Maize (Zea mays L.) yield and aflatoxin accumulation responses to exogenous glycinebetaine application

Abstract Exogenously applied glycinebetaine (GB) accumulates at high levels in maize (Zea mays L.). Under water deficit and high temperature conditions GB application produces yield benefits. These sub-optimum conditions often result in high levels of aflatoxin accumulation which reduces grain quality. A 3-year (2008, 2009 and 2010) field experiment was conducted to determine the effects of GB on maize yield and aflatoxin accumulation. Weekly and alternate weekly GB application increased plant biomass by 10 and 13%, respectively. Net photosynthesis increased by 6% with GB application; however, stomatal conductance, transpiration rate and electron transport rate were not significantly affected. Grain yield increased by 6 and 13% with GB applied alternate weekly and weekly, respectively, over control plots averaged over years. GB application resulted in a trend of reduced aflatoxin accumulation in inoculated ears compared with non-inoculated controls in 2009 and 2010; however, inherent field and sampling variation did not allow us to conclude statistically any advantage attributable to GB application. We can conclude that GB did not significantly reduce aflatoxin production in the inoculated treatments

The genetics of divergence and reproductive isolation between ecotypes of Panicum hallii

The process of plant speciation often involves the evolution of divergent ecotypes in response to differences in soil water availability between habitats. While the same set of traits is frequently associated with xeric/mesic ecotype divergence, it is unknown whether those traits evolve independently or if they evolve in tandem as a result of genetic colocalization either by pleiotropy or genetic linkage. The self-fertilizing C4 grass species Panicum hallii includes two major ecotypes found in xeric (var. hallii) or mesic (var. filipes) habitats. We constructed the first linkage map for P. hallii by genotyping a reduced representation genomic library of an F2 population derived from an intercross of var. hallii and filipes. We then evaluated the genetic architecture of divergence between these ecotypes through quantitative trait locus (QTL) mapping. Overall, we mapped QTLs for nine morphological traits that are involved in the divergence between the ecotypes. QTLs for five key ecotype-differentiating traits all colocalized to the same region of linkage group five. Leaf physiological traits were less divergent between ecotypes, but we still mapped five physiological QTLs. We also discovered a two-locus Dobzhansky-Muller hybrid incompatibility. Our study suggests that ecotype-differentiating traits may evolve in tandem as a result of genetic colocalization