THE PARENTAL EFFECT ON THE PROGENY BROOD POST-CAPPING STAGE DURATION

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1 PSZCZELNCZE ZESZYTY NAUKOWE Rok XL, Nr THE PARENTAL EFFECT ON THE PROGENY BROOD POST-CAPPNG STAGE DURATON Maciej Siuda, Jerzy Wilde Academy of Agriculture and Technology, Apiculture Division, Olsztyn, POLAND Summary The post-capping developmental stage (pes) of queens, drones and workers was determined. The queens with known pes were inseminated with sperm of one drone with a shorter or longer pes or with doses of 8 mm' mixed semen. The queens were kept in.kirchhainer" m~cs and the pes of the progeny of the crossing were determined. The correlation between the queens and their sons was highly significant (r= 0.54, p<0,01) but the correlation calculated between quee'ls and their queen daughters was only r= 0.29, p<0.07. The regression coefficient of the mother-queens on their daughters was b=0.78, and that of the' sons-drones was The estimated coefficients of the pes heritability amounted h 2 =0.6 for the daughter-queens and h 2 =0.45 for the sons. The correlation between the workers and their mothers and their drone fathers we re similary low (r=0.26 and r=o.28 respectively), but both were highly signiticant (p<0.01). According to these results queens have a greater intluence on the postcapping duration of their sons than on that of their daughters. The pes of the worker correlated significantly with that of both parents. Because of the low correlation coefficient, a rapid process of selection for low pes in workers, and the appearance of bees tolerating varroatosis because of this trait, appears unlikely. Keywords: breeding, selection, resistance, Va"oa jacobsoni, post capping period, correlation, heritability. NTRODUCTON Since 1991, the Division of Apiculture of University of Agricultural and Technnology in Olsztyn (NorthEast Poland) has been working on breeding out the honey be es with a short post-capping developmental stage (PCS). Attempts to obtain such bee strains are one example of work that has been carried out in order.o create bee lines resistant against Varroa jacobsoni. This kind of resistance against the parasite invasion was found to exist in South-African bee Apis mellifera capensis. ts workers emerge as early as days after the duration of the postcapping stage, and the still immature Varroa parasite progeny dies (M o r i t z, M a u t z 1990). t was supposed that a short period of the host's post-arval development * This research was supported by the KBN Grant Nr. :; S

2 would restrain the mite reproduction to only a direct reproduction level and therefore would enable us to limit or completely restrict the introduction of acaricides, which should thus not only free the honey-bee colonies from Varroa jacobsoni but also free the bee products from the remains of acaricide substances. n our Division, we have been breeding bees with a short PCS within the carniolan bee race, and also, in co-operation with The Apiculture nstitute of Oberursel (Germany), within hybrids of Apis mellifera capensis x Apis mellifera camica, crossing them back with carniolan drones. The L a n ge n b a c h method (1991) was most often used when selecting the worker be es for a short peso The time of cełł sealing of 60 cełłs on average was determinated by marking individual cells on a plastic sheet at ~-hrs intervals. Approximately 10 hrs before hatching, the cappings of these cells were marked by attaching numbered queen marking disk. By the time the worker bees emerged, celi capping had been removed. The marking disks feli through a grid attached to the bottom of the hive and through a tunneł on a circular register plate. This plate was subdivivided into 24 segments, and revolved once in 24 hrs. The time ot' emergence could be read from the position ot' the marking disks. The celi was identivied from the num ber on the disk, and the duration ot' the sealing period was caculated