INTRODUCTION
Everything that is desired in any breeding program is genetically development and productive and economical characteristic progress to increase the product, reduces the production costs and finally increases the profits of producers. This goal in country sericulture is significantly palpable. In sericulture various economic characteristics in each step are considerable.
Introducing hybrids with proper genetic potential in multiple economic characteristics
along with increasing sericulture income will insure this industry development.
Silkworm variety is the most important item in silkworm industry and it is considered
as key factor in egg quality determination and directly affects the silkworm
quality (Zhao et al., 2007). Among the basic
principles of genetics and eugenic methods we can mention to hydro vigor usage
phenomena as one of the main strategies eugenic that has great role in reaching
new and high production hybrids.
Ashoka and Govindan (1994) has studied 4 double cross
hybrid performance obtained from varieties and tested their 10,000 Larvae cocoon
weight, cocoon weight and its shell weight, silk shell percent and fibers length
and researchers found that double cross hybrids have better performance. In
another research Rao et al. (1997) express after
surveying some features of multiple pure silkworm variety and related hybrids,
multiple multi generation lines have lower weight than pure mono generation
lines in cocoon weight. Ksham et al. (1995) with
heritability analysis of few traits found that above traits has high heritability
in domain of 0.48 up to 0.64 and traits related to the stability and competence
has lower heritability in domain of 0.18 up to 0.25.
Bhargava et al. (1993) studies indicates that
heritability of larval period, cocoon shell weight, fibers length, larval weight
and larvae weight are very high. Also there was average heritability (<0.7),
cocoon production (0.65) and cocoon shell percent (0.7) which was observed and
indicates that these two traits are under environmental effects. Malik
et al. (1999) and Sing et al. (1998)
also in their researches reach to same results Ashoka and
Govindan (1990) stated that cocoon weight traits and shell weight has shown
high genetic progress and high heritability. Obtained results confirm effect
of increasing genetic influences on above traits. This is while the average
heritability oriented to the high level along with the slow genetic progress
for cocoon shell percent shows that these traits are controlled by genes posses
increasingly traits. Silkworm pure line crosses with each other lead to gaining
a superior power of hybrids than parents in cocoon production and other productive
traits. For these purpose extensive surveys has implemented on the hybrid power
in silkworm (Kobayashi et al., 1968; Rao
and Sahai, 1990). High percent of productive traits Heterosis can be explained
by estimating the additive genetic variance and non additive of cocoon traits.
In contrast non additive genetic variance has lower role in phenotypic appearance
of resistance traits that is larvae death and pupa survival percent and it is
expected that mentioned traits are less affected by the heterotic influence.
Cocoon traits are of the most important economical traits of silkworm and due
to high heritability (40-50%), direct selection performance on them is very
high (Mirhosseini et al., 2007).
In a research performed by Vishkaee et al. (2008)
it was clear that heterosis percentage of cocoon shell shows the lowest amount.
So that for some hybrids heterosis is negative. Overall, the heterotic effect
of cocoon shell weight and coccon weight is more than cocoon shell percent (Sing
et al., 1990; Malik et al., 1999).
Previous studies indicate that native x Chinesehybrid average heterosisis more
than native x Japanese hybrid average heterosis (Sing et
al., 1990; Vishkaee et al., 2008). Totally
native silkworm types of Iran has high general combining ability rather than
modified types which currently are used for commercial silkworm production.
So with regard to special combining ability and high heterosis of modified types
hybrids and also native ones, possibility of native type usage in breeding programs
can exist (Vishkaee et al., 2008). In quantitative
traits, genetic correlation and heritability are considered along with each
other (Sing et al., 1998; Seidavi
et al., 2007).
The correlation between traits results from polytropy. Gene’s linkage
on a chromosome also leads to short time correlation. About silkworm (Sing
et al., 1998) argue that more case selecting for more eggs depends
on pupa’s weight. But pupa’s weight must not be very high because
it will lead to genetic progress reduce. These scientists said that correlation
beyond female pupa weight and laying in pupas with high weight reduces.
