Banana is an important food crop in Uganda. Its production per unit land area has declined doe to pests and diseases andsoil fertility depletion. Host plant resistance is a recommended intervention. However, banana breeding is technicallydifficult because oflow female fertilitv. The landraces in the field gene bank at Kawanda were pollinated with pollenfrom the wild banana 'Calcutta 4' to e~aluate them for seed fertility. Out ofthe 62 clones screened, 33 were seed-fertile.The most fertile land races belonged to 'Nakabululu' and 'Nfuuka' clone sets. Viable seeds were obtained from severalland races indicating that genetic improvement ofthese highland bananas through cross breeding is possible. Thefertile Iandraces should be cross-pollinated with improved diploids to produce resistant hybrids

Hartman, J

Karamura, E

Magambo, S

Makumbi, D

Namanya, P

Nuwagaba, L

Rubaihayo, P

Ssebuliba, R

Talengera, D

Vuylsteke, D

English

Uganda Journal of Agricultural Science (UJAS)

Uganda Journal of Agricultural Sciences, 2000, 5:36-38 Printed in Uganda. All rights reserved ISSN I 026-0919 ©2000 National Agricultural Research Organisation Towards improving highland ban.anas lSsebuliba R., zvuylsteke D., 2Hartman J., 1Mt1kumhi D., 2Tafengera D., 1Ruhailtayo P./Magambo S., 'Nuwagaha L., 1 Namanya P. tmd~ Karamura H. 1National Banana Research Program Kawanda Agricultural Research Institute P. 0. Box 7065, Kampala. 2)nlemationallnslitutc of Tropical Agriculture-Eastern and Sou them Africa Regional Cc:nler P. 0 . Box 7818, Kampala. 3 Dept. of Crop ScienceMakcrere University P. 0. Box 7062, Kampala. •tntemational Network for the Improvement of Banana and Plantain·Ea':>lern and Southern Africa P. 0. Box 24384, Kampala. Abstract Banana is an important food crop in Uganda. Its production per unit land area has declined doe to pests and diseases and soil fertility depletion. Host plant resistance is a recommended intervention. However, banana breeding is technically difficult because oflow female fertilitv. The landraces in the field gene bank at Kawanda were pollinated with pollen from the wild banana 'Calcutta 4' to e~aluate them for seed fertility. Out ofthe 62 clones screened, 33 were seed-fertile. The most fertile land races belonged to 'Nakabululu' and 'Nfuuka' clone sets. Viable seeds were obtained from several land races indicating that genetic improvement ofthese highland bananas through cross breeding is possible. The fertile Iandraces should be cross-pollinated with improved diploids to produce resistant hybrids. Key words: Production decline, seed fertility, resistant hybrids, female fet1ility. Introduction Banana (Musa spp.) is an important food crop in Uganda. Annual production is estimated at 8.44 million tons accounting for 15 % of total world production output (Karamura, 1993). More than 85% of the banana_~ grown in Uganda are East African highland banana (EAHB) landraces (Musa spp., AAA group, ' matooke' and 'mbidde') (Karamura et ai., 1996). The crop is grown on 1.5 million hectares equivalent to 38% of land under crops and is a staple for 7 million people. It is also an impotiant source of income and has a high industrial potential through juice, wine and assorted post-harvest food stuffs. During the past twenty years, banana production per unit land area has steadily declined due to increasing pest and disease pressure (Gold et a/., 1993 ). Banana weevil and a complex of parasitic nematodes are the major pests, while fungal leaf spots (mainly black sigatoka) and viruses are the most important diseases. Decline in soil fertility also contributes to decreasing yields (Zake et al., 1994, Bwamiki and Ssal~ 1998). Breeding for host plant resistance is an economically sustainable intervention (Stover and Simmonds, 1991 ). Successful cross breeding requires the production of true seed through sexual hybridization. However, the majority of the edible Mus a spp. are female~ sterile and, therefore, do not set seed on pollination (Shepherd eta/., 1987). There are more than 80 distinct clones (landraces) of highland bananas in Uganda, belonging to 5 clone sets (Karamura. 