from the respective sealing time. n the conditions of NorthEast Poland, this procedure permits us to rear three generations of queens and their worker progeny but only two of them can be tested in the same season. New, more efficient methods are therefore desired. t appears that one possible way could be by establishing the correlation coefficients between the pes duration in the differenthoney bee castes. Such an approach could possibly enable us to avoid the time-consuming determination ot' workers' pes duration and ensure instead that we obtain five - six generations ot' queens annually. MATERALS AND METHODS The experiment was carried in the apiary of the Apiculture Division of the U niversity of Agricultural and Technnology of Olsztyn in n 1992, the carniolan honey bee race was used, and since 1993 its hybrids with Apis mellifera capensis (F 5 and the further generations), crossing them back with the carniolan drones. The queens were reared continuously in the queenless rearing colonies. The time of the queens pes duration was determined by the authors own method (W i d e 1994, W i d e and S i u d a 1992). The time of queen cełł sealing of all cells was determinated individual at 4-hrs intervals by inspection of rearing colonies. Approximately 10 hrs before hatching, the cappings of these queen cells in the incubator at l-h intervals were observed. Once emerged, the queens were introduced to 8

3 the newly settled smali mating hives (made of foamy polystyrene) and following two days of holding them in a cellar (temp. 10 C) they were placed in an api ary. The very moment of the comb's cells capping was detected by marking a sample of cells on a transparent plastic sheet. The duration of the workers pes was estimated using the method by L a n g e n b a c h (1991). As for drones, the authors own method was elaborated (W i d e and S i u d a 1992). A number of queens were inseminated with semen taken from one drones with known duration time for their pes, individually selected and different for each queen. The remaining queens with known pes were inseminated with semen of one drone with shorter ar longer PCS or with single dosis of 8 mm' mixed semen. The queens were kept in "kirchhainer" nucs and the PCS of the progeny of the crossing were determined. n 1992, the time of PCS duration was determined for 40 queens, 327 drones and 1300 workers of the camica F2 generation (tab. 1 and 2). Of this number, five queens started the regular oviposition following their insemination with the semen from an individually selected drone. n 1993 the pes durations were determined for 14 - daughter-queens of hybrid F6 generation, for 246 carniolan drones and for 128 workers, and in 1994 for 223 carniolan workers - the progeny of queens that had been inserninated with mixed semen. The results of these experiment, were statistically tested using the "Statgraphics" computer package procedure (D ą b k o w s k i 1992). RESULTS n 1992, the queens emerged between and hours, on average after hrs of the pes development, while the sons-drones between hrs, on average after hrs (tab. l). The correlation coefficients were calculated between the pes durations in the motherqueens and their progeny - daughter queens and sons (tab. 3). A moderate, however highly significant correlation was found between the mothers and their sons postlarval development time (r= 0.54, p<o.ol). Correlation coefficient for the mother- and daughter-queens was low (r= 0.29) and was at the margin of significance limits (p<0.07). The regression coefficient for mother andtheir daughter-queens on was b=0.78, and for mother and sonsdrones was The estimated coefficients of the PCS heritability was to h 2 =0.6 for the daughter-queens and h 2 =0.45 for sons (tab. 3). n 1992, the workers originating from queens inseminated with semen of a single drone emerged after to hrs, on average after hrs of the post-capping development (tab. 2). The correlation coefficients between workers and their mothers, and between workers and 9

