Differential Growth and Transpiration Responses Among Banana (Musa Spp.) Hybrids—Hope for Breeding Drought Tolerant Bananas?

Abstract

Drought stress greatly impacts banana (Musa spp.) production (Van Asten et al. 2011), limiting its growth and yield. In the East African Great Lakes region, East African highland bananas (EAHBs) dominate the agricultural production systems (Karamura et al. 2012). They are considered endemic to the region with no clear analogues elsewhere in the world. The existing EAHB genetic diversity is limited, as it is only based on somaclonal mutations and continuous farmer selection (Perrier et al. 2011). The polygenic nature of drought tolerance, coupled with banana's inherent sterility and polyploid nature, is a challenge to the crop's improvement through crossbreeding, but several hybrids with improved pest and disease traits and higher yield have been made (Batte et al. 2019). EAHBs are mainly grown on smallholder farms where they provide food and income security. They only occur at high altitudes (900–2000 m above sea level), which are associated with cooler temperatures and hence a lower evaporative demand (Karamura et al. 2012). Their high‐water usage, low water use efficiency, and weak drought avoidance mechanism make them vulnerable to higher evaporative demands (Eyland et al. 2021). Considering this water‐spending nature, global warming and market preferences (Akankwasa et al. 2020), it is crucial to improve the resilience of these endemic banana varieties to future environmental conditions through breeding. The objectives of the study were to determine the impact of meiotic recombinations on the variability of water usage and assess the growth behaviour and transpiration responses of secondary banana hybrids and their parental lines to declining soil water content (SWC) in function of light intensity (photosynthetic active radiation, PAR) and vapour pressure deficit (VPD). We hypothesised that despite the narrow genetic diversity observed within the EAHB varieties and the high‐water usage, the meiotic recombination would lead to the segregation of reactions of transpiration responses and resulting growth to fluctuating VPD, PAR and SWC. To our knowledge, we present the first study that evaluates the performance of bananas developed purposely for improved drought avoidance and tolerance majorly based on the ‘Musa acuminata’ genetic background. Materials and methods can be found in Supporting Information S2. Two phenotyping experiments were performed concurrently at the Bioversity International phenotyping facility (Phenospex, Heerlen, Netherlands) hosted at KU Leuven, in Leuven, Belgium. Eighteen banana genotypes comprising 16 EAHB progenies and their two parental lines, ‘917K‐2’ (female) and ‘TMB2x9172’ (male), were phenotyped (Supporting Information S3: Table S1). Plant growth and transpiration were monitored as a function of the environment (SWC, PAR and VPD). To disentangle the environmental impacts, transpiration rates were additionally modelled according to the Jarvis–Stewart model (Jarvis 1976; Eyland et al. 2022).