Silvia Cappellozza
Sericultural Specialized Section of Padua - Experiment
Institute for Agricultural Zoology of
Florence - Ministry of Agricultural and
Forestry Policies - ITALY
15 December 2002
Sericulture in Italy originated in an imprecise period of time between the 10th and 11th century. The silkworm rearing was probably introduced by Arabs to Sicily and by Byzantines to the other regions of the South. Nevertheless, it is not possible to exclude that in the peninsula other development centres of the sericultural activity there had been, due to the contacts with Oriental people. Certain bibliographical indications date the beginning of sericulture in Bologna to the 13th century and to Trieste (13th-14th centuries) (Bertelli Bergamaschi, 1994). Sericulture continued to flourish in almost all the Italian regions until the Second World War. At the same time, the industry of egg production had been spread in the whole Italian peninsula until the middle of the 20th century. Each Italian region, where sericulture represented an economic activity, had its own silkworm strains (or geographical races), which belonged to silkworm eggs producers; these races were adapted to live and produce in the particular environmental conditions where they had always been reared. Their phenotype was homogeneous enough with regard to the cocoon colour and shape. However, they had not been subjected to a precise selection; very often, more races with similar characteristics were bred with the idea of ameliorating and making them resistant to diseases. Moreover, workers of the silkworm egg production centres sometimes mixed them unintentionally. For this reason, an accurate analysis of their cocoon colour and shape would have revealed different shades and nuances.
With the gradual closing of the silkworm egg production centres the races were transported to the Sericultural Stations of Ascoli and Padua (SSSP). Here the selection of old races has been started in 1918; new races were first described in 1926-27 (Lombardi, 1964). In 1964 there were 98 races or strains evolved from the old races (Lombardi, ibid.). To these, 27 races, which were a gift, from the Institute for Zoology of the Pavia University, were added. Some races, obtained during the long work of breeding and selection, which were particular mutants, were regarded only as a scientific curiosity and for this reason eliminated. In fact, at that time, only races with a remarkable silk production were judged as valuable for preservation; moreover, the funds available for the Institute's routine activities (such as germplasm maintenance) have always been limited, so that it was impossible to conserve all the mutants. Another problem was the preservation of bivoltine and mostly polivoltine strains. Originating in tropical zones, they carry out more than one generation per year. Their maintenance has always been difficult due to the vegetative behaviour of the mulberry in the Northern Italy climatic conditions. In fact, during the winter, the polivoltine larvae could be fed only if mulberries had been put in a heated greenhouse to produce leaf also with low external temperatures. For this reason, annual layings were selected from the egg mass, and the characteristic "diapausing eggs" prevailed, also if it was not the original characteristic.
After 1964, the work of selection was continued but with a reduced budget, so that reproduction of strains, rather than new creation, was the major activity. In 1978 the last Italian egg production centre (S. Giacomo di Veglia - TV) closed and the Chinese and Japanese lines, which were used in order to produce the polyhybrid commercial eggs, were given to the SSSP to be preserved. These Chinese and Japanese lines had been imported some years before from Japan; they are very well-known strains in Japan, but once in Italy, other names were attributed to them, so that nowadays is quite impossible to find out the original ones. During the 1980s other lines and strains had been eliminated, due to the scarcity of the SSSP staff and the continuous decrease in funds. A serious problem arose, starting with 1989, caused by an Insect Growth Regulator (fenoxycarb), which is distributed on fruit crops and pollutes the mulberry leaves, and resulted in the accidental loss of some races. In fact, this chemical prevents silkworm spinning and larval transformation into pupae and adults, interrupting the metamorphic process. Countermeasures were taken in the following years to deal with this major constraint (see later).
Recently some other strains have been imported through the National Silkworm Rearers Association from India (1), from Turkey (4 lines) and from Japan (6 lines). Two strains have been imported from Albania, thanks to scientific contacts with local sericulturists. The original polivoltine Nistaari strain has been obtained from France, and re-imported to Italy for genetics research, because the Nistaari strain currently in conservation is monovoltine as a result of previous selection. This strain is being used to obtain transgenic silkworms with the technique of RNA-interference, which can be considered the creation of a new race with particular features.