Sing et al. (1998) said that pupation rate traits
and cocoon weight was affected by high dominance and both of them were affected
by epistasis. Also pupation rate is under cytoplasm effects. Different researchers
has reported laying trait heritability, larvae weight, larval period length,
growth rate, cocoon weight, pupa’s weight, shell’s weight and finally
silkworm cocoon percent in silkworm. In silkworm breeding traits correlation
also has very high importance. Research results indicate that laying correlation
with cocoon production power is negative. Produced cocoon amount correlation
with survival was positive and laying correlation with female pupa weight is
positive and laying correlation with butterfly weight is positive too (Ghanipoor,
2003; Seidavi et al., 2007). Kumar
et al. (1995) shows that there is high correlation between cocoon
weight traits, cocoon shell weight and also cocoon weight and cocoon shell percent.
Jayswal et al. (2000) and Sofi
et al. (1999) reported high genetic correlation beyond cocoon traits.
Ksham et al. (1995) reported high positive genetic
and phenotype correlation between total cocoon production and individual cocoon
weight. They also reach to same results between cocoon shell weight traits and
silk fiber length and expressed that selection for fiber length and Diner has
positive effect on cocoon production increase (Seidavi et
al., 2007). Until now these commercial hybrids of silkworm performance
has not been compare and there is no precise and academic information about
production performance degree and there is no meaningful or meaningless difference
between performance and production features.
Therefore, this research purposes contains some important performance indexes estimating in commercial silkworm hybrids in Iran and surveying the performance and superior hybrid selection with regard to different quantitative and qualitative features to produce and provide the superior hybrids. Since there is some new silkworm hybrids in silkworm research center of the Iran, performance of these hybrids must be studied.
MATERIALS AND METHODS
The research location was placed in Iran Silkworm Research Center in Rasht, Pasikhan village in Guilan province of Iran. The implementation steps of this survey were performed in spring of 2008. In this experiment, eggs of eight commercial silkworm hybrids, including hybrids of 104x103, 103x104, 32x31, 31x32, 154x151, 151x154, 154x153 and 153x154 as a treatment in the form 4 repeats was used and every repeat was involved 50 larvae hybrids. This experiment was performed to study the productive and economical traits of these commercial hybrids and introducing the superior hybrid.
Silkworm’s egg related to each one of these hybrids was taken from Iran
silkworm research center. Silkworm eggs were stored under situation such 25°C
and 80-75% humidity in hatching room for 12 days. After hatching, every hybrid
was breed separately and under standard situations. Breeding in young silkworm
period was performed by chopped leaves and paraffin paper coverage and in the
adult period it was performed with leaves and branches. In cocoon webby stage,
Mabshi will be used separately for each repeat. After larvae to pupa stages
complementation within the cocoons (7 days after starting to webby stage), cocoon
collecting and clean of each repeat was started. After breeding step, cocoons
were categorized into 4 groups named, the best, the middle, the double and the
low groups and after every determination of each group percent, complete shell
and cocoon all the best cocoons of the repeats were weighed. Studied traits
will involve alive larvae and pupa number, pupa vitality percent, produced cocoon
number, best, middle, low and double cocoon number and percent, male and female
cocoon weight, male and female silk shell weight, double cocoon weight, total
produced cocoon weight, 1000 larvae cocoon weight, larval period, time needed
for Mabshi of all the larvae, produced cocoon amount from 10,000 larvae within
4th instar and produced cocoon amount of each egg box. Different records of
studied traits entered into the Excel. Then data received from computer and
were statistically analyzed with SAS software. This experiment was performed
in a completely randomized frame with 8 treatments (which are hybrids) and for
repeat and within every repeat there were 50 larvae. Averages were compared
with Duncan multi domain test. Statistical model was as follow:
Where:
| Yijk |
= |
Record or observation |
| H |
= |
Average traits |
| Hi |
= |
ith hybrid effect |
| Rk |
= |
Rth repeat |
| Eijk |
= |
Other factors effect |
After evaluating and comparing average traits in Duncan method and providing
SD (Standard Deviation) experimental data to detect the superior hybrid it is
utilize from evaluation index method and sub-ordinat function (Mano
et al., 1993; Rao et al., 2006). Used
formula is as follow:
Where:
| A |
= |
Mean of particular trait in a hybrid |
| B |
= |
Overall mean of particular trait in total hybrids |
| C |
= |
Standard deviation |
| 50 |
= |
Fixed value |
| 10 |
= |
Standard unit |
Formulas used in the method under transverse function were as follows (Gower,
1971):
Xu = (Xi-Xmin.)/(Xmax-Xmin.) |
Where:
| Xu |
= |
Sub ordinate function |
| Xi |
= |
Measurement of trait of tested breed |
| Xmin. |
= |
The minimum value of the trait among all the tested hybrids |
| Xmax |
= |
The maximum value of the trait among all the tested hybrids |
From total obtained numbers of these two methods, at the end by using defined
formulas in excel, total evaluation index method and total sub ordinate function
were used for introducing superior hybrid.
