Gupta2, ES Marboh3, Abhay Kumar4 and Vishal Nath5
ICAR- NRC on Litchi, Muzaffarpur-842002, Bihar
1,2,3,4 Scientist, ICAR-NRC on Litchi, Muzaffarpur, Bihar
5Director, ICAR-NRC on Litchi, Muzaffarpur, Bihar
(Received: 05.03.2019; Revised: 22.03.2019; Accepted: 23.03.2019)
(RESEARCH PAPER IN HORTICULTURE)
Abstract
The effect of self- and cross-pollination on fruit set and fruit retention in ‘Shahi’ litchi was investigated. The enclosed flower panicles were
hand pollinated with male (M2) pollen from ‘Rose Scented’, ‘Swarna Roopa’, ‘Bedana’, ‘China’ and ‘Shahi’ flowers. The current season’s
pollen and one year old pollen stored at 4 °C were used for pollination. The number of fruit set and fruit retention per panicle was
determined throughout the fruit development period from fruit set to harvest on a weekly basis. Initial fruit set in ‘Shahi’ was lower with
sources ‘Swarna Roopa’ and ‘Bedana’ compared to the self-pollination with ‘Shahi’. However, final fruit retention in ‘Shahi’ was higher
with all sources used for cross-pollination whereas there was no fruit retention in self pollination. Results indicated that cross-pollination
in ‘Shahi’ litchi is essential for fruit set and fruit retention. The limited number of initial fruit set resulted in high retention of fruits (19.29
% and 15.30%) in ‘Shahi’ with current season and one year old pollen of ‘Swarna Roopa’.
Key Words: Self and cross pollination, fruit set, fruit retention, current season pollen, one year old pollen
Introduction
Litchi (Litchi chinensis Sonn.) is an important commercial fruit crop
grown extensively in Bihar, West Bengal, Assam, Jharkhand,
Uttarakhand and Odisha states of India. The panicle initiation start
during last week of January to first week of February and become
fully developed during March in Bihar condition. However, the
panicle development depends on prevailing weather condition and it
varies from first week of March to last week of March. Litchi flowers
are borne on multi-branched terminal inflorescences, which are
generally referred as panicles. A panicle can have up to 3,000 flowers
(Lal, 2018), although only about 200 are pollinated and of these only
5 to 60 will develop into mature fruit. There are three distinct flower
types, two male types (M1 and M2 flower) and one female (F flower),
which are all borne on the same panicle. Sometimes, M1 flower is
omitted to produce by some cultivars of litchi mostly during young
stage of plants and only two flowers M2 and F flower are produced.
The usual sequence of flower opening, which occurs over a 2 to 6
week period, is male flower (M1), female hermaphrodite flowers
which set fruits and male hermaphrodite flowers (M2) that do not set
fruit. The male flowers in the first and third stages release pollen to
fertilize the female flowers. Most of the pollen used for fertilization
is usually supplied by the third stage of male hermaphrodite flowers
(M2) and staining results revealed that M2 pollen were more viable
than M1 (Gupta et al., 2018). Thus, there needs to be an overlap of
the male stages with the female stage to promote self-pollination.
The success of fruit set depends upon male parents irrespective of
cultural and environmental condition. ‘Shahi’, a early and high
yielding commercial litchi cultivar grown in major parts of India.