4 their fathers were r=0.26 and r=0.28 respectively (tab. 3). Both the values were highly significant (p<0.01). The obtained regression coefficients were to b=0.33 and b=0.12 respectively, while the heritability coefficient were h 2 =0.37 for mother-queens and workers, and h 2 =0.24 for fathers and wórker bees. PCS duration in daughter-queens and sons (hours) Długość OCZ matek-córek i synów (w godzinach) Table 1 n range - rozstęp x daughter-queens 1992 matki-córki 1992 daughter-queens 1993 matki-córki sons - synowie n 1992, the workers, originating from queens inseminated with the mixed semen, had the PCS ranging from to 310 hours, on average hrs (n= 1088; tab. 2). The estimated correlation coefficient between the mother-queens and workers was r= and it was statistically significant (p<0.05) and that of heritability h 2 = 0.37 (tab. 3). Table 2 Workers' and drones'pcs duration in successive generations and years of experiment (hours) Długość OCZ robotnic i trutni w kolejnych pokoleniach i latach doświadczenia (w godzinach) range - rozstęp Generation n x Pokolenie workers - robotnice 1992 F workers - robotnice F _) workers - robotnice F 6 * drones - trutnie 1993 P workers - robotnice.t 994 Fj workers from mother-queens inseminated by a single drune * robotnice od matek unasienianych pojedynczymi trutniami 10

5 n 1993, the daughter-queens emerged between and 205 hours, on average 1R4.3 hrs after brood celi capping (tab. 1). The correlation coefficient between the PCS durations of the mother-queens and daughterqueens of the hybrid F6 generation was high (r= 0.73) and statistically highly sigrufieant (p<o.01), the regression coefficient of the daughter-queens on their mother was to b=3.51; whereas the heritability coefficient had been overestimated (h"> 1; tab. 3). Three queens from that F6 generation lai d eggs regularly after being inseminated with semen from an individually selected drone. n this case, the workers emerged between and hrs, on average hrs after brood celi capping. The correlation coefficient between the PCS ofworkers and their mother-queen was high to r= t was ais o high between the PCS of workers and drones orginating from the same queen to r= 0.97 (tab. 3). Both the last coefficients were, Table 3 Coefficients ot" regression (b). correlation (r) and heritability (h 2 ) Współczynniki regresji (b). korelacji (r) i odziedziczalności (lr') b r p h 2 mother-queens/daughter-queens 1992 matki/matki-córki p( mother-queens/daughter-queens 1993 matki/matki-córki 1993 mother-queens/drones 1992 matki/trutnie 1992 mother-queens/workers 1992 matki/robotnice 1992 mother-queens/workers 1992* matki/robotnice 1992* mother-queens/workers 1993* matki/robotnice 1993* mother-queens/workers 1994 matki/robotnice 1994 father-drones/workers 1992* ojcowie/robotnice 1992* father-drones/workers 1993" ojcowie/robotnice 1993* P ( p(o.o p( p( P ( P ( P( p( workers from mother-queens inseminated by a single drone. robotnice od matek unasienianych pojedynczymi trutniami 11

6 highly significant (p-cfl.ol ). The workers on their parents regressron coefficients were b= 1.03 and b= 1.75 respectively. The heritability coefficient of the mother-queens' PCS duration by workers appeared to be overestimated (h"> l), while for the parent-drones and workers it amounted to h 2 = n 1994, the workers ernerged after hrs, on average hrs after brood celi capping (tab. 2). The respective coefficients were of similar values in the case of the progeny of the rnother-queens inseminated in The correłation coefficient was low and negative r = However it was statistically significant (p<0.05), the regression coefficient of workers on their mothers was b= -0.19, and the heritability coefficient was to h 2 = 0.6 (tab. 3). DSCUSSON The heritability coefficients obtained in the year 1993 for the mother - daughter-queens, and for the workers and their