RESULTS AND DISCUSSION
Results of this experiment are shown in Table 1-4
and Fig. 1-61. In fresh larva weight trait
in beginning of 1st instars, in studied hybrids to levels of performance were
observed, hybrids 32x31 and 31x32 and 154x151 and 151x154 that significantly
(p<0.05) with high performance level have placed in low performance level
along with other hybrids showed differences. In larva weight in beginning of
2nd instars 103x104 significantly (p<0.05) has the highest performance while
this hybrid in larva weight in beginning of 1st instars was in low level.
Hybrids 31x32, 104x103 and 154x151 have shown middle performance in terms of
numerical that there is no significant deference between them and others. Between
hybrids 32x31, 151x154, 153x154 and 154x153 there is no significant difference
in this trait. In larva weight in beginning of 3rd instars hybrids 103x104 and
104x103 have highest weighty in this trait (0.02675 g). There is no significant
difference between these two hybrids with hybrids 31x32 and 32x31 and 154x151
(p>0.05). Hybrid 104x103 had the highest record in larva weight in beginning
of 4th instars (0.16650 g) which in this trait had no significant difference
with hybrids 151x154, 153x154 (p<0.05). Studying results in larva weight
in the beginning of 5th instars indicates that there is no significant difference
between hybrids 103x104, 104x103 (p>0.05). But this trait amount in hybrid
103x104 was different with others (p<0.05). Hybrid 103x104 in larva weight
in the finishing of 1st instars had the highest record in this trait but it
did not significant difference with hybrid 31x32. Between these two mentioned
hybrids and hybrids 32x31, 104x103, 151x154 and 154x151 there were no significant
difference (p>0.05). But all of these hybrids have shown highest performance
rather than two hybrids 153x154 and 154x153 (p<0.05). Hybrid 103x104 revealed
highest record in larva weight in finishing of the 2nd instars (0.28 g). Despite
this difference there were no significant difference between this hybrid and
hybrids 31x32, 32x31,104x103, 151x154 and 154x151 (p>0.05). Hybrid 154x153
was at the lowest record in this trait (0.2375 g) which showed significant difference
along with 31x32, 103x104, 104x103 and 151x154 (p<0.05) but it did not has
significant difference with other hybrids (p>0.05). By evaluating this survey
results in larva weight in finishing of the 3rd instars we found that hybrid
103x104 had the highest record (0.156 g) that despite of being different in
numerical value it did not have significant different with hybrids 31x32, 32x31,
151x154, 154x151 (p.0.05).
| Table 1: |
Evaluation index points based on individual traits |
 |
|
| Table 2: |
Evaluation index points based on total traits |
 |
|
| Table 3: |
Sub-ordinate function points based on individual traits |
 |
|
| Table 4: |
Sub-ordinate function points based on total traits |
 |
|
|
| Fig. 1: |
Comparison of larva weight in beginning of 1st instar trait
in studied hybrids |
|
| Fig. 2: |
Comparison of larva weight in beginning of 2nd instar trait
in studied hybrids |
|
| Fig. 3: |
Comparison of larva weight in beginning of 3rd instar trait
in studied hybrids |
|
| Fig. 4: |
Comparison of larva weight in beginning of 4th instar trait
in studied hybrids |
|
| Fig. 5: |
Comparison of larva weight in beginning of 5th instar trait
in studied hybrids |
|
| Fig. 6: |
Comparison of larva weight in finishing of 1st instar trait
in studied hybrids |
|
| Fig. 7: |
Comparison of larva weight in finishing of 2nd instar trait
in studied hybrids |
|
| Fig. 8: |
Comparison of larva weight in finishing of 3rd instar trait
in studied hybrids |
|
| Fig. 9: |
Comparison of larva weight in finishing of 4th instar trait
in studied hybrids |
|
| Fig. 10: |
Comparison of larva weight in finishing of 5th instar trait
in studied hybrids |
|
| Fig. 11: |
Comparison of larva gain in 1st instar trait in studied hybrids |
|
| Fig. 12: |
Comparison of larva gain in 2nd instar trait in studied hybrids |
|
| Fig. 13: |
Comparison of larva gain in 3rd instar trait in studied hybrids |
|
| Fig. 14: |
Comparison of larva gain in 4th instar trait in studied hybrids |
|
| Fig. 15: |
Comparison of larva gain in 5th instar trait in studied hybrids |
|
| Fig. 16: |
Comparison of larva gain in 1-5 instar trait in studied hybrids |
|
| Fig. 17: |
Comparison of best cocoon number trait in studied hybrids |
|
| Fig. 18: |