However, the cultivar is harvested at a time in India when there is a
gap in worldwide litchi production, thereby increasing its
profitability. The fruit drop in one of the major detrimental factor
which lowers the production (Lal et al., 2017). Therefore, retention
of fruit is very important for high production in any crops. An
obvious field of study would therefore be to investigate ways of
improving fruit set and retention to enhance the appeal of ‘Shahi’ on
local and overseas markets. One of the factors found to be involved
in fruit set and retention in litchi is pollen source. The pollen parent
can have an effect on yield of litchi fruit (Stern et al., 1993; Degani
et al., 1995). The importance of pollen sources are experienced in
avocado (Gazit and Gafni, 1986; Degani et al., 1989). Stern and
Gazit (2003) showed that the litchi flowering pattern tends to
promote cross-pollination. However, the partial overlap between the
female flowering and male flowers enables pollination among
flowers on the same tree, or among trees of the same cultivar, thereby
providing an opportunity for self-pollination (Stern and Gazit, 1996;
Lal, 2018). Litchi is considered to be self-fertile, since single cultivar
litchi orchards are capable of producing good yields. Many
researchers from South Africa (Fivaz and Robbertse, 1995), Israel
(Stern and Gazit, 1998), and Australia (Batten and McConchie,
1992) confirmed the self-compatibility of several litchi cultivars.
However, some pollen parents increased fruit set in certain cultivars
(Stern and Gazit, 2003). The opening of female flower overlaps with
the male flowers which increases chances of self-pollination (Lal,
2018) but cross pollination is very important in litchi for higher
production. Fruit set and its retentions are very important for higher
productivity and fruit retention depend upon the male parents who
provide pollen grain for pollination and fertilization. Rai and
Srivastav (2012) clearly shown the importance of cross pollination
in litchi for enhancing production Therefore, present study was
undertaken to assess the effect of pollen sources on fruit set and fruit
retention in ‘Shahi’ litchi.
Materials and Methods
An experiment was conducted during 2017 and 2018 in Field Gene
Bank at ICAR-NRC on Litchi, Muzaffarpur to assess the effect of
pollen sources on fruit set and fruit retention in ‘Shahi’ litchi. The
trial was laid out as a randomised complete block design (RCBD).
Five panicles for each pollen source were marked on ‘Shahi’ that was
used as the female parent. Litchi produces three types of flower male
(M1), female (F), hermaphrodite male (M2) flower and M2 flower is
more fertile than M1 flower. When all M1 flowers were dropped off,
panicles were bagged before a day of opening of female flowers and
next day bag was opened and removed all M2 flowers. Pollen of
different male source parents ‘Rose Scented, ‘Swarna Roopa’, ‘
Bedana’ ‘China’ and ‘Shahi’ were applied to the stigma of female
flowers (Shahi) after which the panicles were again enclosed with
perforated nylon bag to prevent unwanted cross-pollination by
insects or wind. Pollens were primarily obtained from M2 flowers of
the pollen source cultivars, coinciding with the late female bloom of
‘Shahi’. Pollination was performed at anthesis when the surface of
the stigma of female flowers was shiny white. Replications
comprised of three trees. The aim of study was to determine the
effect of self and cross-pollination on fruit set and fruit retention in
‘Shahi’ litchi. Data from ‘Shahi’ panicles was taken by counting the
number of fruit set per replication after the pollination process on a
weekly basis. The fruit set was monitored by counting the number of
fruit retained per panicle on a weekly basis until harvest to determine
fruit retention. Data were statistically analysed as a completely
randomised design with 5 treatments and 3 replications. Analysis of
variance (ANOVA) was used to test for differences between the five
pollen treatment effects. The data were acceptably normal with
homogeneous treatment variances. Treatment means were separated
using Fisher’s protected t-test least significant difference (LSD) at
the 5% level of significance (Snedecor and Cochran, 1980)
Results and Discussion

VOL. IX, ISSUE XXIX, APRIL 2019 MULTILOGIC IN SCIENCE ISSN 2277-7601
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The initial fruit set and final fruit retention are presented in Figure 1
& 2 and a trend of pollen source effect on fruit set and subsequent
fruit retention of ‘Shahi’ on 15 flower panicles per treatment is
demonstrated in Figure 3 & 4. Initial fruit set in ‘Shahi’ panicles were
higher in all cross-pollinating treatments compared to self-
pollination with ‘Shahi’ except ‘Swarna Roopa’ and ‘Bedana’.
