Mulberry germplasm database, maintained at SES-Vratza contains data for the main qualitative and quantitative characters values for most of accessions. Now the data for the mulberry germplasm are translated in English and converted to electronic files.
It is necessary and very essential to create a software for integrated database and descriptor preparation as well as query based program for mulberry genetic resources in order to upload them in Internet.
Characterization of germplasm is essential to identify the individual genotypes which collectively indicates the extent of variability which exists among the accessions and to compare with each other for further investigation and utilization. The characterization is also a process in which highly heritable characters are subjected for systematic data recording which finally helps in identifying the different germplasm. The comprehensive information on variability recorded helps the breeders for effective crop improvement. Enrichment of mulberry germplasm bank with high variability and the characterization of these resources is a continuous process for generating a strong data base.
The data about the accessions names, botanic name, the origin,the characteristic of the crown and the position of the branches toward the stem as well as the buds size, shape and color are presented in Table 3.(Petkov et al. 1994).
Since mulberry pruning at SES-Vratza is practiced once every year in the end of May/beginning of June the prevailing shape of mulberry crown is egg shaped(46%) followed by pile shaped (45%) and pyramid shaped crown. The results shown in the table manifest that 52 accessions have egg shaped crown, 51 accessions have pile shaped crown, and only 10 accessions have pyramid shape.
Other important character, characterizing the accessions is the position of the branches toward the stem.(Table 4) Only in accession N190 (“crying mulberry”, M. alba var. pendula) the branches growth angle is from minus 90° to +90 toward a horizontal plain. In the other accessions this angle varies from 0-25 to 90°. The size of the angle influences the shape and density of the crown.
In the mulberry gene bank there are buds of all sizes but the prevailing are with size from 2 to 5 mm. Most of varieties have triangular shape of the buds. A big diversity was detected regarding the buds color - from gray with different nuances to deep brown.
The data about the shoots, stipules, internodal distance and leaves position are presented in Table 4 and chart 4. It is evident from the table that most of the accessions have curved shoots. The distance between two neighboring leaves on one shoot is called internodal distance and is not only qualitative character but also a very important commercial trait determining the leaf yield by one tree or unit land. The value of this character is different in the different parts of the shoot, therefore it is measured in the shoot base part, middle part and the top part. The data from the middle part showed that most of the accessions had medium internodal distance (63%), followed by those with short internodal distance (31%).
With some small exceptions most of the accessions studied have alternative leaves position. In the phylotaxy grade, the mulberry accessions having grade 1/3 are prevailing, but there are some accessions with grades 2/5 and 2/7. This character is not very important because even at one tree the different shoots have different grade. Also the leaf position is hardly to be determined due to the absence of some buds on the shoot or because not all the buds sprout.
The characteristics of mulberry leaves are shown in Table 5 and chart 5. A characteristic trait of mulberry leaf is its lobation type. It is considered in moriculture that generally the varieties with unlobed leaves are more precious, however for complete evaluation a lot of characters should be taken into account.
Most of the accessions maintained at mulberry gene bank of SES - Vratza have unlobed leaves (83%). Some other varieties like P 6, P 10, P 17, P 21, Kairiu Ichinoze, Kairiu Nezumigaeshi, Kenmoshi, Chinso 2, Kairiu improved, Russian, Ukrainian 107, Florio, Jiacola, N106, Kokuso 70 and Kokuso 27 have different kind of leaves, namely together with the unlobed there are some lobed and deep lobed leaves. The highest percentage deep lobed leaves was detected in the Japanese varieties Kairiu nezumigaeshi, Kenmoshi and Chinso 2.
Most of the accessions manifested triangular and heart shaped leaves. The varieties having serrate leaf margin are prevailing. 21 mulberry accessions have rough leaf surface, 58 slightly rough and 34 are with smooth leaf surface. Most of the varieties have green leaf color - 59, followed by those with deep green color and only 14 have light green leaves. The varieties having rough (coriaceous) leaf texture which are more suitable for feeding the last instars larvae are prevailing - 67. For the young instars larvae feeding are more suitable the tender (chartaceous) leaf texture varieties - 43 numbers.
The data about the leaf size and the characteristics of leaf petiole are presented in Table 6, chart 6 and 7. The leaf length varies widely among the accessions studied. With small leaves are the varieties Saniish 7 - 9.48 cm and Kenmoshi - 9.67 cm, with medium size leaves are most of the varieties - 61, with semi-medium size - 50 and with very big size - only one, the Russian variety Pobeda.
The highest leaf length manifested the following varieties: Pobeda-20.82 cm, P 27-18.90 cm, N 59-17.82 cm, Digmuri-17.53 cm, P 11-17.49 cm, Kokuso 13-17.46 cm, P 26 - 17.42 cm, Kinriu - 17.33 cm and Azerbaidjan 20 - 17.31 cm. 17 mulberry accessions have leaf width from 6 to 9 cm, 78 accessions - leaf width from 9 to 12 cm, 17 - from 12 to 15 cm and 1 - leaf width more than 15 cm.