Currently there are about 130 silkworm strains and pure lines preserved in the SSSP. They can be grouped as follows:
Yellow peanut shape cocoon (indigenous races): 9
Golden cocoon Chinese races: 2
White cocoon (indigenous races): 7
White strains selected by Mari: 7
Strains selected until 1964: 4 with coloured cocoon; 5 with white cocoon.
Polyvoltine races: 3
Chinese and Japanese strains imported before 1964: 5
Strains received by the Institute for Zoology "Spallanzani" (Pavia): 7
Lines received from the egg production centre closed in 1978: 40
Strains of uncertain origin: 18
Strains evolved from recent crosses: 4
Lines imported from Turkey (1995): 4
Strains from Albania (1997): 2
Lines imported from Japan (1997): 6
Nistari transgenic lines (Rnai of gene per): 7
For the complete list see annex 1. As it is possible to understand a part of the preserved germplasm is important for its genetic features, a part for its commercial utilization for silk production.
The germplasm is reproduced once per year, mostly in the springtime rearing on mulberry leaf. The mulberry leaf is collected in the mulberry field of the SSSP. However, due to the above-mentioned leaf pollution by the Insect Growth Regulator (IGR) fenoxycarb, which occurs mainly in May-June (the same season of spring rearing), non-polluted leaves are transported to the SSSP from Calabria by refrigerated trucks to carry out the fifth instar (the silkworm's most sensitive period to the IGR). A small-scale rearing on leaf, from the irrigated parcels of mulberry field, is performed in September-October. A small-scale rearing is also carried out on artificial diet during February-March. The rearing on the artificial diet has been carried out for three years (from 2000) on about twenty strains and has the aim of studying long-term effects of artificial feeding on silkworm races; the diet is produced by the SSSP itself on the basis of a specifically studied recipe. To ensure the conservation of the strains also in case of failure of the artificial rearing, the same strains reared on artificial diet during the spring season are reared also in September-October on mulberry leaf.
Some anticipation in time of leaf production is obtained by covering a part of the mulberry field with tunnels. Furthermore, a heated greenhouse, which contains mulberry plants in pots, is used to produce leaf to use from the end of March to the end of April. Leaf anticipated production is useful to rear the first instars of bivoltine and polivoltine strains, in order to terminate rearing before August in the case of bivoltine and to spare artificial diet in the case of polivoltine.
Every year morphological controls are performed on egg, larva and cocoon features to observe the conformity to the racial standards. Commercial parameters such as cocoon weight, cocoon shell weight and silk percentage are recorded every year. Furthermore, reeling of single cocoons from the mass is carried out for a part of the lines. Polyhybrid eggs (usually four ways) are prepared from the lines for experimental aims in springtime and late summer and reared every year and compared to imported polyhybrid eggs. Pebrine inspection is carried out (single moth inspection) for all the races and lines, while 6-12 moths are inspected together in case of polyhybrid production.
Facilities for larval rearing are one thermostatic room (relative humidity, temperature and photoperiod under control), two thermostats, one room where temperature is controlled and several rooms where heaters work and maintain the apt temperature during springtime and September-October. Three refrigerated rooms are used for egg hibernation. One autoclave and a microwave apparatus are used to cook artificial diet. A reeling device for single cocoon thread evaluation is available.
One technician, one permanent worker and three seasonal workers carry out rearing under the supervision of the Director (currently Dr. L. Cappellozza); while two-three workers provide leaf for larval feeding.