Comparison of best cocoon percentage trait in studied hybrids |
|
| Fig. 19: |
Comparison of fresh best cocoon weight rait in studied hybrids |
|
| Fig. 20: |
Comparison of dried best cocoon weight trait in studied hybrids |
|
| Fig. 21: |
Comparison of pupae vitality percentage in best cocoon trait
in studied hybrids |
|
| Fig. 22: |
Comparison of middle cocoon number trait in studied hybrids |
|
| Fig. 23: |
Comparison of middle cocoon percentage trait in studied hybrids |
|
| Fig. 24: |
Comparison of fresh middle cocoon weight trait in studied
hybrids |
|
| Fig. 25: |
Comparison of dried middle cocoon weight trait in studied
hybrids |
|
| Fig. 26: |
Comparison of pupae vitality percentage in middle cocoon trait
in studied hybrids |
|
| Fig. 27: |
Comparison of low cocoon number trait in studied hybrids |
|
| Fig. 28: |
Comparison of low cocoon percentage trait in studied hybrids |
|
| Fig. 29: |
Comparison of fresh low cocoon weight trait in studied hybrids |
|
| Fig. 30: |
Comparison of dried low cocoon weight trait in studied hybrids |
|
| Fig. 31: |
Comparison of pupae vitality percentage in low cocoon trait
in studied hybrids |
|
| Fig. 32: |
Comparison of double cocoon number trait in studied hybrids |
|
| Fig. 33: |
Comparison of double cocoon percentage trait in studied hybrids |
|
| Fig. 34: |
Comparison of fresh double cocoon weight trait in studied
hybirds |
|
| Fig. 35: |
Comparison of dried double cocoon weight trait in studied
hybrids |
|
| Fig. 36: |
Comparison of pupae vitality percentage in double cocoon trait
in studied hybrids |
|
| Fig. 37: |
Comparison of total produced cocoon number trait in studied
hybrids |
|
| Fig. 38: |
Comparison of total produced cocoon weight trait in studied
hybrids |
|
| Fig. 39: |
Comparison of total produced fresh cocoon weight trait in
studied hybrids |
|
| Fig. 40: |
Comparison of alive larvae number trait in studied hybrids |
|
| Fig. 41: |
Comparison of pupae vitality percentage in total cocoon trait
in studied hybrids |
|
| Fig. 42: |
Comparison of male fresh cocoon weight trait in studied hybrids |
|
| Fig. 43: |
Comparison of male dried cocoon weight trait in studied hybrids |
|
| Fig. 44: |
Comparison of male fresh shell cocoon weight trait in studied
hybrids |
|
| Fig. 45: |
Comparison of male dried shell cocoon weight trait in studied
hybrids |
|
| Fig. 46: |
Comparison of male fresh cocoon percentage trait in studied
hybrids |
|
| Fig. 47: |
Comparison of male dried cocoon percentage trait in studied
hybrids |
|
| Fig. 48: |
Comparison of female fresh cocoon weight trait in studied
hybrids |
|
| Fig. 49: |
Comparison of female dried cocoon weight trait in studied
hybrids |
|
| Fig. 50: |
Comparison of female fresh shell cocoon weight trait in studied
hybrids |
|
| Fig. 51: |
Comparison of female dried shell cocoon weight trait in studied
hybrids |
|
| Fig. 52: |
Comparison of female fresh cocoon percentage trait in studied
hybrids |
|
| Fig. 53: |
Comparison of female dried cocoon percentage trait in studied
hybrids |
|
| Fig. 54: |
Comparison of fresh cocoon weight trait in studied hybrids |
|
| Fig. 55: |
Comparison of dried cocoon weight trait in studied hybrids |
|
| Fig. 56: |
Comparison of fresh shell cocoon weight trait in studied hybrids |
|
| Fig. 57: |
Comparison of dried shell cocoon weight trait in studied hybrids |
|
| Fig. 58: |
Comparison of fresh cocoon percentage trait in studied hybrids |
|
| Fig. 59: |
Comparison of dried cocoon percentage trait in studied hybrids |
|
| Fig. 60: |
Comparison of 10,000 larvae fresh cocoon weight trait in studied
hybrids |
|
| Fig. 61: |
Comparison of 10,000 larvae dried cocoon weight trait in studied
hybrids |
Performance of hybrids 153x154 and 154x153 in this trait was significantly
lower than mentioned hybrids (p<0.05). Hybrid 104x103 had the highest record
in larva weight in finishing if the 4th instars. Despite this conflict there
was no significant difference between this hybrid and hybrids 103x104 and 31x32
(p>0.05). In this trait between hybrids 31x32, 32x31, 151x154, 154x151, 153x154
and 154x153 despite of the numerical value difference there were no significant
difference (p>0.05). This research results about larva weight in finishing
of 5th instars indicated that there were no significant difference between hybrids
31x32, 32x31, 103x104, 104x103 (p>0.05). But this trait amount in these hybrids
were significantly higher than hybrids 151x154,154x151, 153x154 and 154x153
(p<0.05).
