Wong, K. C.

Universiti Putra Malaysia Institutional Repository

FOR Category F10900: Agricu~ural SciencesSTUDIES ON SELF-INCOMPATIBILITY SYSTEM OFDURIAN (DURIO ZEBITHENUS MURR)K.C. WongFaculty of AgricultureUniversiti PutTa Malcrvsia, 43400 UPM, Serdang, SelangOT,MalaysiaKeywords: 'durian, Durio zebithenus, self-incompatibility, distyly, pollination.IntroductionThe floral structure of durian' has' been described by Val-mayor et al. (1965), While m While durian flowers have beenshown to be self-incompatible (Valmayor et al. 1965; Shaari,et al. 1985; Zainal Abidin, 1990) there is also evidence to in-dicate that the flower can be self-compatible (Soepadma and ,Bow,J976). The self-incompatibility system has been statedto be that of heterostylous (Chin and Poon, 1982) probably,from the observation that variation in the length of styles andstamens occurred among the clones (Soepadmo and Bow"1976). This statement may not be strictly true. Previousstudies have been confined to a single clone or, at most, afew clones, thus comprehensive studies covering all availableclones in Malaysia, are lacking. The present study aims toshed some,light on the self-incompatibility system of durianso as to overcome,theabove controversy.Materials and MethodsExperiments were carried out during the durian floweringseasons of September 1996-February 1997; July-December1997; and September-December 1998. In a preliminary trial,the receptivity of the stigma was investigated by pollinatingat various time intervals before anthesis. The first trial con-sisted of 25 co'mbinations of self and cross pollinationswhich were carried out among durian clones of D2, D8, D24,D66, .andD84. Prior to pollination, emasculations of stamenswere carried out on the chosen flowers, which were thenbagged with muslin bags. On the next evening, commencingfrom 6.30 pm onwards, pollinations were carried out on theemasculated flowers. After pollinations, the flowers wereagain bagged to prevent from contamination. Fruit sets andfruit development was recorded periodically until maturity offruits. In addition to pollinations in the field, the compatibil-ity or incompatibility of the various selfings and crossingswere also studied using fluorescence microscopy, followingthe protocol described by Wong et al. 1994. The above trialwas repeated during the second and third flowering seasonsto monitor the repeatability of results.Results and Discussion'Durian flowers are normally fully open (anthesis)at 6.30 pmand natural, pollination takes place during the night. In thepreliminary trial to study the receptivity of the stigma,' it wasfound that bud,pollinations carried out at 6-10 h before an-thesis' resulted: in significantly higher, fruit sets, than thosepollinated' at 3-4h before or' at anthesis.' There were, how-'ever, clonal differences in the above responses. This findingis significant because it reveals that the operation of artificial'pollination can be carried out during the daytime. Similarfinding has been reported by Valmayor et al. (1965). In trials'where selfings and crossings of clones D2, D8, D24, D66and D84 were carried out in all combinations over the three,flowering seasons, it was found that there were clonal differ-ences in response to the various pollinations. Except for'clone D8, all other clones exhibited self-incompatibility.With clone D8, selfing had successfully produced maturedfruits, thus indicating that this clone is self-compatible. Re-sults with cross-pollinations revealed that there were varia-tions among clones with regard to cross compatibility. CloneD24 and D66 were cross compatible with all the clonestested in this study: However, D24 showed differential re-sults depending on whether it was used as gynoecia or pol-leniser. All other clones showed the same results irrespectiveof gynoecia or polleniser role. Among clones exhibitingcross-incompatibility, D2 showed incompatibility with D8and D24; D8 showed incompatibility with D2, D24, andD84; and D84 was incompatible with D8. These findings areuseful when selecting different clones planting under poly-clonal planting system. Studies' with fluorescence micros-copy confirmed the results of the above pollinations. A tech-nique has also been developed to section the large flower intovarious segments for staining .andmicroscopic work.ConclusionsHigher fruit sets were obtained when durian flowers werepollinated 6-10 h before anthesis. Majority of the durianclones investigated were self-incompatible. However, cloneD8 was found to,show self-compatibility.Clonal variations were shown by' the clones in cross com-,patibility.When used as gynaecial material, D24could setfruits when pollinated by pollens from D2, D8, D66 andD84. A protocol has been developed for studying pollen tubegrowth under fluorescence microscopy.ReferencesChin, H.F. and Poon, A.C.G. 1982. A scanning electron microscopestudy on flowers of carambola, durian and rambutan"Pertanikil.<, 5: 234-239. ' 'Shaari, A.R., Zainal, A.B., and Shamsudin, M. 1985. Some aspects,of pollination and fruit set in durian cultivar 024, Teknologi'BuahBuahan.'l:l-4. ' 'Soepadmo, E. and Eow, B.K. 1976. The reproductive biology 'ofDurio zibethinus, Gardens' Bull., Singapore. 29: 25-33.Valmayor, R.V., Coronel, R.E., and Ramirez, O.A. 1965. Studies onfloral biology, fruit set and fruit development in durian, ThePhillippine Agriculturist. 48: 355-366. ,:. 'Wong, K.C., Wetanabe.: M.and Hinata, K.'1994. Fluorescence andscanning electron microscopic study on self-incompatibility indistylous Averrhoa carambola L., Sex Plant Reprod. 7: 116-121.Zainal Abidin, M. 1990. Sistem penanarnan campuran klon bagi du-rian,Teknologi Buah Buahan. 6: 1-4.Supported by IRPA Grant Ol-02..fJ4-001955

Studies on self-incompatibility system of durian (Durio zebithenus Murr)

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Studies on self-incompatibility system of durian (Durio zebithenus Murr)

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