Contact details: Dr. Luciano Cappellozza, Sezione Specializzata per la Bachicoltura di Padova, Via dei Colli, 28 - 35143 Padova - Italy. Telephone number: +39 049 620205; Fax number: +39 049 623119; e-mail: [email protected]; [email protected]
The management of the germplasm collection has become very difficult due to the problem of spring pollution by fenoxycarb. This active ingredient (a.i.) is contained in one insecticide sprayed in orchards to fight against Lepidopteran pests. Although the danger represented by the chemical for sericulture is clear and it has been demonstrated that it acts at very low doses (ng) on silkworms Cappellozza et al, 1990), it has taken years to prohibit its use in all the Italian regions and actually it is used illegally, as controls are not very strict. The effect on the silkworm is the non-spinning syndrome, which has been recorded in the whole of Northern Italy and also in France since 1989. Long-term effects on wild Lepidopterans and other animals are not well-known. Due to this situation, sericulture has almost disappeared from Northern Italy. The period when the insecticide is distributed and persists on crops ranges from the middle of May to the end of June. Unfortunately it is the best period to reproduce the silkworm germplasm; before this period the mulberry does not produce, apart from greenhouse plants, and afterwards the climate it is too hot and humid to successfully rear races, some of which are particularly delicate and subject to diseases. For this reason, it was decided to bring the leaf every year from Southern Italy (Calabria, where apple, pear and peach cultivations are not very popular) to Padua by refrigerated trucks to carry out the last part of reproduction rearing. In fact, only last instar larvae are very sensitive to the chemical, so rearing of first four instars is performed with the SSSP leaf. Two to three trucks of leaf are necessary in order to rear all the races, so the maintenance cost is very high. On the other hand, trials of rearing at the end of the summer (September) were also performed. It has been demonstrated that is difficult to rear all the races in autumn, due to the fact that only a small part of the mulberry field is irrigated and the leaf quality is not very good. Furthermore, climatic conditions are not indicated for all the races and diseases spread largely in this period.
Shifting a relevant part of germplasm reproduction from leaf feeding to artificial diet could be the way to overcome this difficulty and, for this reason, studies are in progress, to know the effect of long-term artificial rearing on the silkworm germplasm maintenance. The problem is that not all the strains are apt to be reared on artificial diet; therefore, selection of the races and amelioration of the diet are needed. In the framework of the project "New technologies for the re-launch of Italian mori-sericulture" good results have been obtained with regard both to race selection for adaptation to artificial diet and to artificial diet improvement to meet particular strain needs.
Furthermore, techniques to obtain silkworm egg hatching all the year long (with or without hydrochloric acid treatment) have been studied in depth, to be ready to face up to any problems or difficulties.
Current problems in management of germplasm strains are: 1) the limited space that does not permit the rearing of all the strains together (usually rearing is divided into two turns with an interval of fifteen days between hatching of the first lot of germplasm and the second one); the lack of space could affect the quality of rearing, causing involuntary confusion among different strains; 2) the limited funds available results in a limited staff; seasonal workers are often inexperienced so that they can cause involuntary confusion and damage and, however, they slow down the work; furthermore, genetic improvement of the biological material is very scarce, because the selection work is very long and demanding and more workers would be necessary to perform it; 3) the old building where the SSSP is located makes it difficult to properly carry out disinfections and to prevent spreading of silkworm diseases.
With regard to germplasm utilization, until now the major objective has been the production of polyhybrid eggs to distribute to farmers or to public agencies in order to develop sericultural activities. Mutant strains have been used for particular purposes (scientific studies) or as curiosities to show in exhibitions or for didactic aims. Nowadays, due to the low price of the raw silk, which does not justify rearing for silk production in Italy, alternatives uses of the silkworm are being studied as for the mulberry. Lyophilised larvae powder seem to be important in the cure of diabetes; larvae could be used as food source for human beings or animals with particular needs; transgenic larvae could produce proteins of pharmaceutical interest and so on. The first alternative use of the germplasm has been the utilization of polyhybrid eggs, originating from strains apt to be fed on artificial diets, to make didactic kits to be distributed in the primary school.
As above-mentioned, under the framework of the project "New technologies to re-launch Italian mori-sericulture", different studies are in progress to develop the germplasm collection. The first important step, already obtained, is to select strains apt to grow on artificial diet. It has been recorded that this goal is very easy to reach for lines of Japanese origin, less easy for indigenous strains and very difficult for lines of Chinese origin, which, on the other hand, are important in order to make the crosses with Japanese lines to obtain polyhybrid eggs. Furthermore, it is also a remarkable target to select strains apt to be reared on artificial diet with a mulberry leaf low content, because of the cost of the leaf powder. Also this result has already been obtained, since in the SSSP germplasm collection there are lines that thrive on this kind of diet, especially during the last instars.
