Biology Reference
In-Depth Information
Chapter 8
Molecular Breeding forStay-Green:Progress
and Challenges inSorghum
VincentVadez,SantoshDeshpande,JanaKholova,PunnaRamu,and C.TomHash
Abstract
The stay-green trait is regarded as the best characterized characteristic conferring drought adaptation
in several crops including sorghum. Quantitative trait loci (QTLs) for stay-green have been identified
using several bi-parental populations. Several of these QTLs are currently being used for introgression
in a number of genetic backgrounds. Part of the challenge in the introgression of these QTLs lays in
the limited polymorphism between donor and recurrent parents. As a consequence, certain QTL can't
always be distinguished, such as Stg3 and StgB which are on the same chromosome, SBI-02. Current
progress in marker technology is contributing to enhancing the marker coverage of QTL intervals
and this would improve breeding efficiency. Despite the knowledge of genomic regions conferring
the stay-green trait, it is surprising that knowledge of the physiological mechanisms explaining stay-
green are still relatively unknown. Early explanations focused on a role of stay-green as maintaining
photosynthetic activity. It has also been hypothesized that the stay-green trait relates to the plant
nitrogen balance and in particular to the capacity to absorb nitrogen during the post-anthesis period. It
is only relatively recently that water availability during the post-anthesis period, that is, when the stay-
green phenotype expresses itself, has been proposed as a possible cause for the stay-green phenotype.
However, the reasons that water is left for absorption are still unexplained and could be accounted
for by either a deeper soil extraction depth or water saving traits operating at early stages. As the
mechanisms responsible for stay-green become more evident and as DNA-sequencing technologies
offer denser genome coverage, the likelihood is that the future of manipulating the stay-green trait
will be about manipulating its physiological components.
phenotype, SG) is an intriguing crop feature that
has long been studied and included in breed-
ing programs in several crops, especially under
water-limited conditions. Indeed, the mainte-
nance of green leaf area has been reported
Introduction
The capacity of certain genotypes in several
annual crop species to maintain green leaves
during the grain-filling period (the “stay-green”
Search WWH ::
Custom Search