FIELD OF INVENTION

This disclosure provides a unique molecular marker in sorghum genome chromosome 7 for a gene that confers a broad range of fungal resistance trait, and the use of the molecular marker to manipulate resistance in sorghum. Particularly, a disease resistance gene called ANTHRACNOSE RESISTANCE GENE 1 (ARG1) and a negative regulator, i.e. antisense transcripts of ARG1, called CARRIER OF ARG (CARG) for the fungi resistance gene are knocked out within this quantitative trait locus (QTL).

BACKGROUND

Fungal disease are major challenges to crop production. Anthracnose is the leading global disease of sorghum. It is caused by the fungal pathogenColletotrichum sublineolum.

To fend off pathogen infection, plants have evolved immune systems that are effective in either restricting infection or inhibiting the progress of disease symptoms. The two primary branches of the plant immune system are PAMP Triggered Immunity (PTI) and Effector Triggered Immunity (ETI). PTI is a form of disease resistance initiated upon recognition of pathogen associated molecular patterns (PAMPs) by plasma membrane-anchored pattern recognition receptors (PRRs) located on the surface of plant cell membranes. Perception of PAMPs by PRRs activates a battery of immune responses, including the production of antimicrobial defense compounds, pathogenesis related proteins and accumulation of reactive oxygen species. This form of resistance is quantitative and often independent of the strain of the pathogen. Plant pathogens suppress PTI by deploying specific virulence effectors that interfere with PTI. In response, plants have evolved ETI, which is based on recognition of effectors by structurally related but polymorphic intracellular immune receptors known as nucleotide-binding site leucine-rich repeat receptors (NLRs). The core of NLRs is the nucleotide-binding (NB) and leucine-rich repeat (LRR) domains with N-terminal coiled-coil (CC) or Toll/interleukin-1 receptor (TIR) domains. ETI activates stronger plant immune responses that confer resistance to strains of the pathogen that express particular effectors. The strong selective pressure on pathogens imposed by ETI results in frequent defeat of resistance by pathogens that acquire new virulence effectors and thus escape recognition by NLRs. Recent observations suggest that PTI and ETI represent a continuum of overlapping responses rather than being categorical1.

Natural antisense transcripts (NATs) are non-coding RNAs widely known to regulate gene expression in animal and plant cells through several mechanisms2. Transcription interference between the expression of protein-coding sense transcripts and the corresponding NAT3,4, chromatin modification5, RNA interference, and DNA methylation have all been implicated in regulating expression of the sense transcripts6-8. In plants, NATs regulate phosphate homeostasis in rice9, cell wall biosynthesis in barley10cytokinin regulation in petunia11, salt tolerance and fertilization in Arabidopsis12, fiber development in cotton13and drought tolerance in maize14.

Sorghum is an important food crop but also serves as a source of animal feed, biofuel, and other industrial products. Sorghum anthracnose, caused by the fungal pathogenColletotrichum sublineolum(Cs), is the most devastating foliar disease of this crop15. Although anthracnose resistant germplasm is available, the specific resistance regulators and their mechanisms of function have not been determined. There is a need to identify these fungal resistance mechanisms sorghum plants use and exploit such mechanisms to generate broad spectrum resistance in the plant.

SUMMARY OF THE INVENTION

This disclosure provides an isolated polynucleotide comprising of SEQ ID NO:1 (ARG1) that confers sorghum broad spectrum resistance to fungi, wherein the polynucleotide is reversely embedded in SEQ ID NO: 2 (CARG).

This disclosure also provides primers to genotype molecular markers within sorghum genome to diagnose whether the sorghum has broad-spectrum fungal resistance trait. The primers for such diagnosis comprising sequences selected from the group of SEQ ID Nos:3-4, SEQ ID Nos: 5-6 and SEQ ID NO:9-10.

In some preferred embodiment, the aforementioned molecular marker is CARG with or without deletions of GGCGACCT.

In some preferred embodiment, the aforementioned the molecular marker is ARG1 with or without a premature stop codon.

This disclosure further provides a pair of primers to generate an expression cassette of antifungal ARG1 within sorghum genome, such primers comprising SEQ ID Nos: 7-8.

This disclosure further provides a method of generating a transgenic sorghum plant with broad resistance to fungi infection. The method comprising genetically transforming a susceptible sorghum genotype with the isolated polynucleotide of SEQ ID NO:1.

This disclosure provides a plant cell comprising the polynucleotide of SEQ ID NO:1.

In some preferred embodiment, the aforementioned plant is a monocot.

In some preferred embodiment, the aforementioned plant is wheat, barley, rice, maize, sorghum, oats, rye or millet.

This disclosure further provides a method of genotyping a plant. The method comprising using the pair of primers selected from the group consisting of SEQ ID NOs:3-4, SEQ ID Nos: 5-6 and SEQ ID NO:9-10.

In some preferred embodiment the aforementioned genotyping method uses primers generating a polymorphism fragment in PCR product that differentiates fungal infection susceptible versus resistant sorghum.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following figures, associated descriptions and claims.