The highest leaf width was detected in the mulberry varieties Pobeda-15.76 cm, P 5-14.43 cm, Azerbaidjan 20-14.19 cm, P 27-13.76 cm and P 13-13.10 cm. Generally thick leaf, smooth in nature is desirable for silkworm rearing. Most of the varieties maintained at SES’ germplasm have comparatively thin leaves.
The accessions having acute leaf apex are prevailing-52, followed by those having caudate and acuminate leaf apex. In spite the leaf petiole characters are not economically important (excluding its length) they have very important place in the characterization of the variety.
In SES’ germplasm are prevailing the varieties with medium petiole length (from 3 to 5 cm)-82, followed by those with short petiole (up to 3 cm)-20 and with long petiole - 1. The shortest petiole length manifested the accessions N 26-1.83 cm and Kenmoshi-1.93 cm and the longest - Pobeda-5.20 cm, Firudin tut-4.67 cm, P 28-4.65 cm, Saniish 17-4.57 cm, N 186-4.40 cm Emin tut-4.36 cm, Tadjikian without seeds-4.36 cm, Kinriu - 4.25 cm, Pionerskii and Husan 3 with 4.20 cm petiole length.
The leaf petiole width varies from 1.7 mm in Saniish 6 to 4.20 mm in Pobeda, but most of the varieties have petiole width from 2 to 3 mm-76. The data concerning the reproductive characters of the mulberry accessions are presented in Table 7 and chart 8.
Most of the varieties are unisex (72 % female and 20 % male) and less are bisexual. Only 9 accessions are bisexual-P 13, P 19, Kokuso 20, Kokuso 27, Saniish 14, Husan 59, Jakubtut, Siuzisu and N 59. The female varieties are prevailing-82, therefore they could be used in the selection programs by hybridization.
From economical point of view in Bulgaria the male varieties which do not have fruits are more important because the fruits availability makes more difficult the pruning and stains the leaves, especially during the fifth instar larvae feeding period (beginning/middle of June).
There are 22 male varieties in the germplasm, namely P 5, P8, P19, P 21, Tbilisuri, Uzbekian, Husan 13, Armenia, Pionerskii, Saniish 6, Gruzniish 4, Gruzniish 5, Tbilniish 2, Digmuri, N 79, Zarif tut, Firudin tut, Azeri tut, Ukrainian 4, Ukrainian 107, N 26 and Lu.
The power of flowering detected was weak in 27 mulberry accessions, strong in 11 and medium in the prevailing 75 accessions. Most of the varieties have 3 racemes - 49 and 4 racemes - 44. The racemes length varies from 7 mm in the varieties P 21 and Siozisu to 35 mm in Uzbekian and the racemes width varies from 4 mm in Pionerskii to 18 mm in N 59. Usually the male racemes are bigger in size than the female.
The number of flowers in one raceme varies from 22 in the accessions P 1, P 7, P 13, Ukrainian 107 and Moretiana to 73 in Saniiish 15, but the varieties having flowers number in one raceme from 30 to 40 are prevailing.
The mulberry seed length is from 1.4 mm in Kairiu nezumigaeshi variety to 2.8 mm in Husan 3 and Gruzniish 7. The seed width varies from 1 mm in Siuzisu to 2.2 mm in Kairiu ichinoze, Shinso 2 and Azerbaidjan 20. The seed weight varies from 0.7 mg in Kokuso 20 to 2.5 mg in Russian and 2.6 mg in Azerbaidjan 20. However in the most of accessions the single seed weight is from 1.3 to 1.8 mg.
The data characterizing mulberry fruits are presented in Table 8, chart 9, 10 and 11. Depending on the fruit size and formation of more number of seeds, female parents are selected for breeding purpose.
The fruit length varies from 1.4 cm in Kartli to 2.64 cm in Kokuso 21. In most of mulberry accessions the fruit length is from 1.6 cm to 2.2 cm (79%). In most of the varieties the fruit width is from 1.2 to 1.3 cm (39%). The fruit weight varies from 4.08 g in P 13, 4.10 g in P 7 and 4.26 g in N104 to 29.32 g in P 6, 22.69 g in Kokuso 21, 18.76 g in Kutaguri, 18.52 g in Kenmoshi, 18.47 g in Kinriu, 18.00 g in Kokuso 27 and 17.93 g in Azeri tut. Most of the germplasm accessions have fruit weight from 8 to 16 g (68%).
