The study was conducted in the Agriculture Research Station, Bhavanisagar, Tamil Nadu, using the following treatments.
T1: 5’x 5’ spacing plot
T2: 6’x 6’ spacing plot
T3: 7’x 7’ spacing plot
Double-hybrid silkworms were purchased from private Chawki Rearing Centres after the second moult. Disinfection of the rearing room was done, using bleaching powder and Sanitech solution.
Bioassay on silkworm
The study was conducted using the 3rd to 5th instar worms and allowed to feed on healthy leaves of different spaced tree types of mulberry leaves. The silkworms were reared at an optimum temperature and RH. For every treatment, three replications were kept, and each replication had fifty silkworms. The following parameters were recorded during the experiment described below
i)Larval weight (in Grams)
ii)Effective rate of rearing (ERR) %.
No. of cocoons harvested
ERR = -------------------------------------------------------- × 100
Total number of worms brushed.
iii)Mortality rate (%)
Number of worms died
Mortality = ----------------------------------------------- × 100 (Dayananda et al. 2011)
Total unit of worms brushed
iv)Silk gland weight (in Grams)
v)Silk productivity
Silk filament weight (cg)
Silk productivity (cg/day) = -------------------------------------------------------------------------- (Aruna et al., 2018)
Total larval duration @ fifth instar (days)
vi) Single Cocoon weight (in Grams)
vii) Pupal weight (in Grams)
viii) Shell weight (in Grams)
ix) Shell ratio (%)
Shell weight (g)
Shell ratio = ------------------------------------------------------- X100
Cocoon weight (g)
x)Cocoon yield (by weight)
Weight of good cocoons
Cocoon yield /10000 larvae = ----------------------------------------------------------------- X 10000
Number of healthy worms retained in the fifth instar
xi)Total Silk filament length
L = R x 1.125
Where L = Total length of the filament
R = Number of revolutions made
1.125 = Circumference of the reeler machine in meters.
xii)Silk filament weight (in Grams)
Silk filament obtained during reeling activity was weighed individually and expressed in grams.
xiii)Denier (thickness of the silk filament)
Weight of the filament in grams
Denier = ---------------------------------------------------------------------------- X 9000
Length of the filament in meters
xiv) Renditta
10000
Renditta (kgs) = ----------------------------------------------------------------------------
Shell ratio in percentage x Raw silk recovery @70 %
Statistical analysis
The data obtained from the experiments were critically analyzed using the Completely Randomized Design (CRD) method, as outlined by Fisher. The AGRES software package (version 0.74) was employed to analyze the stage-wise data.
Results and Discussion
Effect of different spacing of tree-type mulberry leaves on silkworm larval parameters
The mature larval weight was observed to be high when silkworms were reared on the 6 ft x 6 ft leaves (3.30 g), followed by 7 ft x 7 ft (3.08 g) leaves. Among the different varieties, mature larval weight was recorded to be higher for V1 (3.13 g) and comparable to G4 (3.03 g). Notable variations are evident to the interaction of spacing and varieties when fed to the silkworm (Table 1). The present results align with Marin et al. (2022), who recorded larval weight of 3.59 g by feeding V1 leaves. Tree-type mulberry leaves significantly influenced ERR with a maximum of 92.51 per cent in 6 ft x 6 ft, closely followed by 7 ft x 7 ft (90.57 %), which were statistically on par with each other. Regarding varieties, ERR was significantly higher in V1 (93.56%) and was found to be comparable to the G4 (91.47%) variety. This agrees with Jini et al. (2022), who registered an ERR of 87.0 percent when offering V1 leaves to the silkworm. In interaction studies, there was a statistically significant difference with ERR in the spacing and varieties (Table 1). The silkworm mortality rate showed significant variation with respect to the different spacings of V1 and G4 leaves. Lowest mortality was evidenced in 6 ft x 6 ft (7.25 %), followed by 7 ft x 7 ft (8.70 %), and higher mortality occurred in 5 ft x 5 ft (10.06 %) (Table 1). Susikaran and Vijay (2024) reported that significant improvement in larval parameters was observed when fed with mini clonal mulberry leaves to silkworm, treatment 60 DAP-AC (V1) recorded an increase in larval weight (3.15 ng), higher ERR (86.34 %), and lower larval mortality (13.46 %) than the check.
