Environmental responsiveness of flowering time in cassava genotypes and associated transcriptome changes

Abstract

Cassava is an important food security crop in tropical regions of the world. Cassava improvement by breeding is limited by its delayed and poor production of flowers, such that cassava flowering under field conditions indirectly lengthens the breeding cycle. By studying genotype and environment interaction under two Nigerian field conditions (Ubiaja and Ibadan) and three controlled temperature conditions (22°C/18°C, 28/24°C and 34/30°C (day/night)), we found that while early flowering genotypes flowered at similar times and rates under all growing conditions (unfavorable and favorable field and controlled-temperature environments), late flowering genotypes were environmentally sensitive such that they were substantially delayed in unfavorable environments. On the basis of nodes-to-flower, flowering of late genotypes approached the flowering time of early flowering genotypes under relatively cool Ubiaja field conditions and in growth chambers at 22°C, whereas warmer temperatures elicited a delaying effect. Analysis of transcriptomes from leaves of field and controlled-temperature environments revealed that conditions which promote early flowering in cassava have low expression of the flowering repressor gene TEMPRANILLO 1 (TEM1), before and after flowering. Expression data of field plants showed that the balance between flower stimulatory and inhibitory signaling appeared to correlate with flowering time across the environments and genotypes.

Flower-inducing technology facilitates speed breeding in cassava

“…Temperatures at Palmira compared to lowland tropics, respectively, have an average maximum of 30.1 ± 2.7 vs. 33 ± 1°C, and a minimum of 19.2 ± 1.2 vs. 23 ± 0.5°C. Studies of cassava under controlled-environment conditions of growth chambers have indicated that photoperiod and temperature interact such that the strongest flower induction is with long-day photoperiods and cool temperatures flowering ( Adeyemo et al., 2019 ; Oluwasanya et al., 2021a ; Oluwasanya et al., 2021b ; Hyde and Setter, 2022 ). High temperatures negate the benefit of extended photoperiod ( Hyde and Setter, 2022 ).…”

Development of Methods for Improving Flowering and Seed Set of Diverse Germplasm in Cassava Breeding

“…Such genotypes are good candidates for PGR and pruning methods because they are late flowering and usually do not generate many seeds in crossing nurseries. Furthermore, there are environmental effects on flower timing and development [14,17,21,35], and different locations might have different optimal treatment strategies. The present investigation developed a protocol that adjusts the dosage and timing of treatments to accommodate differences in growth, time of flowering and sensitivity to the growth regulators so that flower and seed production are enhanced among a wide range of environments and genotypes and cassava breeding programs can successfully use a diversity of germplasm to develop cultivars with needed traits.…”

“…Recently, progress has been made to identify factors that affect floral initiation and development in cassava. Cooler temperatures and longer photoperiods interact with the FT flowering regulatory system to influence the transition of the apical meristem to an inflorescence [14,16,17,20,21]. Floral development after initiation is affected by two plant hormones in cassava: ethylene and cytokinins.…”

Q&A: Methods for estimating genetic gain in sub‐Saharan Africa and achieving improved gains

“…RGA refers to a set of techniques that involve manipulating the environmental conditions in which crop genotypes are grown (Wanga et al, 2021). Rodrmguez et al (2023) used 150 cassava progenitors to evaluate the effectiveness of flower-inducing technology, including photoperiod extension , pruning (Pineda, Yu, et al, 2020), and plant growth regulators (Oluwasanya et al, 2021). The authors found that time to flowering significantly decreased for all progenitors under extended lighting regimes.…”