However, final fruit retention was higher in all the cross-pollinating
treatments as opposed to self-pollination with ‘Shahi’. Compared to
self-pollination with ‘Shahi’ pollen, a significantly lower (P<0.05)
initial fruit set (10.42, 20.71 and 4.38, 19.46 %) was found with
pollen sources ‘Swarna Roopa’ and ‘Bedana’ respectively (Fig. 2) in
both current season’s pollen and one year old pollen. Kumari et al.
(2018) found higher fruit set in cross pollination as compare to self-
pollination. In contrary to this result Brijwal et al. (2016) had
reported that initial fruit set under self-pollination was significantly
higher than all crosses and open-pollination methods. Forneman et
al. (2012) also reported the lower initial fruit set in all cross-
pollination as compared to self-pollination in “Wai Chee” litchi
cultivar.
The maximum fruit retention in Shahi (19.29% and 15.30 %) was
found with source ‘Swarna Roopa’ of current season’s pollen and
one year old pollen. Although, the initial fruit set was least in Shahi
with source ‘Swarna Roopa’. The lower numbers of initial fruit set
efficiently used food materials which resulted in high retention of
fruits. Others sources resulted with higher initial fruit set where more
competition occurs among more numbers of fruitlets resulting more
fruit drop and low retention of fruit at harvest. However, there was
no fruit retention at harvest in self-pollination with source ‘Shahi’
and cross pollination with other sources enhanced fruit set and fruit
retention. Kumar and Kumar (2014) and Srivastava et al. (2017) also
reported that cross pollination enhanced fruit set than bagged
panicle/self-pollination. Degani et al. (1995) reported that in-bred
fruit often abscise early, supporting the findings of this study. The
better fruitlet retention with cross-pollination may also be explained
by embryo degeneration and abortion found in self-pollinated fruit
due to inbreeding depression (Sedgley and Griffin, 1989). A great
number of fruit drop prematurely reduces the crop potential. This
fruit drop pattern was also clear in ‘Shahi’ after hand pollination of
female flowers. The significant effect of pollen source on litchi fruit
set and retention in ‘Shahi’ became evident as the number of fruits
that survived throughout the development period was monitored.
Results in this study showed that self-pollinating ‘Shahi’ gave the
highest initial fruit set compare to source Swarna Roopa’ and
‘Bedana’, but fruitlets emanating from these self-pollinations
abscised at a higher rate than the fruitlets resulting from cross-
pollination and there was no fruit retention in self pollination at
harvest. The significant increases in fruit retention obtained with all
sources pollen may be an indication of potential enhancing effects of
cross pollinators on yield in ‘Shahi’. The actual fruit set is
considered in litchi two weeks after pollination and during second
week, compared to self-pollination with ‘Shahi’ pollen, a
significantly lower (P<0.05) initial fruit set (2.31%) was found with
pollen sources ‘Bedana’ when current season’s pollens were used
(Fig 3). However, ‘Shahi’ as pollen source retained significantly less
fruit set than current sesason pollen sources ‘Rose Scented’, ‘Swarna
Roopa’, and ‘China’ while all sources retained more fruit set with
one year old pollens (Fig 4).
In order to determine the significance of pollen source between 2 and
8 weeks, the percentage fruit retained on each week relative to initial
fruit set was analysed. Compared to self-pollination with ‘Shahi’
pollen, a significantly lower (P<0.05) final fruit retention (9.39%)
was found with pollen sources ‘Rose Scented’ when current season’s
pollens were used (Fig 5). However, ‘Shahi’ as pollen source
retained significantly less fruit retention than cross-pollinating
treatments ‘Swarna Roopa, China and Bedana’ with current season’
pollens while all sources retained more fruit retention with one year
old pollens (Fig 6). Fruit retention deceased with the passes of time
till 7 weeks and afterwards become constant. When the percentage
fruit retained relative to initial fruit set was analysed, it was found
that pollen source had a statistically significant effect on fruit
retention during certain stages of fruit development. Retention of
fruit started decrease after first week, but after a pronounced fruit
drop period of three weeks, cross-pollinating sources had a
significantly higher influence on fruit retention during the later
stages of fruit development. Degani et al. (1995) reported that in-
bred fruit often abscise early, supporting the findings of this study.
