Effect of an Introgressed Nicotiana tomentosa Leaf Number QTL on Yield and Quality Characteristics in Flue‐Cured Tobacco

Abstract

Increased cured leaf yield is an important breeding target for flue‐cured tobacco (Nicotiana tabacum L.), but genetic improvement for this trait has slowed in the last thirty years. Yield is positively correlated with days to flowering and leaf number in this species. Use of novel allelic diversity influencing these traits might contribute to further yield improvement. In this study, an introgressed quantitative trait locus (QTL) affecting flowering time and leaf number, designated as Many Leaves (Ml), was backcrossed into three genetic backgrounds of flue‐cured tobacco. Field evaluation of nearly isogenic MlMl lines and Mlml hybrids indicated that the QTL acted in an additive to partially dominant fashion to delay flowering and increase leaf number. This resulted in significant increases in yield and cash return per hectare. As the zygosity of Ml increased, corresponding decreases in percentage total alkaloids and increases in percentage reducing sugars were observed, however. Incorporation of Ml into flue‐cured tobacco breeding programs may be useful for increasing cured leaf yields in certain environments. Concurrent modification of the genetic potential to accumulate alkaloids would be also important under current industry requirements, however.

Heat Unit Accumulation and Days to Anthesis Relationship in Tobacco Genotypes with an Introgressed QTL Affecting Leaf Number

“…The development of the MlMl and Mlml nearly isogenic versions (BC 6 stage of backcrossing) of flue‐cured tobacco genotypes Speight 168, K326, and NCTG‐61 were previously described (Eickholt and Lewis, 2014). Homozygous ( MlMl ), heterozygous ( Mlml ), and null segregant ( mlml ) versions of the three important flue‐cured tobacco genotypes, along with the recurrent parental lines per se were evaluated in replicated field experiments during 2011 and 2012 (Table 1).…”

“…Homozygous ( MlMl ), heterozygous ( Mlml ), and null segregant ( mlml ) versions of the three important flue‐cured tobacco genotypes, along with the recurrent parental lines per se were evaluated in replicated field experiments during 2011 and 2012 (Table 1). Field production practices for these experiments were previously described (Eickholt and Lewis, 2014), and data for days to flower and leaf number were extracted from the dataset of that project.…”

“…This study was performed to determine the relationship in the field between heat unit (HU) accumulation and the onset of anthesis in tobacco genotypes varying for the zygosity of an introgressed quantitative trait loci (QTL) designated as Many Leaves (Ml) affecting flowering team and leaf number. The goal of Eickholt and Lewis (2014) was "to determine if the many leaf trait (Ml) might be used to increase yields without adversely affecting leaf quality and chemistry across several flue-cured genetic backgrounds." In each environment, the MlMl, Mlml, and mlml genotypes were found to be grouped according to the zygosity of the Ml trait, with the mlml genotypes flowering first followed by Mlml and MlMl genotypes, respectively.…”

“…It is not known whether the plant‐bed transplant production system had a promoting effect on the earlier flowering. In a more recent study, Eickholt and Lewis (2014) studied genotypes with an introgressed QTL designated as Many Leaves ( Ml ), and found the QTL to act in a partially additive to dominant fashion to cause a delay in flowering time, along with increases in leaf number, plant height, and green leaf yield. The goal of Eickholt and Lewis (2014) was “to determine if the many leaf trait ( Ml ) might be used to increase yields without adversely affecting leaf quality and chemistry across several flue‐cured genetic backgrounds.” These authors established homozygous ( MlMl ) and heterozygous ( Mlml ) nearly isogenic versions of three important flue‐cured tobacco lines (Speight 168, K326, and NCTG‐61).…”

Adding genome‐wide genotypic information to a tobacco (Nicotiana tabacum) breeding programme

“…For tobacco, there are some studies associating markers with genes controlling quantitative traits such as disease resistance and yield components (Eickholt & Lewis, 2014; Vontimitta & Lewis, 2012). In addition, reference genomes for this species have become publicly available (Edwards et al, 2017; Sierro et al, 2014).…”