Environmental factors influence the production of flowers and fruits of cassava

Abstract

Cassava (Manihot esculenta Crantz) is a widely adaptable crop and plays a vital role in food security in many countries. Although farmers constantly demand improvements in crop productivity through genetic improvement, low flowering in the species can make it challenging to include some parents in crossing blocks or generate large populations. This study aimed to evaluate the influence of various environmental factors on cassava flowering by planting at different times of the year in the Recôncavo of Bahia region (Brazil). Thirty-five cassava accessions with contrasting flowering characteristics were planted in six different planting seasons, with a two-to-three-month difference between each planting date. Climate and flowering data were collected every two weeks during the experimental period, evaluating traits such as the number of days to the beginning of the first ramification (ND1B), flowering score (FS), score weighted by early flowering (SW) and height of the first branch (H1B). We found significant differences in all evaluated traits between planting seasons. The broad-sense heritability (ha2) and Cullis' heritability (hc2) were of medium (0.38 for FS) to high magnitude (0.98 for SW. Notably, the third planting season (February 2021), resulted in early flowering, approximately two months after planting, with SW of 10.40 and a higher flowering score of 0.56, representing a 52 % and 60 % increase compared to the first planting season, respectively. Our findings indicate that temperature and accumulated degree days are environmental factors correlated with increased flowering in cassava. Moreover, the dispersion of the genotypes in the two principal component analysis showed differences across the six planting seasons, indicating the environmental influence on the expression of flowering in this species. These findings can help breeders make reliable decisions when setting up crossing fields to accelerate the acquisition of improved progenies.