Larva gain in 1st instars in hybrid 103x104 was significantly higher than other
hybrids (p<0.05). Between hybrids 32x31, 104x103 and 154x151 there were no
significant difference in this trait (p>0.05). This research results showed
that there were no significant difference between hybrids under study in larva
gain in 2nd instars (p>0.05). In this research it was revealed that larva
gain in 3rd instars in hybrids 104x103, 153x154 and 154x153 was significantly
lower than other hybrids (p>0.05). Hybrid 104x103 in larva gain in 4th instars
had the highest record (0.614 g) which was significantly higher than hybrids
31x32, 154x151, 153x154 and 154x153 (p<0.05). Larva gain in 5th instars in
hybrids 31x32 and 32x31 was significantly higher than hybrids 151x154, 154x151,
153x154 and 154x153 (p<0.05). Larva gain in 1-5th instars in hybrids 31x32,
32x31, 103x104 and 104x103 was significantly >4 other hybrids (p<0.05).
In this study we found that best in traits as cocoon number and best cocoon
percentage between hybrids there were no significant difference (p>0.05).
Hybrids 32x31 and 104x103 were significantly higher than 151x154 and 154x151
in fresh best cocoon weight trait (p<0.05). Between other hybrids in this
trait there was no significant difference. Dried best cocoon weight in hybrid
104x103 was significantly higher than hybrids 151x154 and 154x151 (p<0.05).
Between these hybrids and other ones there were no significant differences.
In trait of Pupa vitality percentage in best cocoon despite numerical value
difference there was no significant difference between hybrids (p>0.05).
Middle cocoon number and middle cocoon percentage in hybrid 154x153 was significantly
higher than hybrids 31x32 and 31x32 (p>0.05). Between these hybrids with
103x104, 104x103, 151x154, 154x151 and 153x154 there were no significant differences
(p>0.05).
Experiments results in fresh middle cocoon weight shows that hybrid 154x153 was significantly higher than 32x31, 103x104, 154x151 (p<0.05). Between all of the mentioned hybrids along with hybrids 31x32, 104x103, 151x154 and 153x154 there were no significant difference (p>0.05). In dried middle cocoon weight between 8 evaluated hybrids there was no significant difference (p>0.05). Pupa vitality percentage in middle cocoon in hybrid 31x32 was the highest record which had significant difference with 154x151 (p<0.05). Beyond other 6 hybrids there were no significant difference (p>0.05). In two traits of low cocoon number and low cocoon percentage hybrid 151x154 had the highest negative record (with mean of 9.775) had significant difference with hybrids 31x32, 32x31, 104x103 and 154x153 (p<0.05). Fresh low cocoon weight in hybrids 151x154 has shown higher performance than 31x32, 32x31, 103x104, 104x103, 154x151 and 154x153 (p<0.05). Between 31x32 with 153x154 in this trait there were no significant difference (p>0.05). Dried low cocoon weight in hybrid 151x154 beyond studied hybrids had the highest record (2.195 g). This hybrid significantly indicated higher mean than hybrids 31x32, 32x31, 103x104, 104x103, 153x154 and154x153 (p<0.05). Hybrids 31x32, 32x31, 103x104, 104x103, 153x154 and 154x153 had no significant difference in this trait (p>0.05). Pupa vitality percentage in low cocoon in hybrid 154x151 was significantly higher than 31x32, 32x31, 103x104, 104x103 and 154x153 (p<0.05). But it did not have significant difference with hybrids 153x154 and 151x154 (p>0.05).
