Abstract
BackgroundKernel moisture at harvest is an important trait since a low value is required to prevent unexpected early germination and ensure seed preservation. It is also well known that early germination occurs in viviparous mutants, which are impaired in abscisic acid (ABA) biosynthesis. To provide some insight into the genetic determinism of kernel desiccation in maize, quantitative trait loci (QTLs) were detected for traits related to kernel moisture and ABA content in both embryo and endosperm during kernel desiccation. In parallel, the expression and mapping of genes involved in kernel desiccation and ABA biosynthesis, were examined to detect candidate genes.ResultsThe use of an intermated recombinant inbred line population allowed for precise QTL mapping. For 29 traits examined in an unreplicated time course trial of days after pollination, a total of 78 QTLs were detected, 43 being related to kernel desiccation, 15 to kernel weight and 20 to ABA content. Multi QTL models explained 35 to 50% of the phenotypic variation for traits related to water status, indicating a large genetic control amenable to breeding. Ten of the 20 loci controlling ABA content colocated with previously detected QTLs controlling water status and ABA content in water stressed leaves. Mapping of candidate genes associated with kernel desiccation and ABA biosynthesis revealed several colocations between genes with putative functions and QTLs. Parallel investigation via RT-PCR experiments showed that the expression patterns of the ABA-responsive Rab17 and Rab28 genes as well as the late embryogenesis abundant Emb5 and aquaporin genes were related to desiccation rate and parental allele effect. Database searches led to the identification and mapping of two zeaxanthin epoxidase (ZEP) and five novel 9-cis-epoxycarotenoid dioxygenase (NCED) related genes, both gene families being involved in ABA biosynthesis. The expression of these genes appeared independent in the embryo and endosperm and not correlated with ABA content in either tissue.ConclusionsA high resolution QTL map for kernel desiccation and ABA content in embryo and endosperm showed several precise colocations between desiccation and ABA traits. Five new members of the maize NCED gene family and another maize ZEP gene were identified and mapped. Among all the identified candidates, aquaporins and members of the Responsive to ABA gene family appeared better candidates than NCEDs and ZEPs.
Highlights
Kernel moisture at harvest is an important trait since a low value is required to prevent unexpected early germination and ensure seed preservation
This study showed that kernel drying in field condition is genetically controlled
QTLs for kernel water status were frequently associated with QTLs for abscisic acid (ABA) content in embryo and/or endosperm, providing tools for marker assisted selection
Summary
Kernel moisture at harvest is an important trait since a low value is required to prevent unexpected early germination and ensure seed preservation. Maize (Zea mays) kernel moisture at harvest is an important trait in temperate regions because costly additional drying is needed to reach 15% water content, which is the level compatible with good seed preservation during storage. The late embryogenesis abundant (LEA) proteins including the dehydrin family, are produced during the maturation phase [8]. They have been assumed for a long time to protect cellular and molecular structures from the damaging effect of desiccation [8], only recent results shed some light on their precise action. Because members of the PIP2 and TIP1 families have much higher water transport capacities than those of the PIP1 family [12], aquaporins of the first two families may be of higher significance for desiccation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