Apart from the method of traditional selection, new prospects for the development of the germplasm collection are offered by non-traditional techniques such as transgenesis. Efforts are in progress, and the first transgenic lines were obtained one year ago. The polivoltine strain Nistaari was chosen to carry out the experiment and a construct, which should cause RNA interference for the gene per, was integrated in the germinal cells of a female moth. The construct also carries the reporter gene GFLP (Green Fluorescent Protein), which makes transgenic individuals identifiable under a microscope equipped with a UV lamp. From the moth progeny different lines were isolated and reproduced; now their characterization is in progress. Because of the fact that the per gene is one of the genes involved in the regulation of the endogenous clock of the insects, the developmental cycle of the larvae could be affected being reduced in time (as in Drosophila melanogaster). This fact could have important effects on the economy of silkworm rearing. On the other hand, demonstrating that RNAi works in the Bombyx is an important goal per se. In fact, ideally, the expression of some genes could be disrupted, obtaining different kind of mutants useful for scientific studies or for commercial aims.
One researcher on the SSSP staff has always been in charge of the database management of the silkworm strains. After 1964, when the available information on the SSSP silkworm strains was collected and organized by Lombardi in the Annals, observations have been written in registers and passed on by different persons, who had in turn the responsibility of studying and controlling the silkworm germplasm. Notes had been hand-written and only since 1990 a computer database has been organized. The language used is the Italian and no translation into English is provided. The database is updated every year and images of eggs, fifth instar larvae and cocoons are enclosed with the description of each strain. Nevertheless, much information remains to be added as well as experimental data regarding studies on particular aspects of strain behaviour (for example: acceptance of artificial diet).
Since updating and translating into English the database on SSSP silkworm strains is a real need, a three-year plan has recently been presented to the Ministry as part of the SSSP ordinary activity, which will include the database revision and its publishing on the Web with a link to the SSSP website. Also a translation into English will be provided. The methodology is as follows: first of all gathering additional information on the strains of the silkworm germplasm bank and elaborating the data collected in the project "New technologies for the re-launch of Italian sericulture"; then, selecting further images which can be useful to describe the strains; afterwards, deciding the kind of format to use or drawing a new format apt to be quickly consulted on the web; eventually translating the database into Italian and English and in html with the purpose of publishing it. The FAO proposal regarding an international database on the silkworm is regarded as an integration of this activity and a chance of exchanging opinions with other experts of sericulture.
Currently the descriptor used for the silkworm strains derives from the catalogue of the SSSP silkworm germplasm collection already mentioned with regard to the above-quoted paper by Lombardi (1964). However, that catalogue had been studied to highlight the productive characteristics of the silkworm strains with regard to the silk, which was considered the most interesting derivative from the silkworm. Nowadays, if alternative uses of the silkworm should be considered, additional voices should be included.
Furthermore, some voices are not precise. For example, the length of the life cycle is determined in springtime in a heated room (around 25°C). It is clear that the shown datum is an average between the duration of the life cycle in different years, because climate has a great influence on this parameter; in fact, if the rearing room does not have a thermostatic regulation, the temperature can easily vary by 2-3°C according to external temperature. Another example regards the cocoon and silk shell weight; according to the number of feedings per day and the quality of leaf administered to the larvae this parameter may widely vary. In fact, the data are different according to different years and seasons; they have a relative value, because e.g. they may be used to compare lines for polihybrid production among them.
Although the data have these serious limitations, an example of germplasm directory or stock catalogue now in use in the SSSP follows.
STRAIN "TG 10"
Historic traits: "TG 10" is a breed coming from a cross of two strains spinning yellow cocoons. Originally there were two different strains: "TG10 long thread" and "TG 10 small eggs". The strain currently preserved is called only "TG 10". In the past, the larva was masked.
