Role of Entomophily and Artificial Pollination in Enhancing Quality and Yield of Seed Onion (Allium cepa L.) in Indian Himalayas

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Floral biology of onion composite variety “VL Piaz-3”

Floral Character	Details
Time of flower opening	From 6.20 h to 17.45 h (Throughout the day)
Anthesis	Early morning hours from 6.25 to 7.25 h
Anther dehisces	Observed from 7.45 h to 16.45 h
Stigma receptivity	High between 9.15 h to 15.15 h (Examined through Hydrogen peroxide method proposed by Zeisler (1933))
Number of flowers per umbel	Ranged between 682 to 1211 (842±132.51 average of 25 umbels)
Number of umbels per plant	Ranged between 4 to 13 (7.32±2.29 average of 25 plants)
Number of umbels per m2	Ranged between 19–65 (36.66±11.43 average of 12 plots)
Days for umbel formation	Ranged between 131–144 days (137.44±3.79 days* average of 100 plants) (19th February to 4th March, 2021)
Days for first flowering	Ranged between 143–155 days (149.96±6.54 days* average of 100 plants) (3rd march to 15th March, 2021)
Days for last flowering	Ranged between 203–216 days (209.92±3.96 days* average of 100 plants) (2nd May to 15th May, 2021)
Total flowering period of crop	Ranged between 60–73 days (67.76±3.83 days* average of 100 plants) (3rd March to 15th May, 2021)
Total flowering period of each umbel	Ranged between 13–19 days (15.92±1.98 days average of 25 umbels)

Foraging rate of pollen and nectar foragers of A_ c_ indica at three time intervals in a day during three flowering periods

	Pre peak flowering (<25%)					Peak flowering (>50%)					Post peak flowering (<25%)
Bee foragers	10.00 h	13.00 h	16.00 h	F-value	p-value	10.00 h	13.00 h	16.00 h	F-value	p-value	10.00 h	13.00 h	16.00 h	F-value	p-value
No. of flowers visited by pollen foragers	24.52±1.91 a	23.52±1.44 b	19.71±1.63 c	1.79*	0.018	31.86±2.72 a	29.86±1.79 a	30.57±2.92 a	0.41	0.863	27.48±6.49 b	28.95±5.53a	25.71±5.82 c	0.14	0.0098
No. of flowers visited by nectar foragers	23.42±2.13 b	26.41±1.57 a	23.54±1.95 b	0.64*	0.0069	16.33±1.98 b	17.69±2.01 b	19.11±1.38 a	1.65*	0.021	26.14±1.63 ab	27.18±1.25a	24.69±1.87 c	0.36*	0.0089
No. of umbels visited by pollen foragers	4.95±1.28a	4.19±0.94c	4.57±1.10b	3.68*	0.0261	3.24±0.74a	3.60±1.01a	3.45±1.03a	1.31*	0.32	4.14±0.79b	4.71±1.31a	4.19±1.03b	5.06*	0.0083
No. of visited by nectar foragers	3.98±1.01b	3.87±0.69c	4.23±0.98a	0.42*	0.0085	2.13±0.47c	3.01±0.57a	2.94±0.73b	0.67*	0.0099	4.23±1.03b	3.99±1.07c	4.57±0.87a	0.89	0.0053

Time spent in seconds by individual pollen and nectar forager bee of A_ c_ indica on onion flowers during three time frames and three flowering periods

	Pre peak flowering (<25%)					Peak flowering (>50%)					Post peak flowering (<25%)
Bee foragers	10.00 h	13.00 h	16.00 h	F-value	p-value	10.00 h	13.00 h	16.00 h	F-value	p-value	10.00 h	13.00 h	16.00 h	F-value	p-value
Pollen foragers	1.76±0.26 a	1.82±0.51 a	1.80±0.36a	1.91*	0.16	1.47±0.28a	1.34±0.31b	1.44±0.50a	0.80*	0.0058	1.79±0.4a 3	1.78±0.42a	1.77±0.45a	1.30*	0.32
Nectar foragers	3.04±0.61c	3.12±0.70b	3.30±0.62a	11.75*	0.0002	3.46±0.60b	3.28±0.62c	3.92±0.54a	2.57*	0.0077	2.96±0.63b	2.87±0.62c	3.08±0.62a	1.53*	0.0025

Pollen and nectar foragers of A_ c_ indica visiting onion flowers at three time intervals in 1 m2 area in a span of one minute during three flowering periods (averages from 3 flowering days)

	Pre peak flowering (<25%)					Peak flowering (>50%)					Post peak flowering (<25%)
Bee foragers	10.00 h	13.00 h	16.00 h	F-value	p-value	10.00 h	13.00 h	16.00 h	F-value	p-value	10.00 h	13.00 h	16.00 h	F-value	p-value
Number of pollen foragers	21.29±3.99 c	27.00±5.29b	30.71±5.99a	0.27*	0.0094	19.29±2.81c	39.00±7.90b	42.57±6.55a	1.72*	0.002	26.00±3.65c	43.43±4.79b	46.43±4.12a	1.96*	0.0014
Number of nectar foragers	78.71±3.99a	73.00±5.29b	67.86±3.34 c	0.69*	0.0006	80.71±2.81a	61.43±6.97b	57.43±6.55c	1.77*	0.0018	74.00±3.65a	56.57±4.79b	53.57±4.12c	0.87*	0.0048

