In vitro propagation of two banana cultivars

Bananas are one of the most important and profitable crops in Ethiopia. The energy and nutritional status of bananas are much higher than other common tropical and subtropical fruits. Over the past few years, production has considerably dropped in Ethiopia: yields per hectare currently vary between 5 and 9 tons, while the global average is 16 tons/ha.

This drop in production is due to insects, diseases and viruses attacking the crops as well as to the lack of improved varieties and healthy material. Micropropagation for rapid mass multiplication was used to tackle the second issue, however its application on a commercial scale is limited because of the high ratio of plant decline caused by the weak rooting capacity after transplants.

Researchers from Dilla University (Ethiopia) tried to establish an in vitro growth protocol for the Poyo and Grand Naine varieties starting from shoots. In order to induce rooting, shoots were cultivated on a solid substrate containing 30 g/L sucrose, 6 g/L agar and vitamins. Rooting occurred by adding various hormone concentrations to the substrate (PGR, plant growth regulator): IBA and NAA (0.5, 1.0, 1.5, 2.0 mg/L), applied either singularly or combined (0.5 mg/L IBA + 0.5 mg/L NAA and 1.0 mg/L IBA + 1.0 mg/L NAA). PGR-free medium was used as control. 

Rooted plants were then acclimatised under greenhouse conditions and transplanted in vases with clayey, sandy, compost and mixed (2 (clay): 1 (sand): 1 (compost) ratio) soil and finally transferred to the fields, where survival was assessed after 4 weeks. Results showed that hormones are needed for rooting, regardless of whether NAA and IBA are used singularly or combined. Poyo shoots responded well to IBA 0.5 mg/L concentrations, generating a better root system in terms of number and length of single roots.

A shorter rooting time was obtained applying 2-0 mg/L of NAA for both varieties. As for the Grand Naine variety, an IBA concentration of 1.5 and 0.5 mg/L had positive effects on the number of roots developed and maximum length respectively. The combination of 1.0 + 1.0 mg/L of IBA and NAA accelerated rooting, while it had no promising effects on Poyo.

A comparison of the performances of both varieties showed that Poyo is far superior than Grand Naine except for survival rate in fields, suggesting that the difference is due to the response to PGRs. However, the higher percentage of the survival ratio (70-90%) was reached when plants were cultivated using the 2 mg/L IBA and NAA concentrations applied singularly.

Source: Mulugeta Gobena, Sunil T. Hajare, Girmaye Benti, 'In vitro Root Development System in Two Popular Cultivars of Banana', International Journal of Current Microbiology and Applied Sciences, Vol. 7(1), pag. 3583-3591. 

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