Notes: the larva shows some difficulties in changing the cuticle during the moults.
Morphological traits
1) Larva:
First instar: the larva is brownish at its hatching. Then, the thorax becomes light grey and the abdomen brownish-grey.
Second instar: the thorax is light grey, the abdomen brownish.
Third instar: the thorax is light grey, the abdomen is light grey with dark grey pigmentation. Crescents are easily distinguishable.
Fourth instar: the larva is greyish, without mask, crescents are not more easily distinguishable.
Fifth instar: the larva is white, without mask, crescents are absent or not easily distinguishable. Yellow haemolimph. Monovoltine.
2) Cocoon: lightly constricted in the middle, small, peach yellow in colour, pale in the outer cocoon's layer, dark yellow in the inner layers. The adult is often unable to emerge from the cocoon since it is weak (so it is convenient to cut the cocoon in order to make the emergence phase easier).
3) Moth: White, black eyes.
4) Eggs: pink-greyish in colour. Scarce deposition.
Quantitative traits
1) Length of reelable silk thread: not available.
2) Titer: not available
3) N. cocoons/kg: 1, 064
4) N.cocoons/liter: not available
5) Cocoons size (diameter): not available
6) Length of life cycle: hatching-spinning: 31 days; spinning-emergence: 17 days (springtime)
The silkworm resources, differently from almost all the other animal genetic resources, cannot be found in nature, but only in germplasm banks. These germplasm banks, which are located in different countries with a sericultural tradition suffer from the same problems all around the world; scarcity of funds and of staff who are involved in preservation, reproduction and development of new mutants and selected strains. The governments of industrialized countries are not particularly interested in giving funds for maintenance and research in a field that does not produce any more remarkable incomes. On the other hand, developing countries may be interested in the sericultural activity, but do not have available germplasm resources to produce silkworm eggs. The aging of the scientists involved in the sericultural research and the lack of young people interested in a field of research poor in funds, make the problem of maintenance more acute at least in Europe and Japan. Pollution by pesticides and other chemicals in industrialized countries contributes to endangering silkworm germplasm resources. For all these reasons the only way to preserve and maintain this important genetic resource in different countries is to make it known and appreciated both by public opinion and by scientists in different fields of research, who can use the silkworm as an interesting experimental tool. The promotion of global sharing of germplasm information is certainly the first step in this way. Promoting collaboration and international projects among Institutes is the next step to take.
Sharing common information in the case of the silkworm is probable easier than in the case of the mulberry; in fact, a common language has been already coded and genetic loci responsible for mutations are known in many mutants. Furthermore, also DNA sequences of some genes have been discovered. However, there are some difficulties; as in the case of the mulberry, some strains are known under local names in different countries, also if they are the same or originating from the same strains; some races or lines have been probably mixed with others due to organization problems or to the inexperience of temporary workers and it is difficult to come back to their original characteristics. Some parameters, although they are the same as those used to describe the races everywhere, can differ in their interpretation or have a scarce applicability to different places and environmental conditions. As previously written, for example, the silk production by a strain can be greatly affected by the mulberry variety used to feed it, by the method of cultivation of the mulberry plants (irrigation, fertilization...), by the number of feedings per day...Furthermore, if it were possible to reach an agreement to standardize the method, a huge work of re-definition and re-evaluation of each germplasm bank would make the collection of homogeneous information very expensive and time demanding
To overcome, at least partially, these problems, the establishment of a Working group may be a pre-requisite. This group should make some decisions and, first of all, the participants should agree on the way to write the catalogue. In a first phase, probably non-completely homogeneous descriptions from different countries should be accepted, at least with regard to quantitative characteristics. This catalogue should contain all the information useful to identify strains and races, but it should not give too much information. Members of the Working group should keep in contact by e-mail, for all the time necessary to draft a plan; however, the group should be open to the criticism of other experts and listen to the needs of different final users. The final proposal of the Working group could be evaluated by FAO and changed according to suggestions from all the parties involved.