The leaf yield by 1 tree, leaves percentage from the whole vegetation yield and the leaf annual yield per 1 ha mulberry garden have been studied by Petkov (1998) in 66 mulberry accessions from the genetic resources maintained at SES-Vratza.(Table 9,chart 12,13)
It was detected that there were clearly expressed variety differences regarding the mulberry productivity. The average leaf yield per one tree obtained was 6.21 kg and it varied from 4.54 kg in Kairio Ichinose to 8.11 kg in Emin tut variety. In most of the accessions studied the leaf yield per one tree is from 6 to 7 kg (40%). The highest variation was detected in the species Morus Alba and Morus Multicaulis.
Other important character influencing the mulberry productivity is the leaves percentage from the whole vegetation yield. Petkov (1998) detected that in 12 of the accessions included in the study the difference towards the mean was significant. The leaves percentage was higher than the mean in the varieties Tbilisuri, Georgia, Husan 1, Husan 39, Saniish 5, Shinso 2 and Siozisu.The most of mulberry varieties studied have leaf percentage higher than 50 %. The highest variation of this trait was detected in Morus Alba, Morus Kagayamae and Morus Multicaulis. Morus rubra is characterized with comparatively lower leaf percentage but Morus bombycis manifested very high leaf percentage.
The data regarding the leaf annual yield per 1 ha rainfed mulberry plantation manifested that 16 accessions had comparatively lower productivity-less than 10 t/ha. Other 7 accessions showed much higher productivity. Most of the accessions manifested a leaf yield per 1 ha from 10.50 to 12.00 t (62%).
The mulberry leaf biochemical composition was studied by Petkov (1998), using 13 accessions from the gene bank (Table 10, chart 14). He detected that the leaves of the mulberry varieties Husan 5, Firudin tut, Husan 1, Kartli and Digmuri contained significantly lower crude protein than the N 106 variety, used as control, but the varieties Uhvi, P7 and P9 manifested higher protein content in the leaves compared with the control. The results showed that the leaf dry matter in the varieties studied was from 27.12 % to 30.27 %, crude protein content-from 23.57% to 26.25%, the crude fats from 3.05 to 4.77% and the crude fibers percentage was from 10.59 to 12.40%.
The propagation characters were evaluated by Petkov (1995, 1998) (Tables 11, 12, 13, chart 15). It was detected the highest species variation regarding the phenological stages, namely the beginning of 1st -2nd leaf sprouting, 4th -5th leaves sprouting and flowering. The lowest variation showed the phenological stages beginning of bud swelling, fruit ripening, leaf yellowing and leaf fall. The necessary sum of the effective temperatures for mass bud swelling is 179 0 C. The duration of the whole vegetation period varied from 206 days in Morus latifolia to 216 days in Morus alba.
According to Petkov(1998) the minimum temperature necessary for the beginning of mulberry vegetation in the region of Vratza is 5oC. The necessary sums of the effective temperatures for the varieties of Morus alba are 1600C for buds swelling, 2360C for buds sprouting, 2710C for 1st -2nd leaves sprouting, 3330C for 4th -5th leaf sprouting, 3430C for flowering, and 6740C for fruit ripening.
Petkov (1998) studied the rooting ability in 36 mulberry varieties from the genetic resources maintained at SES-Vratza.(Table 14). He detected that the dry matter content in the cuttings varied from 63.35% in Saniish 14 variety to 77.49 % in P16. In 24 accessions the dry matter content was less than 70%.
The percentage of the cuttings having bark cracking was from 45 to 100%, the cuttings having beginning of root growing were from 70 to 100%. The percentage of the cuttings, having roots was from 0 in P 19 to 100% in P20 and Gruzniish 4 varieties. It was detected a high variation regarding the percentage of the cuttings, having roots in the accessions tested. Most of them had rooting ability from 40 to 60%, three accessions had less than 20% rooting, ten accessions like Vratza 1, Jakub tut, Ukrainian 9, Kinriu and Ichinose had rooting ability higher than 90 %.
From the above review the following conclusions could be made:
1. In the mulberry germplasm maintained at SES-Vratza there are accessions from nearly all countries dealing with sericulture from the temperate and sub-tropical climatic zone. Accessions from Bulgaria, Italy, Russia, Georgia, Japan, Armenia, China, Azerbaijan, Egypt, Uzbekistan and Ukraine are presented in the gene bank. Most of the mulberry varieties are indigenous and selected in Bulgaria.
2. In the mulberry germplasm are prevailing the varieties-branches-45, varieties- hybrids-35, followed by varieties -populations - 5 and varieties polyployds - 3.
3. Most of the varieties maintained have curved shoots with different degree of the curve. Regarding the phylotaxy grade, most of the accessions have 1/3 grade.
4. Most of the accessions studied have unlobed leaves, but 16 varieties have different lobation of the leaves. The biggest number are the varieties having leaves with rough (coriaceous) leaf texture. However 43 accessions are characterized with chartaceous leaf texture.