1998) and it was not known which of these were female-fertile. The objective of this research therefore was to identify female-fertile EA Hll that can be used in a cross breeding program. Materials and methods Plant material The EAHB landraces maintained in the field gene bank at Kawanda Agricultural Research Institute were screened for female fertili ty. Sixty-t\vo clones representing the major variability of the landraces grown in Uganda were selected, belonging to different clone sets; namely 'Musakala', 'Nfuuka', 'Nakitembe' , 'Nakabululu' and 'Mbidde' (Karamura, 1998). A total of J 0, 29, 6, 7 and I 0 clones w·ere pollinated for ' Musakala ' , 'Nfuuka ' , ' Nak itcmbe ', 'Nakabululu' and' Mbidde', respectively. These landraces were pollinated with pollen from 'Calcutta 4', a highly male-fertile wild diploid banana (Simmonds, 1953). Pollination Pollen from ' Calcutta4' was always collected around 7.00 a.m from male flowers at an thesis. Male buds were covered with cotton bags to prevent pollen contamination from other sources.1Likewisc, emerging inflorescences or the landraces were bagged with transparent plastic bags, to avoid potential natural crossing with alien pollen, until the last flower was pollinated. Hand pollinations were perfom1ed daily between 7.00 a.m and I 0.00 a.m (Shepherd, 1954) in freshly exposed tenm!c I .. 37 1Sscbuliba R., et al. flowers of the landraces by rubbing a cluster of male flowers (from 'Calcutta 4 ') on to the female flowe.rs. At full maturity, pollinated bunches were harvested and placed in a ripen ing t'oom. Seeds were extracted subsequently from fruits with yeJiow peel. Seed germination Embryos were extracted from seeds and germinated in vitro (Talengera et al., 1996). Data recorded Data wery recorded for number of bunches pollinated, number of bunches with seeds, total number of seeds, number of embryos obtained, and number of embryos germinated. Seed set per bunch was computed a~ the total number of bunches pollinated, divided by the total seeds obtained. Pollination success was computed as number of bunches with seed, divided by total number of bunches pollinated, multiplied by 100. Likewise, embryo success was computed as number of embryos germinated, divided by total number of embryos obtained, multiplied by I 00. Resuhs and discussion Seed set rates in the different clone sets ofEAHB Out of the 62 clones screened, 33 were seed-fertile (Table I). More than 80% and 70% of the clones in 'Nfuuka' and 'Nakabululu' clone sets, respectively, were seed-fertile, while only 10% and 30% of 'Musakala' and ' Mbidde', respectively, were fe11ile; none of the clones in ' Nakitembe' was female-fertile. Pollination success for 'Nakabululu' and 'Nfuuka' was about 60% and 48%, respective ly, and either very low or zero for the other clone sets. Similarly, seed set per bunch for 'Nakabululu' and 'Nfuuka' was 6.1 and 5.8, respectively, but either very low or zero for the other clone sets. Table 1. Seed set by clone set of East African highland bananas (December 1994- November 1997) Clone Number No. of seed Pollination Seed set set of clones fertile clones success (%) bunch·' Musakala 10 1 1.5 0.2b Nfuuka 29 24 47.9 5.8• Nakitembe 6 0 0.0 O.Ob Nakabululu 7 5 60.9 6.1" Mbidde 10 3 4.0 0.1b Means followed by the same letter are not significantly different according to the Lsmeans method of separating means. Table 2. Seed set in the ten most fertile landraces (December 1994- November 1997) Pollination Seed set Seeds with Embryo Clone success (%) bunch·' embryos (%) success (%) Entukura 93.9 25.6 52.1 3.2 Enzirabahima 85.4 19.0 55.2 2.7 Nante 50.0 14.0 63.5 7.8 Kabucuragye 75.8 12.5 44.3 6.5 Kazirakwe 69.2 10.6 42.0 0.0 Tereza 61.0 Nakasabira 83.3 Nakayonga 96.6 Nakitengwa 76.9 Enyeru 50.0 Seed set rales in t he different clones ofEAHB Seed set rates varied greatly among clones, even within the same clone set, with means ranging trom 0 to more than 25 seeds per bunch, and pollination succe~s of up to 90% in some clones (Table 2). Within the 'Nfuuka' clone set, the most seed-fertile landraces are ' Entukura', '£nzirabahima', ' Nante', 'Kabucuragye', 'Tereza' , 'Enyeru' and ' Nakitengwa', while in the ' Nakabululu ' clone set, 9.3 31.5 0.0 8.1 47.0 1.6 7.6 42.1 1.7 7.2 39.0 0.0 7.2 34.3 1.7 ' Kazirakwe ', 'Nakasabira', and 'Nakayonga' are the most fertile. The results of this study indicated that 33 out of62 clones were female-fertile, most of them belonging to the 'Nakabululu' and 'Nfuuka' clone sets (Table 1). Likewise, Vuylsteke et al. (1997) screened Ill plantain landraces belonging to French, French Horn, False Hom and True Horn types and identified 28 and 8 female-fertile cultivars be longing to the French and False Hom, respectively. This 38 Towards improving highland bananas stresses the importance of screening for female fertility in any Musa breeding program. There was also great variation in seed set within the same clone, e.g., seed set range in individual bunches of 'Entukura' was 0 to 227. Similar variations were made in plantains (Vuylsteke et a/., 1993) and in 'Gros Michel' (Simmonds, 1966 ). Studies by Ortiz and Vuy lsteke ( 199 5) revealed that seasonal changes accounted for the large fluctuation in seed set within the same cultivar. Thus, climatic factors might be the cause of the great variation observed in seed set within the same clone in this study. Seed germination Clones Nante, Enzirabahima and Entukura had more than 50% of their 'seeds' containing embryos, while Nakasabira, Kabucuragye, Nakayonga and Kazirakwe had embryos in at least 40% of their seeds. N ante had the highest embryo success (7 .8% ), followed by Kabucuragye (6. 