In addition, conciseness is important when the information is put on the Web, to make downloading easier for users. For the same reason, in my opinion, it is advisable to avoid uploading of images in this first phase. Another important point is the English translation; usually most technicians know the scientific terms useful to illustrate the strains and races and this knowledge may be sufficient to draft a minimum descriptor; however, translation must be provided by FAO in case experts have not familiarity with English. Furthermore, before publishing on the Web, a critical revision should be carried out by some of the members of the Working group, to ascertain if linguistic and scientific standards have been fulfilled. Eventually, the Working group should work on the name of silkworm races. Some spelling errors in translation from one language to another could be corrected and probably in this way the number of different races could be reduced.
The database could be linked to the websites of the Institutes where the silkworm germplasm is conserved, so that the users can obtain more information about the particular mutants they are interested in, directly asking to the responsible scientist.
As in the case of mulberry, DNA analysis of the strains may be useful to identify the more similar among them or to decide if some of them are even identical. However, a particular obstacle in carrying out this kind of study is represented by the fact that there is not a free circulation of the silkworm strains among the Institutes, because of restrictive laws emanated many years ago, when the sericultural activity was very important for the economy of the developed countries.
Also in the silkworm catalogue particular characteristics of the strains, which make them useful for alternatives uses other than silk production, should be indicated.
Updating of the database should be forecast from the beginning and the Working group may be in charge of this duty. Electronic conferences, held at fixed intervals of time, could be the means to inform all the scientific community involved in the silkworm research about new findngs and FAO could have an active role in the promotion and organization of this kind of events.
As in the case of the mulberry, global sharing of information could help to establish contacts and links between Institutes and could result in an easier exchange of germplasm. However, in my opinion, at the beginning this exchange will be limited only to those strains that have a mere scientific interest (particular type of mutants) and it will not regard strains that can have a commercial exploitation (pure lines to produce polyhybrid). Furthermore, it appear easier to organize exchanges among Institutes (a strain in exchange for another strain), while requests for strains to Institutes by private companies or public institutions, which are not involved in germplasm maintenance, might be unsuccessful. It should be remembered that often the Institutes receive funds from their Governments only for the silkworm germplasm maintenance so that distributing and duplicating the strains/lines may result in decreasing the available budget or also in giving a good reason to Authorities to close the Institutes, which are sometimes evaluated as unproductive. In this way a valuable treasure of genetic biodiversity will be lost forever.
As I have also explained in the case of the mulberry, in my opinion germplasm information on the Web will not be used directly by farmers or extension workers. In fact, even if PC facilities, Internet usage and English knowledge were largely spread all around the world and even in the developing countries, it could not be possible that farmers look at the descriptors as a catalogue from which they can order what they need. Also technicians (extension workers) probably do not have the sufficient scientific knowledge to choose from a list the right strain/race for a particular zone and situation.
The problem is complicated by the fact that usually polyhybrid larvae are reared by farmers, while rearing races is more difficult because they are delicate and very sensitive to diseases. Polyhybrids can be produced only in limited quantity by Institutes, which do not have the possibility and the organization to commercialise them.
My point of view is that sharing of information could help to carry out co-operative research among Institutes in different countries (including developing ones) and the results of this research could be exploited in order to give advantages to farmers. Extension workers and technicians could ask the Institutes to address the research in order to solve particular practical problems, which arise from their daily experience. E.g. if it could be interesting to obtain chrysalides for human or animal feeding and if cutting the silk cocoon was an obstacle to rationalizing the industrial activity, final users could urge the research Institutes to select strains with naked pupae and to give the parental lines to the egg production centres for the commercial exploitation of the laboratory research. As in the case of the mulberry, germplasm information could also be interesting also for private companies which may fund research on the silkworm races. Obviously, in this case, patents will be used to protect the newly selected or ameliorated strains, but Government Authorities could intervene to regulate the final price of silkworm eggs to farmers. Another possibility is that farmers are paid better to rear strains that have final utilizations different from silk production (e.g. cosmetic or pharmaceutical uses); in this way the germplasm information shared by the Institutes and the knowledge of the potentiality of the silkworm germplasm bank by the private sector could be utilized to create an extra-value of goods with benefits for farmers. Complete production chains could be established, where companies give eggs to farmers and collect the final product, assuring a good income to silkworm rearers. To reach this goal, in my opinion, the database should not be a mere list of strains understandable only for people who are sericulturists, but should highlight possible utilization and suggest studies to carry out about each single strain. Moreover, once again, I want to highlight the importance of updating the database with the results, also if partial, of the research in progress all around the world.
