La estructura que compone al fenómeno del miedo

The phenotypic characterisation of ILL 2601 dissected the early habit of the Indian landrace into three major quantitative traits, namely time to emergence

(DTE) from sowing, days to flowering (DTF) from emergence, and the node of flower development (NFD). The latter was further dissected into two independent traits, node of floral initiation (NFI) and delay to flower development (DFD). The former is not responsive to prevailing photoperiod, while the later was only observed to occur under non-inductive long days in ILL 5588 (photoperiod-sensitive accession).

To probe the genetic basis for these traits, this chapter established a F2

population segregating for flowering time with ILL 5588. The segregants were genotyped and a genetic linkage map was constructed using DArT-SeqTM markers. Through QTL mapping it was determined that the earliness observed in ILL 2601 relative to ILL 5588 is a function of at least five different loci. Two loci were identified to contribute to the variation for the pre-emergent phase (DTE), and three loci, namely QTLA, QTLB, and QTLC (refer to 4.3.6.4), were identified to collectively contribute to the variation for time (DTF) and node (NFD) for the transition to flowering. It was also determined that DTE and DTF are independent of each other.

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4.4.1.1 Genetic control of the pre-emergent phase

The period of the pre-emergent phase, designated days to emergence (DTE) in this study, has not been reported in lentil to contribute to an early phenotype. The pre-emergent phase in lentil is described as the period between sowing and emergence (Roberts et al., 1986). QTL analysis for this trait determined two loci, namely DTE1 and DTE2, responsible for the observed variation for DTE. Moreover, it was determined that the loci are complementary and are likely to act on the same pathway. Furthermore, ILL 2601 alleles for both loci confer a shift to an early phenotype. Interestingly, no DTF or flowering node (NFD, NFI, and DFD) loci were determined to be co-located with either DTE locus.

Associated with germination time and seed dormancy, the genetic control of this trait is suggested to be regulated by a single dominant gene controlling the hard seed coat (Ladizinsky, 1985). Ladizinsky (1985) adds that this trait can be overcome by seed coat scarification. Roberts et al. (1986) has also suggested that in lentil this phase is controlled by the germination rate, which is determined to be a function of temperature (Covell et al., 1986).

However, in this study, the variation for DTE cannot be attributed to the seed coat as the seed coat tissue is of maternal origin and hence genetically F1.

Furthermore, as described in Section 2.1, all seed coats were scarified and seeds imbibed prior to sowing. This pre-sowing seed treatment further excludes the role of the seed coat in the observed variation for DTE.

Apart from work relating to the hard seed coat and its role in regulating the pre- emergent phase, there is no precedence for genetic work on germination time in lentil. In M. truncatula, one loci located on chromosome 8, (corresponding to lentil linkage group 7), and two loci on chromosome 5, (corresponding to lentil linkage group 5), have been previously implicated in the control of germination time, and the pre-emergent growth phase (Dias et al., 2011). Work in M. truncatula affords basis for future work in lentil relating to the molecular resolution of these DTE loci.

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4.4.1.2 Genetic control of flowering time and flowering node

The genetic basis for the early-flowering phenotype of the pilosae lentil is not known. It was determined in this study that the variation for flowering time and node in the ILL 2601 x ILL 5588 F2 population is controlled by multiple major loci,

with ILL 2601 alleles at QTLA, QTLB, and QTLC affording major shifts to an early flowering phenotype.

Observations of the photoperiodic response of ILL 2601 and ILL 5588, and QTL mapping for DTF, NFD, NFI, and DFD in this study point to a photoperiod- independent and a photoperiod-dependent basis for the control of the flowering phenotype. This implies that it is likely that multiple pathways for flowering occur in lentil, consistent with observations in other legume systems (Weller and Ortega-Martinez, 2015). This study also proposes that the altered regulation of each of these pathways by one or more loci can synergistically afford a shift in the flowering phenotype.

In this study, it was determined that the photoperiod-independent regulation of the flowering phenotype in lentil is controlled by a single locus at QTLA. QTLA

functions to regulate both the interval (time) between DTE and NFD, and the developmental node for NFI, while affording ILL 2601 a dominantly inherited early-flowering phenotype. It is not known how QTLA is regulated, or if polymorphisms in the ILL 2601 allele for QTLA result in a loss-of-function or a gain-of-function mutation, or if the locus is regulated by specific environmental stimuli. A photoperiod-independent, dominantly inherited early-flowering phenotype has been described by Jaudal et al. (2013) for M. truncatula. This will be explored in Chapter 5.

This chapter also identified that in the studied population, the photoperiod- dependent regulation of the flowering phenotype is a function of two epistatic loci, namely QTLB and QTLC. QTLB appears to regulate both the interval (time) between DTE and a fully developed flower, and the interval (node) between NFI and NFD (DFD). QTLC conversely is determined to only contribute to the

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variation for DFD. QTLB and QTLC are complementary to each other, and ILL 2601 alleles at either locus confer progeny an early flowering phenotype. Both loci complement the photoperiod-independent QTLA to synergistically shift the flowering phenotype. Chapter 3 determined that that the lentil Sn functions to confer photoperiod-sensitivity, and is an Arabidopsis ELF3 orthologue. In this chapter, the mutant elf3-1 was determined to not contribute to the photoperiod-insensitivity of ILL 2601. Chapter 5 will further explore the molecular basis for QTLB and QTLC.