Managing flowering time inMiscanthusand sugarcane to facilitate intra- and intergeneric crosses
Authors: Dong Hongxu , Clark Lindsay V. , Jin Xiaoli , Anzoua Kossonou , Bagmet Larisa , Chebukin Pavel , Dzyubenko Elena , Dzyubenko Nicolay , Ghimire Bimal Kumar , Heo Kweon , Johnson Douglas A. , Nagano Hironori , Sabitov Andrey , Peng Junhua , Yamada Toshihiko , Yoo Ji Hye , Yu Chang Yeon , Zhao Hua , Long Stephen P. , Sacks Erik J. 
Published: September 2020

Miscanthusis a close relative ofSaccharumand a potentially valuable genetic resource for improving sugarcane. Differences in flowering time within and betweenMiscanthusandSaccharumhinders intra- and interspecific hybridizations. A series of greenhouse experiments were conducted over three years to determine how to synchronize flowering time ofSaccharumandMiscanthusgenotypes. We found that day length was an important factor influencing whenMiscanthusandSaccharumflowered. Sugarcane could be induced to flower in a central Illinois greenhouse using supplemental lighting to reduce the rate at which days shortened during the autumn and winter to 1 min d-1, which allowed us to synchronize the flowering of some sugarcane genotypes withMiscanthusgenotypes primarily from low latitudes. In a complementary growth chamber experiment, we evaluated 33Miscanthusgenotypes, including 28M. sinensis, 2M. floridulus, and 3M. ×giganteuscollected from 20.9° S to 44.9° N for response to three day lengths (10 h, 12.5 h, and 15 h). High latitude-adaptedM. sinensisflowered mainly under 15 h days, but unexpectedly, short days resulted in short, stocky plants that did not flower; in some cases, flag leaves developed under short days but heading did not occur. In contrast, forM. sinensisandM. floridulusfrom low latitudes, shorter day lengths typically resulted in earlier flowering, and for some low latitude genotypes, 15 h days resulted in no flowering. However, the highest ratio of reproductive shoots to total number of culms was typically observed for 12.5 h or 15 h days. Latitude of origin was significantly associated with culm length, and the shorter the days, the stronger the relationship. Nearly all entries achieved maximal culm length under the 15 h treatment, but the nearer to the equator an accession originated, the less of a difference in culm length between the short-day treatments and the 15 h day treatment. Under short days, short culms for high-latitude accessions was achieved by different physiological mechanisms forM. sinensisgenetic groups from the mainland in comparison to those from Japan; for mainland accessions, the mechanism was reduced internode length, whereas for Japanese accessions the phyllochron under short days was greater than under long days. Thus, forM. sinensis, short days typically hastened floral induction, consistent with the expectations for a facultative short-day plant. However, for high latitude accessions ofM. sinensis, days less than 12.5 h also signaled that plants should prepare for winter by producing many short culms with limited elongation and development; moreover, this response was also epistatic to flowering. Thus, to flowerM. sinensisthat originates from high latitudes synchronously with sugarcane, the former needs day lengths >12.5 h (perhaps as high as 15 h), whereas that the latter needs day lengths <12.5 h.