Pre-harvest Sprouting and Grain Dormancy in Sorghum bicolor: What Have We Learned?

Abstract

The possibility of obtaining sorghum grains with quality to match the standards for a diversity of end-uses is frequently hampered by the susceptibility to pre-harvest sprouting (PHS) displayed by many elite genotypes. For these reasons, obtaining resistance to PHS is considered in sorghum breeding programs, particularly when the crop is expected to approach harvest maturity under rainy or damp conditions prevalence. As in other cereals, the primary cause for sprouting susceptibility is a low dormancy prior to crop harvest; in consequence, most research has focused in understanding the mechanisms through which the duration of dormancy is differentially controlled in genotypes with contrasting sprouting behavior. With this aim two tannin-less, red-grained inbred lines were used as a model system: IS9530 (sprouting resistant) and Redland B2 (sprouting susceptible). Redland B2 grains are able to germinate well before reaching physiological maturity (PM) while IS9530 ones can start to germinate at 40–45 days after pollination, well after PM. Results show that the anticipated dormancy loss displayed by Redland B2 grains is related reduced embryo sensitivity to abscisic acid (ABA) and increased levels of GA upon imbibition. In turn, transcriptional data showed that ABA signal transduction is impaired in Redland B2, which appears to have an impact on GA catabolism, thus affecting the overall GA/ABA balance that regulates germination. QTL analyses were conducted to test whether previous candidate genes were located in a dormancy QTL, but also to identify new genes involved in dormancy. These analyses yielded several dormancy QTL and one of them located in chromosome 9 (qGI-9) was consistently detected even across environments. Fine mapping is already in progress to narrow down the number of candidate genes in qGI-9.

Genetic Dissection of Seed Dormancy using Chromosome Segment Substitution Lines in Rice (Oryza sativa L.)

“…Seed dormancy is a highly complex trait and largely influenced by genetic and environmental factors [4]. Recent progress in plant genomics and various genetic populations has facilitated the identification of quantitative trait loci (QTLs) for seed dormancy in many species, for example, in Arabidopsis [5], Lepidium sativum [6], oilseed rape [7], sorghum [8], barley [9], and wheat [10][11][12].…”

Whole‐genome resequencing‐based QTL‐seq identified candidate genes and molecular markers for fresh seed dormancy in groundnut

“…FSD/PHST/ in situ germination leads to a reduction in the grain or kernel yield and often attributes to medium to large yield losses and quality deterioration of the produce in both cereals (Abe et al, ; Benech‐Arnold and Rodríguez, ; Gao and Ayele, ; Nakamura, ; Rodríguez et al ., ) and legumes (Dias et al ., ; Patro and Ray, ; Vishwakarma et al ., ). Due to domestication and extensive human‐made selection during varietal development programs, modern groundnut represents much low genetic diversity compared to its wild ancestral species (which produces dormant seeds).…”

Targeted amplicon sequencing + next-generation sequencing–based bulked segregant analysis identified genetic loci associated with preharvest sprouting tolerance in common buckwheat (Fagopyrum esculentum)

“…Extensive work has identified genes or major dominant and recessive alleles for PHS tolerance in many plant species, such as wheat, barley, rice, sorghum, and Arabidopsis [28][29][30][31][32][33][34][35]. For example, QPhs.ocs-3A.1 (identified as MOTHER-OF-FT-AND-TFL1) in wheat, Sdr4 (Os07g0585700) in rice, and DELAY OF GERM INATION1 (AT5G45830) in Arabidopsis are dominant or semi-dominant [28][29][30].…”