mothers, was overestimated. The low genetic variation, estimated at 5.23%, was probably the cause of such results. n the years 1992 and 1994, the coefficient of correłation and regression for the workers originating from mother-queens inseminated with Smnr' of the mixed semen, were negative. n the remaining cases they were positive. The values of the cajculated coefficients for the workers originating from mother-queens in 1992 we re comparable to those obtained by B u c h l e r and D r e s c h e r (1990). The negative values.of the considered coefficients can point to evidence of the drones' considerable influence in determining the PCS in bees. M o r i t z and Jor d a n (1992) came to a similar concłusion. However, they obtained high er heritability coefficients (h 2 = 0.76) than those in our own experiment. The heritability coefficients estimated for workers in the 1992 season were simiłar to those reported by B u c h e r and D r e s c h e r (1990) and by L e C o n t e et al. (1994). n 1994, the coefficient obtained in our investigations was of simiłar value (h 2 = 0.6) to that reported by H a r b o (1992). The increase in the heritability coefficient value was accompanied by the investigated trait ranging towards the lower values and by the mean PCS value decreasing. Similarly to heritability coefficients evolved the remaining parameters estimated in our own experiment. This suggests that genetic factors are an increasing influence on the trait of the short duration of the capped brood period. t is, however, difficult to explain why, regardless of the high correlation and heritabiłity indexes, onły smali breeding progress, as concerns the seection trait, was achieved. Most probably, some impact on this situation exerts the rełatively smali number of the bred and sełection 12

7 individuals which is limited by the pes monitoring possibilities. Better results could possibly be obtained, using the estimated coefficients and changing the selection procedure. lt would be advisable to abandon the determination of the pes of each individual and in each generation and to concentrate efforts instead on breeding out and selecting the more numerous materiał. REFERENCES B li c h e r R., D r e s c h e r W. (1990) - Variance and heritability of the capped developrnental stage in EuropeanApis mellifera L. and its correlation with increased Varroa jacobsoni Oud. infestation. J.Apic.Res., 29: H a r b o J.R. (1992) - Breeding honey bees (Hymenoptera: Apidae) for more rapid development of larvae and pupae. J.Econ.Entomol., 85: D ą b k o w s k i L, (1992) - Statgrafics - System statystycznego opracowania danych. Komputerowa Oficyna Wydawnicza "Help", s. L a n g e n b a c h K. (1991) - Bestimmung der Zellverdeckelungsdauer verschiedener Bienenherkunfte. Apidologie, 22: L e C o n t e, B r u c h o u C; B e n h a m o u d a K., G a u t h i e r c., C o r - n u e t l.m. (1994) - Heritability of the queen brood post-caping stage duration in Apis mellifera mellifera L. Apidologie, 25: M o r i t z R.F.A., Jor d a n K (1992) - Selection of resistance against Varroa jacobsoni across caste and sex in the honeybee (Apis mellifera L.. Hymenoptera: Apidae). Exp.Appl. Acarol. 16: M o r i t z R.F.A., M a u t z D. (1990) - Development ol' Varroa jacobsoni in colonies Apis mełli/era capensis and Apis mełlifera camica. Apidologie, 21: W i d e l. (1994) - Hodowla pszczół o skróconym okresie postlarwalnym. odpornych na Varroa jacobsoni. Acta Acad. Agricult. Tech Olst., Zootechnica, 39B: W i d e J., S i u d a M. (1992) - Próba selekcji na skrócenie stadium czerwia zasklepionego u pszczoły miodnej Apis mellifera camica. Ann. UMCS. Sectio DD, 47: WPŁYW RODZCÓW NA OKRES CZERWU ZASKLEPONEGO POTOMSTWA M. S i u d a, J. W i d e Streszczenie Od roku 1991 prowadzone są w Zakładzie Pszczelnictwa AR-T w Olsztynie prace hodowlane prowadzące do wyhodowania pszczół o krótkim okresie czerwiu zasklepionego (OCZ). Poszukuje się nowych bardziej efektywnych metod selekcji. Wydaje się, iż jedną z nich może być zastosowanie współczynników korelacji pomiędzy rozwojem czerwiu zasklepionego poszczególnych kast pszczelich. Pozwoli to być może na zaniechanie czasochłonnego określania OCZ robotnic, a tym samym na wyhodowanie 5-6 pokoleń w ciągu roku. 13