Double cocoon number and double cocoon percentage beyond eight hybrids did not have significant difference (p<0.05). Fresh double cocoon weight in hybrid 103x104 was significantly higher than 31x32 and 104x103 (p<0.05). But it did not have significant difference with others (p>0.05). Dried double cocoon weight in hybrid 103x104 was significantly higher than 104x103 (p<0.05). But it did not have significant difference with other hybrids (p>0.05). Pupa vitality percentage in double cocoon was the highest in the hybrids 31x32, 32x31, 153x154 and 154x153 (100%) which was significantly higher than 31x32, 32x31, 103x104, 151x154 and 154x153 (p<0.05). But they did not have significant difference with 103x104 and 153x154 (p>0.05). Despite of numerical difference in total produced cocoon number there were no significant differences between hybrids (p>0.05). Total produced cocoon weight in hybrid 104x103 was significantly higher than 151x154 (p<0.05) but it did not have significant difference with others (p>0.05). Hybrid 104x103 in total produced fresh cocoon weight was significantly higher than 151x154 (p<0.05). But it didn’t have significant difference with others (p>0.05). This study revealed that hybrid 103x104 in total produced dried cocoon weight was significantly higher than 154x151 (p<0.05). Between other hybrids in this trait there were no significant difference (p>0.05). In total alive larvae number there were no significant difference (p>0.05).
In pupa vitality percentage in total cocoon there were no significant difference (p>0.05). Hybrid 104x103 in male fresh cocoon weight has showed higher performance than 31x32, 151x154, 154x151, 153x154 and 154x153 (p<0.05). Experiment results in male dried cocoon weight were equal to male fresh cocoon weight. About 2 hybrids 32x31and 104x103 in male fresh cocoon shell weight was significantly higher than 31x32, 151x154, 154x151, 153x154 and 154x153 (p<0.05). In this trait between hybrids 31x32, 151x154, 154x151, 153x154 and 154x153 there were no significant difference (p>0.05). This study showed completely same results in male fresh cocoon shell weight with male dried cocoon shell weight. Male fresh cocoon percentage was significantly higher in hybrid 32x31 than 31x32, 151x154, 154x151, 154x153 (p<0.05). In this trait there were no significant difference between 31x32, 103x104, 104x103 and 153x154 (p>0.05). Male dried cocoon percentage in hybrid 32x31 had the highest performance than 151x154, 154x151 and 154x153 (p<0.05). Hybrids 31x32, 32x3, 103x104, 104x103 and 153x154 had no significant difference (p>0.05).
Female fresh cocoon weight in 154x153 was significantly lower than 31x32, 32x31, 103x104 and 104x103 (p<0.05). But this hybrid did not significant difference with 151x154, 154x151 and 153x154 (p>0.05). This experiment indicated that performance of 8 hybrids was completely same in two female fresh cocoon weight and female dried cocoon weight so that hybrid 153x154 was significantly lower than hybrids 31x32, 32x31, 103x104 and 104x103 (p<0.05) whereas between 154x151, 151x154 and 154x153 were not significantly differences (p>0.05). Hybrid 154x153 in female fresh cocoon shell weight was lower than hybrids 31x32, 32x31, 103x104, 104x103, 153x154 (p<0.05). Female fresh cocoon percentage in hybrid 153x154 was significantly higher than 154x151 and 154x153 (p<0.05). In this trait between 31x32, 32x31, 103x104, 104x103, 151x154 and 153x154 were no significant differences (p>0.05). Female dried cocoon percentage in 8 studied hybrids did not have significant differences (p>0.05).
Fresh cocoon weight in 104x103 was significantly higher than 151x154, 154x151,
153x154 and 154x153 (p<0.05). Between hybrids in dried cocoon weight, fresh
cocoon shell and dried cocoon shell weight despite of difference in numerical
value there were no significant difference (p>0.05). This study showed that
fresh cocoon shell percentage in hybrids 31x32, 32x31, 103x104, 104x103 and
153x154 has no significant differences (p>0.05). Hybrid 154x151 was significantly
lower than them (p<0.05). Dried cocoon shell percentage in hybrids 32x31
mL 04x103 and 153x154 was significantly higher than 154x151, 154x153 (p<0.05).