The better fruitlet retention with cross pollination may also be
explained by embryo degeneration and abortion found in self
pollinated fruit due to inbreeding depression (Sedgley and Griffin,
1989). Final fruit retention at harvest was higher in all cross-
pollinating sources, demonstrating the potential ability of cross-
pollinated fruitlets to outcompete self-pollinated fruitlets for
available tree resources.
Conclusion
Results obtained in this study have shown a positive response of
‘Shahi’ towards different pollen source applications aiming to
enhance fruit set and fruit retention in the cultivar. The limited
numbers of initial fruit set resulted in final high retention of fruits.
Final fruit retention with cross-pollinating sources was all higher
than with self-pollination. Results therefore indicate that the
inclusion of pollen sources to encourage cross-pollination in litchi
orchards may have beneficial effects on production. Work in this
study was mainly focused on the ‘Shahi’ cultivar. However, it would
be worthwhile to include some other litchi cultivars in future
investigations to determine the effect of cross-pollination on these
cultivars. Due to environmental effects it could also be worthwhile
to repeat this trial over consecutive seasons to determine the
economic impact of the pollen source on various fruit characteristics
over a period of time.
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Fig 1: Pollen source (Current season) effect on the initial fruit set and final fruit retention of the cultivar ‘Shahi’. Data are means
of 15 panicles per treatment (5 panicles x 3 trees) of male parents ‘Rose Scented’, ‘Swarna Roopa’, ‘Bedana’, ‘China’ and ‘Shahi’.
Fig 2: Pollen source (One year old) effect on the initial fruit set and final fruit retention of the cultivar ‘Shahi’. Data are means of
15 panicles per treatment (5 panicles x 3 trees) of male parents ‘Rose Scented’, ‘Swarna Roopa’, ‘Bedana’, ‘China’ and ‘Shahi’.

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Fig 3: Trend of pollen source (Current season) effect on per cent of fruit set weekly on ‘Shahi’ panicles from fruit set (2 week) to
harvest (8 week). Data are means of 15 panicles per treatment (5 panicles x 3 trees) of male parents ‘Rose Scented’, ‘Swarna
Roopa’, ‘Bedana’, ‘China’ and ‘Shahi’.
Fig 4: Trend of pollen source (One year old) effect on per cent of fruit set weekly on ‘Shahi’ panicles from fruit set (2 week) to
harvest (8 week). Data are means of 15 panicles per treatment (5 panicles x 3 trees) of male parents Rose Scented’, ‘Swarna Roopa’,
‘Bedana’, ‘China’ and ‘Shahi’.

VOL. IX, ISSUE XXIX, APRIL 2019 MULTILOGIC IN SCIENCE ISSN 2277-7601
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Fig 5: Effect of pollen source (Current season) on percentage fruit retained in ‘Shahi’ relative to the initial fruit set. Percentages
were calculated as the number of fruit retained relative to the initial fruit set on week 1. This was done on a weekly basis until
harvest (week 8). Data are means of 15 panicles per treatment (5 panicles x 3 trees) of male parents Rose Scented’, ‘Swarna Roopa’,
‘Bedana’, ‘China’ and ‘Shahi’.
Fig 6: Effect of pollen source (One year old) on percentage fruit retained in ‘Shahi’ relative to the initial fruit set. Percentages
were calculated as the number of fruit retained relative to the initial fruit set on week 1. This was done on a weekly basis until
harvest (week 8). Data are means of 15 panicles per treatment (5 panicles x 3 trees) of male parents Rose Scented’, ‘Swarna Roopa’,
‘Bedana’, ‘China’ and ‘Shahi’.