5. The length and width of the leaf vary in big limits. With small leaf size are the varieties Saniish 7 and Kenmoshi, with medium leaf size are most of the varieties-61, with semi-medium-50 and with very big-1(Pobeda).
6. Most of the mulberry accessions maintained are female-82, followed by 22 male and 9 bisexual varieties.
7. In most of the varieties the flowering has medium power, the racemes length varies from 7 mm in P21 to 35 mm in Uzbekian. The fruit length is from 1.4 cm in Kartli to 2.64 cm in Kokuso 21. The seed size is from 1.4 mm in Kairiu nezumigaeshi to 2.8 mm in Husan 3 and Gruzniish 7. The single seed weight is from 0.7 mg in Kokuso 20 to 2.5 mg in Russian.
8. In most of the accessions studied the leaf yield per one tree is from 6 to 7 kg. The most of mulberry varieties studied have leaf percentage higher than 50%. Most of the accessions manifested a leaf yield per 1 ha from 10.50 t to 12.00 t.
9. The leaf dry matter in the varieties studied was from 27.12 % to 30.27%, crude protein content-from 23.57% to 26.25%, the crude fats from 3.05 to 4.77% and the crude fibers percentage was from 10.59 to 12.40%.
10. The duration of the whole vegetation period varied from 206 days in Morus latifolia to 216 days in Morus alba.
11. A high variation regarding the percentage of the cuttings, having roots in the accessions tested was detected. Most of them had rooting ability from 40 to 60%, three accessions had less than 20% rooting. Ten accessions, including Vratza 1, Jakub tut, Ukrainian 9, Kinriu and Ichinose had rooting ability higher than 90 %.
12. The studies on mulberry germplasm at SES-Vratza should be continued and expanded to cover more characters such as peroxidase isozime profile, biochemical parameters (chlorophyll content;soluble protein content;soluble carbohydrate), molecular characteri-zation, tolerance/resistance to diseases.
13. It is necessary to create a software for integrated database and descriptor preparation and query based program for mulberry genetic resources in Bulgaria.
Sharing of mulberry germplasm information is very important not only for the countries, practicing sericulture but also for the countries using mulberry leaves as fodder for the domestic animals, mulberry fruits for food and other by-products for different purposes.
The main problems in the sharing this information are:
* Language-some countries, having comparatively rich mulberry genetic resources like those from the former Soviet Union (Ukraine, Uzbekistan, Azarbaidjan, Georgia) still have problems with communication in English.
* Lack of enough techniques for fast and easy communication - some countries still do not have internet, fax communication is difficult.
* In some countries mulberry genetic resources are not very well studied
* Lack of internationally accepted methodology for mulberry qualitative and quantitative characters characterization and evaluation.
In nowadays and in the near future the easiest way to share information about the mulberry germplasm for each country is by internet. For establishment of a successful system for internet uploading and sharing the mulberry germplasm information we suggest the following measures:
1. To establish under FAO and ISC a working group (committee), consisted of leading moriculturists, fluent in English from different countries, having mulberry germplasm resources.
2. The working group to develop a standard methodology for characterization and evaluation of mulberry germplasm.
3. Each country/organization/company which wants to share information for their mulberry germplasm and to receive regular information for the germplasm in other participating countries to be invited by FAO/ISC to prepare, following the standard methodology in electronic files in English a complete information about their mulberry genetic resources.
4. FAO to provide funding for creation of internet site with information about mulberry genetic resources of each participating country/organization/company and a common site for global mulberry germplasm.
Mulberry palnt is highly influenced by the soil and climatic conditions. One the same variety can give excellent results in one country or region but in other countries/regions the performance of the variety is bad. For example, one of the most popular mulberry varieties in Japan, namely Kairio Nezumigaeshi and Ichinoze do not give good performance in Bulgaria. The reason may be is that Bulgarian summer is drier than those in Japan. The same is the reason that one Japanese variety - Kinriu, which is not very popular in Japan gives excellent results in Bulgaraia- Kinriu is sensitive to bacteriosis during wet summer.
The tropical varieties are not suitable for the temperate climate countries like Bulgaria because they are very sensitive to cold weather in the winter. For example, in one introduced recently at SES-Vratza from Egypt variety (analogue of Indian Kanva 2) about 65-70 % of the shoots are frozen in the winter.
The international trade with mulberry planting material (cuttings or saplings) is not very common. Usually neighboring countries practice this trade due mainly to the difficulties with transportation to far distances.
In Bulgaria, the breeders rights are protected by a special law. Taking into account the above reasons generally the sharing of mulberry genetic resources between different countries would not be a problem. SES-Vratza is ready to share its mulberry germplasm with other countries by exchange on equivalent basis or against payment the saplings. We have already provided some mulberry varieties to Greece, Libya, Czech Republic, Yugoslavia, Ukraine and Egypt.