Table 1. Effect of different spacing of tree-type mulberry leaves on silkworm larval parameters
|
Treatments
|
Larval weight (g)
|
ERR (%)
|
Mortality (%)
|
|
V1
|
G4
|
Mean
|
V1
|
G4
|
Mean
|
V1
|
G4
|
Mean
|
|
5ft x 5ft
|
2.92
|
2.86
|
2.89
|
89.08
|
87.98
|
88.53
|
8.56
|
11.56
|
10.06
|
|
6ft x 6ft
|
3.36
|
3.24
|
3.30
|
93.56
|
91.47
|
92.51
|
6.08
|
8.43
|
7.25
|
|
7ft x 7ft
|
3.12
|
3.01
|
3.06
|
91.43
|
89.71
|
90.57
|
7.74
|
9.67
|
8.70
|
|
Mean
|
3.13
|
3.03
|
3.08
|
91.35
|
89.72
|
90.53
|
7.46
|
9.88
|
8.67
|
|
CD (P=0.05)
|
T
|
0.17**
|
4.34**
|
0.56**
|
|
V
|
0.14**
|
3.64**
|
0.46**
|
|
T X V
|
0.32**
|
NS
|
NS
|
*Significant, ** Highly Significant, NS – Non-Significant; Each value is the mean of six replications and the pooled mean of two crops
Different spacing of tree-type mulberry has a significant impact on silk gland weight (Fig.1). It was registered highest in 6 ft x 6 ft (788.56 mg), which was statistically superior compared to all other treatments, and this was followed by 7 ft x 7 ft (777.71 mg). Among the different varieties, the silk gland weight was recorded to be highest for V1 (789.99 mg), followed by G4 (766.00 mg). Statistically, no significant difference was observed in the interaction studies concerning silk gland weight. In silkworm rearing, maximum silk productivity was recorded on treatment 6 ft x 6 ft (6.70 cg/day) and next best performed by 7 ft x 7 ft (6.22 cg/day) (Fig. 1). The highest productivity was evidenced in V1 (6.59 cg/day), followed by G4 (6.07 cg/day). In an interaction between different spacings and varieties, significantly higher silk productivity (6.07 cm/day) was recorded in the V1 variety at 6 ft x 6 ft, statistically superior to all other treatments. At the same time, a minimum silk productivity of 5.82 cg/day was observed in G4 at 5 ft x 5 ft. Similarly, Murugesh et al. (2022) recorded silk productivity of 4 cg/day by offering V1 foliage to the silkworm.
Effect of different spacing of tree-type mulberry leaves on cocoon parameters.
Cocoon weight did vary statistically between spacing when the leaves were fed to the silkworm (Table 2). A higher cocoon weight of 1.80 g was observed in the 6 ft x 6 ft area, followed by 1.64 g. On comparing varieties, V1 had a statistically high value of cocoon weight (1.99 g), followed by G4 (1.87 g), mulberry leaves fed to the silkworm. Statistically, no significant difference was observed in the interaction studies concerning cocoon yield. These results are by the findings of Some et al., (2019) who observed a cocoon weight of 1.87 g when fed with V1 mulberry leaves. Shell weight significantly varied between different spaced tree type mulberries, with higher values recorded in 6 ft x 6 ft (0.38 g). The subsequent best treatment was 7 ft x 7 ft (0.37 g). Regarding varieties, notably high in V1 (0.38 g) and the next best was G4 (0.35 g). The interaction between spacing and variety indicates that a significantly higher shell weight was found in V1 (0.40 g) with 6 ft x 6 ft, and the lowest shell weight was recorded in 5 ft x 5 ft (0.32 g). Tulu et al. (2016) also reported similar results, recording a shell weight of 0.37 g when provided with V1 mulberry leaves. Singh et al. (2021) further supported it, who registered 0.29 g shell weight by offering V1 leaves. Significantly higher shell ratio was obtained when silkworms were reared on 6 ft x 6 ft spaced leaves (23.00 %), followed by 7 ft x 7 ft (22.49 %) leaves. of varieties, both V1 and G4 had maximum shell ratios of 22.37 and 22.07 per cent, respectively, which were statistically on par with each other. Significantly more shell ratio was found in V1 of 6 ft x 6 ft (23.12%) in interaction of spacing and varieties followed by G4 of 6 ft x 6 ft (22.89%) and lowest shell ratio of 21.01 per cent was noted in the 5 ft x 5 ft of G4 (Table 2). The present results are also with the findings of shell ratio of 20.26 percent when feeding V1 leaves.
Table 2. Effect of different spacing of tree-type mulberry leaves on cocoon parameters
|
Treatments
|
Cocoon weight (g)
|
Shell weight (g)
|
Shell ratio (%)
|
|
V1
|
G4
|
Mean
|
V1
|
G4
|
Mean
|
V1
|
G4
|
Mean
|
|
5ft x 5ft
|
1.54
|
1.51
|
1.52
|
0.36
|
0.32
|
0.34
|
21.34
|
21.01
|
21.17
|
|
6ft x 6ft
|
1.82
|
1.78
|
1.80
|
0.40
|
0.37
|
0.38
|
23.12
|
22.89
|
23.00
|
|
7ft x 7ft
|
1.68
|
1.60
|
1.64
|
0.38
|
0.36
|
0.37
|
22.67
|
22.32
|
22.49
|
|
Mean
|
1.68
|
1.63
|
1.65
|
0.38
|
0.35
|
0.38
|
22.37
|
22.07
|
22.67
|
|
CD (P=0.05)
|
T
|
0.11**
|
0.02**
|
1.46**
|
|
V
|
0.08**
|
0.01**
|
1.18**
|
|
T X V
|
NS
|
0.04*
|
3.54*
|
*Significant, ** Highly Significant, NS – Non-Significant; Each value is the mean of six replications and the pooled mean of two crops
Different spacing treatments have significantly influenced cocoon yield (Table 3). A higher cocoon yield was found in 6 ft x 6 ft (20.56 kg), which performed statistically well compared to all other treatments, followed by 7 ft x 7 ft (19.49 kg). In respect to varieties, it was notably high in V1 (20.30 kg) and followed by G4 (18.81 kg) variety. Interaction studies show that V1 registered the highest cocoon yield in 6 ft x 6 ft planted with 21.56 kg, and the lowest yield was noticed in 5 ft x 5 ft (18.21 kg) planted G4 leaves. Similar findings were recorded by Dayananda et al. (2011) in the double-hybrid silkworm. Pupal weight readings were statistically analyzed and showed significant variation due to the different spacing of tree type mulberry (Table 3). It ranged from 1.22 g, 1.33 g, and 1.25 g, respectively, with their spacing. By feeding V1 leaf foliage, maximum pupal weight was observed in 6 ft x 6 ft (1.29 g) and found statistically superior, followed by 6 ft x 6 ft (1.24 g) of G4. In the interaction studies, V1 planted 6 ft x 6 ft spaced leaves fed to silkworm with a pupal weight of 1.36 g, and the lowest was recorded in 5 ft x 5 ft of G4 (1.20 g). The results align with Balasundaram et al. (2013) who reported pupal weights of 1.03 g and 1.57 g by feeding MR2 and V1 leaves to the double hybrid silkworm.