5%), Entukura (3.2%) and Enzirabahima (2. 7%}. Although seed germination is a general problem in banana breeding (Vuylsteke et al., 1990; Bakry and Horry, 1992), viable seeds were obtained from several land races in the present study (Table2). Conclusion Genetic improvement of the highland bananas through cross breeding is possible, because viable seeds were obtained from severallandraces. Recommendation The female-fertile highland bananas identified in this study should be cross pollinated with improved diploid bananas (Rowe, 1984, 1990; Vuylsteke et al., 1997) to develop EAHB hybrids that express disease/pest resistance, with acceptable quality and improved agronomic traits. Acknowledgments This research was carried out with the financial support from the International Institute of Tropical Agriculture. The assistance obtained from the National Banana Research Program, Kawanda is highly appreciated. References Bakry, F. and Horry, P.J. 1992. Tetraploid hybrids from interploid 3X/2X crosses in cooking bananas. Fruits 47:641-647. Bwamiki, P .D. and Ssali, H. 1998. Banana-Crop resource management. In: Esele, J.P. (Ed.) Agriculture in Uganda. In press. Gold, C.S., Ogenga-Latigo, M.W. Tushemereirwe, W.K. Kashaija and Nankinga, C. 1993. Farmer perceptions of banana pest constraints in Uganda: Results of a rapid rural appraisal. In C.S. Gold and B. Gem mil (editors), Proceedings of a Research Coordination Meeting for Biological and Integrated Control of Highland Banana . and Plantain Pests and Diseases. liT A, Cotonou, Benin, PP3-24. Karamura, E.B. 1993 . The strategic importance of bananas/ plantains in Uganda. In C.S. Gold and B. Gemmil (editors), Proceedings of a Research Coordination Meeting for Biological and Integrated Control of High land Banana and Plantain Pests and Diseases. liT A, Cotonou, Benin, PP343-347. Karamura D. I 998. Numerical taxonomical studies of the East African highland bananas{Musa AAA-EastAfrica) in Uganda. Ph . D. Thesis. The University. of Reading, UK Karamura, DA., E. B. Karamuraand Gold, C.S. 1996. Cultivar distribution in primary banana growing regions of Uganda . .MUS'AFRICA, 9: 3-5. Ortiz, R. and Vuylsteke, D. 1995. Factors influencing seed set in triploid Musa spp. L. and production of euploid hybrids . Annals ofBotany 7 5: 151- 155. Rowe, P.R. 1984. Breeding bananas and plantains. Plant breeding Rev., 2, 135-155. Rowe, P.R. 1990. New genetic combinations in breeding bananas and plantains resistant to diseases in Musa. fn Jarret, R.L., ed. Identification of Genetic Diversity in the Genus Musa, ppl l4-123. INJBAP, Montpellier, France. Shepherd, K. 1954. Seed fertility of the Gros Michel banana in Jamaica. J. Hort Sci. 29(l ); 1-1 1. Shepherd, K., J. Dantas and Alves, E. 1987. Banana breeding in Brazil. In Persley, G. andDeLanghe, E. (eds.). Banana and plantain breeding strategies, pp. 78-83, ACIAR Proceedings No. 2 1. ACIAR, Canberra. Simmonds, N.W. 1953 . Segregation in some diploid bananas. J. Gent. 51: 458-469. Simmonds, N.W. 1966. Bananas. Tropical Agriculture Series. 2nd Edition. Longman. London and New York. 512p. Stover, R. and Simmonds, N. W. 1991 . Bananas. Tropical Agriculture Series. 3rd Edition. Longman. John Wiley and Sons. New York. 468p. Talengera, D., D. Vuylsteke and Kararnura, E. 1996. In vitro embryo germination of Uganda banana hybrids. MUSAFRlCA. Plantain and Banana Newsletter, No. 10. Page 14. International Institute ofTropical Agriculture. Vuylsteke, D., R. Swennen and De Langhe, E. 1990. Tissue culture technology for the improvement of African plantains. In Fullerton , R.A. and Stover, R H., eds. Sigatoka Leaf Spot Diseases ofBananas, pp316-337. INIBAP, Montpellier, France. Vuylsteke, D., Swennen R. and Ortiz, R. 1993. Development and performance of black sigatoka-resistant tetraploid hybrids of plantain (Mus a spp., AAB group). Euphytica 65:33-42. Vuylsteke, D., R. Ortiz, S. Ferris and Crouch, J. 1997. Plantain improvement. Plant Breeding Reviews. 14:267-320. Zake, J.Y.K., C. Nkwine, M. Okwakol, S. Sessanga, D.P. Bwamiki, J.K.Tumuhailwe, C. Na.ijuma and Kagole, H. 1994. Identification of suitable so ils and soil management practices for banana productivity. In: Rubaihayo P.R. (Editor). Banana-Based Cropping Systems Research Report. Department of Crop Science. Makerere University. ; 

Towards improving highland bananas

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Towards improving highland bananas

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