Variability in the root system of East African banana genotypes

Abstract

The banana (Musa spp.) root system is important for plant anchorage and the uptake of nutrients and water and thus, strongly influences plant growth and subsequent yields. Previous research studies on the Musa spp. root system have predominantly focused on high value export dessert bananas (AAA group) and plantains (AAB group). The study reported in this paper compared root system development of East African highland bananas (AAA-EA group) with other Musa groups. Two separate studies were conducted. One of the studies focused on variability in root system development of 25 Musa genotypes, including 10 East African highland bananas, while the other experiment assessed variability in root distribution for 'Kibuzi' (AAA-EA, cooking banana), 'Gonja' (AAB, plantain) and 'Sukali Ndiizi' (AAB, dessert banana). Plants in the first study were completely excavated at 20 weeks after planting (WAP), while a sub-set of 5 East African highland bananas was also assessed at flower emergence. A 90 degrees section of the root system was assessed for pre-flowering plants in the second trial. Significant positive correlations were found between shoot and root traits for the plants assessed at 20 WAP and at flower emergence. In addition, there was no significant genotypic effect on the shoot root ratio indicating that all genotypes had a similar partitioning of dry matter between the shoot and the root system. In contrast, at 20 WAP significant genotypic effects were observed on individual shoot and root traits. Soil depth and genotype significantly (P<0.001) affected root dry weight and cord root length of the pre-flowering plants. The largest root system was observed for the AAA-EA 'Kibuzi', which also exhibited the most vigorous shoot and sucker (i.e., lateral shoot) growth again suggesting a strong shoot root relationship. Most roots were found in the upper 45 cm soil layer for all 3 genotypes. Horizontal distance from the plant x genotype had no significant effect on the root traits, indicating that all 3 genotypes had an evenly distributed root system up to 90 cm from the plant base.