Table 3. Effect of different spacing of tree-type mulberry leaves on cocoon parameters
|
Treatments
|
Cocoon yield/10,000 larvae
|
Pupal weight
|
|
V1
|
G4
|
Mean
|
V1
|
G4
|
Mean
|
|
5ft x 5ft
|
19.02
|
18.21
|
18.61
|
1.24
|
1.20
|
1.22
|
|
6ft x 6ft
|
21.56
|
19.56
|
20.56
|
1.36
|
1.31
|
1.33
|
|
7ft x 7ft
|
20.30
|
18.67
|
19.49
|
1.28
|
1.23
|
1.25
|
|
Mean
|
20.30
|
18.81
|
19.55
|
1.29
|
1.24
|
1.26
|
|
CD (P=0.05)
|
T
|
1.23**
|
0.07**
|
|
V
|
1.01**
|
0.05**
|
|
T X V
|
2.85**
|
1.01**
|
*Significant, ** Highly Significant, NS – Non-Significant; Each value is the mean of six replications and the pooled mean of two crops
Effect of different spacing of tree-type mulberry leaves on reeling parameters.
Silkworm fed with tree-type mulberry leaves showed significant variation concerning filament length of cocoon (Fig.2 ). Significantly higher filament length of 1318.99 and 1283.34 m was recorded in 6 ft x 6 ft and 7 ft x 7 ft leaves, respectively, and were on par with each other. Regarding varieties, the longest filament length was reeled in V1 (1286.00 m), followed by G4 (1258.83 m) variety. In interaction studies concerning filament length, there was no statistically significant difference in spacing and varieties. It was supported by Lalfelpuii et al. (2014) who reported a silk filament length of 1197 m by feeding V1 variety leaves to a double hybrid silkworm. Filament weight showed variation among plants spaced at different distances when fed to silkworms. Among these treatments, highest filament weight of 321.51 mg in 6 ft x 6 ft followed by 7 ft x 7 ft with 303.38 mg was recorded (Fig. 2). On comparing varieties, highest filament weight of 303.00 mg was recorded in V1 mulberry leaves fed to silkworm over the G4 (297.11 mg). With respect to the interaction of spacing and varieties, a significantly high value of filament weight of 324.46 mg was noticed in 6 ft x 6 ft, and a low value of filament weight of 271.45 mg was observed in 5 ft x 5 ft of G4. The present results are in correspondence with Thangaroja et al., (2018).
Notably higher denier of 2.45 was recorded in 6 ft x 6 ft among treatments (Fig. 2). This was followed by 7 ft x 7 ft (2.30), which was found to be on par with 5 ft x 5 ft (2.16). Regarding varieties, the maximum denier was found in V1 (2.37) and G4 (2.23), which were statistically comparable to each other. In the interaction between them, 6 ft x 6 ft had a high value of denier of 2.56, which was found to be superior to all other treatments. The present results confirm those of Anusha and Bhaskar (2018), who reported a denier of 2.28 when feeding V1 variety leaves to double hybrid silkworms. The observations regarding renditta was found maximum in 6 ft x 6 ft (6.88 kg) compared to 7 ft x 7 ft spacing (Fig. 2). By giving V1 variety, 6 ft x 6 ft (6.98 kg) recorded statistically high renditta compared to 7 ft x 7 ft (6.82 kg), 5 ft x 5 ft (6.58 kg). By giving G4 leaves, 6 ft x 6 ft (6.79 kg) recorded statistically high compared to 5 ft x 5 ft (6.34 kg). In interaction studies concerning renditta, there was no statistically significant difference in the spacing and varieties. This is by the results of Rao et al., (2004), who recorded 7.75 kg renditta by feeding V1 variety leaves to the double hybrid silkworm.