Hybrids 31x32, 151x154 and 154x153 has no significant differences in this trait
(p>0.05). This experiment results showed that in 10,000 larva fresh cocoon
weight between hybrids 31x32, 32x31, 103x104, 104x103, 154x153 there were no
significant difference (p>0.05) but hybrids 32x31 and 103x104 shown higher
performance than 151x154 and 154x151 (p<0.05). Experiment results in 1000
larva dried cocoon weight completely equal with 10,000 larva fresh cocoon weight.
Genetic objects evaluating also helps to determine special features like web
length, fluoride stability, stability towards illness, etc. (Li
et al., 2001) reaching to different genetic strains has provided
extensive approaches for producers in selecting the main parents which they
are intended. Even half of the eggs that are in suitable genetic groups can
potentially turn the silkworm researches to the mush extended domains (Arai
and Ito, 1967; Chandrashekharaiah and Babu, 2003).
In recent experiments there were attempts to determine and evaluating the polyvoltine
type features based on index evaluating method and sub ordinate function statistical
method that often is used to evaluate different hybrids of different silkworms.
Type evaluating leads to determine the genetic capability of different group
strains of silkworm to economical utilization.
Since features and specifications related to the silkworm were studied in different
climates there is regular evaluation of available types to have suitable usage
and the gained data and information will be useful for future breeding (Rao
et al., 2006). After 1905 that Toyama in Japan stated the positive
heterosis effect for silkworm hybrids, important egg producer countries started
to breed and modify the parent’s basis (Chinese and Japanese lines) and
market their hybrids. Various reports shows that many of quantitative traits
of silkworm has heterotic effect and therefore silkworm hybrids have the highest
performance in traits than parents. To produce commercial parent hybrids (P)
there is a need of two reproduced within variety steps. Therefore producer companies
first breed silkworm eggs 3 and 2p and then produce silkworm P. Hybrids and
their parent basis are constantly under evaluating and if necessary research
projects are performed to make new varieties (Ashoka et
al., 1993). In a research accomplished by Rao with the name of evaluation
of silkworm genetic capability of polyvoltine type and parent worm determination
for breeding programs, it studied 21 types of oval cocoon and 10 types of Dumbbell
it was revealed that beyond 21 species of oval silks, all of them were flat
except type APM19 that there were some signs on silkworm back. But cocoons of
this type have different colors such as white, yellowish gray, yellow and these
cocoon seeds were very soft, middle and hard. Between studied traits, fertility
of their oval types was 438 up to 567 and mean number of their fertility was
474 times. The lowest cocoon product (1000 larva weight produced silk) in AMG1
(8.836 kg) and its highest one was categorized in 28APM with mean product of
10.85 kg. In all of the species; pupa vitality was recorded >80% except in
type 1 AMPG (72.55%) and 11APM (76.73) and its mean vitality was 86.40%. The
highest cocoon pure weight was 26 APM and 1.412 g and its lowest APMW12 was
1.199 g and its mean was 1.312 g. Tallest web length to APM11 with 996 m and
its shortest was 28APM 604 m. Maximum raw silk 11APM was 13.03 and its minimum
was 20 APM 10.48%.
In all oval types, silk week capability was observed >70% (Rao
et al., 2006). In this experiment based on performed categorization
qualitative features of types were evaluated according to different parameters
such as fertility, production, pupation amount, cocoon weight, cocoon shell
weight, shell portion, web length, raw silk, (percentage) silk week capability
and cleanliness by using the index evaluating method and sub ordinate function
and then after this act it was obvious that between hybrids under study there
is significant difference which was like the research in this manner and its
detail is as follow. Various evaluating has been done to best determination
and the best strain assessment in which they could provide silkworm breeding
programs (Raju and Krishnamurthy, 1993; Rao
et al., 2006; Zanatta et al., 2009).
With this purpose in mind, its necessary that all of features related to silkworm
in each step of its life period be under study. During silkworm various life
cycle, environmental features affect on the produced silk worm quality (Ohi
et al., 1970; Zanatta et al., 2009;
Hannia et al., 2009) also more extended researches
are needed to improve economical goals and these researches improve new strains
during breeding programs which its goal was improvement of silk performance
(usage), concordance with external environment and ability to bear and stability
against illness (Yokoyama, 1979; Sen
et al., 1999; Li et al., 2001; Zanatta
et al., 2009).