8 W 1992 roku do hodowli użyto pszczół rasy kraińskiej, a od 1993 roku również mieszańce A. m. capensis x A. m. camica (Fj i dalsze pokolenia) krzyżowanych wypierająco trutniami kraińskimi. Okres trwania stadium zasklepionego matek określano metodą własną (W i l d e i S i u d a 1992). Moment zasklepiania komórek pszczelich określano posługując się metodą znakowania komórek na przykładanej do plastra folii. Przy określaniu OCZrobotnic posługiwano się metodą opracowaną przez L a n g e n b a c h (1991). Do określenia OCZ trutni posłużono się metodą własną (W i l d e i S i u d a 1992). Część matek pszczelich unasieniano nasieniem pobranym od jednego trutnia o znanym OCZ, pozostałe matki - jednorazowo dawką 8 mm! nasienia. Porniędzy matkami a ich synami stwierdzono umiarkowaną lecz wysoko istotną korelację (r=0.54 p<0,01) (tab.3). Współczynnik korelacji dla matek i matek-córek był niski (r=0,29), lecz bliski istotności (p <0,07). Współczynnik regresji matek-córek na matki wynosił b=0,78 a synów b=2,34. Współczynnik odziedziczalności OCZ dla matek-córek wynosił h 2 =0,6 a dla synów h 2 =0.45 (tab.3). Współczynniki korelacji oszacowane w 1992 roku wynosiły. pomiędzy robotnicami a ich matkami r=0.26 p<o.ol i r=-0.14 p<0.05 oraz ich ojcami r=0,28 p-cu.ol (tab.3). Współczynniki regresji wynosiły odpowiednio: b=0,33 i b=-0.14 oraz b=0.]2. Natomiast współczynnik odziedziczalności wynosił h 2 =0.66 i h 2 =0.37 pomiędzy matkami a robotnicami oraz h Z =0,24 pomiędzy ojcami i robotnicami. Współczynnik korelacji pomiędzy matkami a matkami-córkami pokolenia F6 mieszańców był wysoki (r= 0,73) oraz wysokoistotny statystycznie (p< 0.01), współczynnik regresji matek-córek na matki wynosił b=3,51, natomiast współczynnik odziedziczalności został przeszacowany h 2 > 1 (tab.3). Współczynnik korelacji pomiędzy robotnicami a ich matkami wynosił r=0,83 p<o,ol oraz ich ojcami r=0,28 p<o.01 (tab.3). Współczynniki regresji wynosiły odpowiednio: b= 1.03 oraz b=o.12. Współczynnik odziedziczalności pomiędzy matkami a robotnicami natomiast wynosi! h 2 > 1 oraz h 2 =0.63 pomiędzy ojcami j robotnicami (tab.3). W ]994 roku współczynnik korelacji wynosił r=-0,]4 i był statystycznie istotny (p<0,05), współczynnik regresji robotnic na matki wynosił b=-0.19 a współczynnik odziedziczalności h 2 =0.6. W 1993 roku pomiędzy matkami dla matek-córek i robotnic od strony matek przeszacowano współczynniki odziedziczalności. Przypuszczać należy. iż powodem była mała zmienność genetyczna oszacowana na 5,23%. W 1992 roku oraz 1994 współczynniki regresji oraz korelacji pomiędzy matkami unasienionymi 8 mm" nasienia jednolicie mieszanego a robotnicami. były ujemne. Świadczyć to może o dużym wpływie trutni na kształtowanie się OCZ u pszczół. Do podobnego wniosku doszli M o r i t Z i Jor d a n (1992). Jednak oszacowane w doświadczeniu współczynniki odziedziczalności były niższe niż uzyskane przez tych autorów (0,76). W naszym doświadczeniu współczynniki odziedziczalności były podobne jak u B li c h l e r a i D r e s c h e r a (1990) oraz L e C o n t e i in. (1994). Natomiast w 1993 i 1994 współczynnik ten osiągnął podobną wartość (0.6) jak u H a r b o (1992). W związku z uzyskaniem tak różnorodnych wyników w poszczególnych latach badań, wydaje się. iż na obecnym etapie prowadzonych prac nad uzyskaniem pszczół o krótkim OCZ możliwe jest ograniczone wykorzystanie tych współczynników w dalszej hodowli. W pracach selekcyjnych należy więc opierać się nadal na bardzo pracochłonnym określaniu OCZ każdego hodowanego pokolenia. Słowa kluczowe: hodowla, selekcja, odporność. Varroajacobsoni, okres czerwiu zasklepionego, korelacja, odziedziczalność. 14