1) TG 10
2) Varo
3) Brianza
4) Abruzzo
5)
Romagna
6) Romagna bis
7) Almeria
8) B
9) Giallo Grecia
10)
Alpe
11) - (lost)
12) AP
13) - (lost)
14) O.208
15) -
(lost)
16) AP 11
17) B.14 b
18) Bianca Italia
19) Novi
20) -
lost
21) Bagdad
22) BS 16
23) GB 408
24) 280 M
25) 772 M
26)
190 M
27) 120 M
28) 10 M
29) 441 M
30) 351 M
31) SA 48
32) PL
24
33) PL 20
34) 21 Malucelli
35) SA 15
36) SA 67
37) PL
22
38) Cinese B bava lunga (CHBL)
39) SA 105
40) Nistaari
41)
Awojiku
42) Icot
43) Gialla 9/496
44) 175 FA
45) Verde
cinturato
46) Verde ovale
47) Gibbosi
48) Albini
49) Sejaku green
bg
50) Nemor III
51) Noupei
52) Orgosolo
53) Dominante cioccolato
bb
54) Polivoltina melanica
55) BC 2
56) BC 17
57) BC 20/I
58) BC
20/II
59) BC 21
60) BC 22/I
61) BC 23
62) BC 24
63) BC 25
64)
BC 26
65) BC 27
66) BC 28
67) BG 1/II
68) BG 1/III
69) BG
2
70) BG 5/I
71) BG 8/I
72) BG 20
73) BG 24
74) BG 28
75) BG
35
76) BG 36
77) BG 37
78) BG 38
79) BG 40
80) BG 41
81)
KG
82) IG
83) UC
84) RC
85) NC
86) CC SG
87) YC
88) TC
BB
89) TC BG
90) R 33
91) - lost
92) RC 33
93) RG 35
94) RG
36
95) R 3 G
96) Oro gigante
97) Dom cioccolato bs (treotto)
98)
Japkino verde
99) B uova rosse
100) B uova gialle
101) B ceppi uova
trasparenti
102) Han Han
103) Rosa
104) 199 LS
105) Arancio
106)
R9 Neri BP
107) Nistaari PG uova trasparenti LB (larve bianche)
108)
Nistari PG uova trasparenti LV (larve verdi)
109) Giallo B
110) Treotto
Rosa
111) BO
112) 628 Scanalato
113) SA 48 larve bianche
114) Razza
indiana
115) Originata da C60 × Rosa
116) Originata da SA1 × R9
neri (LB)
117) Originata da SA1 × r9 neri (Larve rigate)
118) 10
turca
119) 14 turca
120) 15 turca
121) 28 turca
122) Cinese
I
123) Cinese II
124) SC I
125) SC II
126) SC III
127) SG
I
128) SG II
129) SG III
130) Nistaari transgeniche: 7 linee
Bertelli Bergamaschi, M. 1994 Seta e colori nell'alto Medioevo. Il Siricum del Monastero bresciano di San Salvatore. Milano, Italy, Cisalpino ed.,.459 p.
Cappellozza, L., Miotto, F., & Moretto, E. 1990 Effetti del fenoxycarb a basse concentrazioni sulle larve di Bombyx mori (Lepidoptera Bombycidae). Redia, LXXIII (2), pp. 517-529.
Lombardi, P.L. 1964 Patrimonio nazionale di razze di B. mori non più in uso nell'industria (conservazioni-selezioni). Annuario della Stazione Bacologica Sperimentale "E. Verson" di Padova, vol.52, pp. 235-261.