Other studies related to using the performance usage (Miyagawa
and Sato, 1954; Marco et al., 2005; Zanatta
et al., 2009) and apparent differences (Aagaard
et al., 2002; Pilgrim et al., 2002;
Dujardin and Le Pont, 2004; Zanatta
et al., 2009) that indicates better strains for breeding in terms
of product. Cocoon external features that are related to its shape are strongly
depends on silkworm strain origin. Chinese strains have white school body and
forms an oval cocoon while Japanese strains have colorful school body and its
shape looks like oval (Zanatta et al., 2009).
All studied strains here are polyvoltine which are very resistance against
climate changes and produce less silks than the Polyvoltine strains (Rao
et al., 2006; Seidavi et al., 2008;
Zanatta et al., 2009). Vigor hybrid is an important
factor in increasing the cocoon production, evaluation and formed lines stability
by sibling worms and suitable intercourse determination for commercial productivity
(Nagaraju et al., 1996; Ghanipoor
et al., 2007; Ramesha et al., 2009).
That according to silks features importance produced from hybridization were
suitably improved and evaluated by silkworm breeders. Some of them have long
time production and just a few of them had short time production.
The main problem of manufactures was priority of worm important trait ordering
to improve their life. However, finding important factors that are responsible
for worms surviving are very important for silkworm breeders. The most important
goal of worm breeding is matching and synchronization of new genotypes with
more coordination in various climates and also selecting more stable bonding
than silkworm to commercial productivity (Ramesha et
al., 2009). Also it is found that most of the genetic features in silkworm
are under multi gene control and under affect of environmental factors and nutrients
same as other systems. Therefore, in the entire researches hybrid compounds
are breeding in same conditions and are feed with similar species of leaves
to be evaluated with important quantitative traits in hybrid performance analysis.
The main goal of silkworm breeders is using silkworm hybrids with stable level
of profitability in silk production and improved cocoon production (Kovalov,
1970; Ramesha et al., 2009).
The goal of silkworm breeding is not only combine and intercourse new genotypes
but also is to determine the stable silkworm hybrids to have commercial productivity
by farmers. Suitable parent worm selection and information about nature and
the gene performance value and important economical traits can increase production
successfulness (Chouhan et al., 2000; Ramesha
et al., 2009). Assessment and evaluation about current combination
in insects breeding is one of the necessary prerequisites to shim the combining
way of most desired features available in various genotype in one hybrid intercourse,
of course parent breeding is usually is not good reflection of capabilities
combination but however helps to breeders to determine related parent relations
nature and also next generation nature (Ramesha et al.,
2009).
Polygenic status results in stability or vitality in pupa products (Pallavi
and Basavaraja, 2007). Also polygenic in bivoltine hybrids causes more vitality
than monovoltine hybrid in bad environmental conditions that is because of the
variability gene formation beyond the communities (Watanabe,
2002; Pallavi and Basavaraja, 2007). Furthermore
facility in breeding and better growth power and economical improvement leads
better results than monovoltine hybrids (Kumar et al.,
1998; Mal Reddy et al., 2005; Pallavi
and Basavaraja, 2007). So current research based on suitable basis selection
to improve bivoltine hybrids to industrial productivity (Pallavi
and Basavaraja, 2007).
CONCLUSION
After evaluating data with two used statistical method to compare productive and economical trait performance of height commercial studied hybrids these results were determined according to simple evaluating index, hybrids151x154 with 4063.799 scores gained the highest rank and after that hybrid 32x31 was placed. Hybrids 103x104, 154x153 also gained the lowest ranking. According to sub ordinate function hybrid 32x31 with 43.13057 gained the highest ranking. Hyhbrids151x154 also gained the lowest ranking. According to this experiment results hybrid 32x31 has the higher potential performance beyond other ones and its use is recommended.
ACKNOWLEDGEMENTS
This manuscript is obtained from M.Sc. Thesis of Ehsan Vaez Jajali at Islamic Azad University, Karaj Branch, Karaj, Iran. Researchers are grateful to the Iran Silkworm Research Centre (ISRC) for providing silkworm data. This study was supported and financed by the Iran Silkworm Research Center (ISRC) mainly. Researchers thank Mr. Mavvajpour, Mrs. K. Taieb Naeemi and Mr. Y. Kheirkhah for technical assistances.