Entomophily and artificial pollination methods followed for pollinating onion flowers

Treatments	Procedure of pollination	Treatments
T1- Indian bee (Apis cerana indica)	One individual bee, actively foraging in onion fields was collected through a test tube and released on to a pre-marked umbel and bagged with plastic mesh of 500 micron diameters to prevent escape. One bee per umbel was released every day from initiation of flowering up to seed set. Duration of release 1 hour
T2- European bee (Apis mellifera)
T3- Himalayan bumble bee (Bombus haemorrhoidalis)
T4- Hand gloves (Cloth)	The pollens were collected from un-bagged umbel through the cloth hand gloves and gently rubbed over the bagged umbel and covered with plastic mesh after pollination. Umbels were gently rubbed for 3 minutes
T5- Hand gloves (Rubber)	The pollens were collected from un-bagged umbel through the rubber hand gloves and gently rubbed over the bagged umbel and covered with plastic mesh after pollination. Umbels were gently rubbed for 3 minutes
T6- Sponge puff	The pollens were collected from un-bagged umbel through the puff and gently rubbed over the bagged umbel and covered with plastic mesh after pollination. Umbels were gently rubbed for 3 minutes
T7- Camel Brush	The pollens were collected from un-bagged umbel through the camel brush and gently sprinkled over the bagged umbel and covered with plastic mesh after pollination. Pollens were sprinkled for 3 minutes
T8- Control (Open)	The umbels were not covered and allowed for free cross pollination by all the pollinating agents
T9- Control (Close)	The umbels were covered with plastic mesh and only self-pollination was allowed

Quantitative seed yield data of onion obtained through entomophily and artificial pollination methods

Treatments	Fruit set (in %)	Average number of seeds per umbel	Seed weight per Umbel (in grams)	Test weight of seeds (in grams)	Yield per ha (in kg)
A. c. indica	46.79	394±6.35b	1.38±0.18b	4.2±0.01b	503.70
A. mellifera	36.46	307±9.02c	1.05±0.22c	3.9±0.02c	383.25
B. haemorrhodalis	21.26	179±4.36d	0.82±0.11d	2.8±0.02d	299.30
Hand gloves (cloth)	11.40	96±3.00f	0.38±0.11g	3.3±0.02e	138.70
Hand gloves (rubber)	8.79	74±3.61g	0.34±0.09h	2.9±0.03g	124.10
Sponge puff	17.34	146±4.73e	0.66±0.19e	3.1±0.02f	240.90
Camel brush	17.10	144±4.58e	0.59±0.15f	2.6±0.01h	215.35
Control (open)	85.99	724±7.00a	3.90±0.47a	4.7±0.01a	1423.50
Control (close)	7.84	66±4.04h	0.31±0.04i	2.2±0.01i	113.15
SE(m)		12.98	0.215	0.013
C.V.		3.141	64.95	6.913
F-values		2461.78*	27.41*	38.67*
p-values		0.00014	0.00007	0.000011

List of insects visiting onion flowers under Himalayan conditions of Uttarakhand, India

Order of insect flower visitors	List of insects visiting onion flowers
Hymenoptera (19 species)	Apis cerana indica, Apis mellifera, Apis dorsata, Apis florea, Bombus haemorrhoidalis, Vespa tropica, Vespula vulgaris, Andrena hilaris, Megachile rotundata, Osmia inermis, Nomia incerta., Halictus sexcinctus, Ceratina smaragdula, Trigona iridipennis, Xylocopa latipes, Sceliphron curvatum, Megascolia azurea, Ceratina sutepensis, Lithurgus atratus
Lepidoptera (17 species)	Celastrina argiolus, Chilades pandava, Danaus chrysippus, Pieris brassicae, Parantica aglea, Euploea core, Aglais caschmirensis, Vanessa cardui, Junonia lemonias, Papillio demoleus, Colias ladakensis, Helicoverpa armigera, Lymantria dispar, Acherontia styx, Pieris rapae, Chilades parrhasius, Danaus genetua
Diptera (14 species)	Episyrphus balteatus, Metasyrphus corollae, Eupeodes luniger, Eristalis tenax, Macronomia spp., Calliphora vomitoria, Lucilia cuprina, Musca domestica, Eristalinus quinquelineatus, Sarcophaga carnaria, Helophilus trivittatus, Liosarcophaga dux, Eristalis horticola, Eristalinus megacephalus
Coleoptera (5 species)	Oxycetonia versicolor, Clinteria kluge, Chiloba acuta, Heterorrhina elegans, Rhomborrhina spp.