Sorghum grain mold and anthracnose are two major diseases of sorghum
(Sorghum bicolor) that constrain sorghum production worldwide. Grain mold is caused
by several species of fungi, but the two most common are Curvularia lunata and
Fusarium thapsinum. Isolates of these two species were used to inoculate panicles of
selected sorghum cultivars in green house and field experimentations. Panicles were
sprayed at the time of anthesis with conidial suspensions of the two fungal species
individually or in a mixture and with water to serve as a control. Samples were collected
48 hours after inoculation for RNA extraction. In greenhouse studies, four cultivars
(Tx2911, Sureno, SC170 and RTx430) were used while thirteen cultivars were grown in
the field experiments. Gene expression was measured for the following genes using real
time polymerase chain reactions (rt-PCR): PR10, β-glucanase, chitinase, thaumatin,
sormatin, phenyalanine ammonia lyase (PAL), obtusifoliol 14α-demethylase (Obtus),
antifungal protein (AFP), apoptosis related protein (Apop) and leucine rich repeat
(LRR).
Seed germination tests in field grown cultivars indicated that germination rates
for SC279-14E, SC660 and Sureno were not greatly influenced by grain mold. Covering
the panicles with bags served to protect them against grain mold pathogens. The seed
mycoflora test showed that Fusarium thapsinum was the most frequently recovered
species and there were more species present in non-covered panicles.
The response of sorghum cultivars to grain mold infection involves multiple
defense genes. Real time PCR used to study the expression of sorghum defense in greenhouse grown plants showed that mRNA encoding PR-10, a small 10 kDa protein,
was highly expressed in the glumes and spikelets of resistant cultivars Tx2911 and
Sureno and constitutively in leaves. The expression of some other defense genes like
beta-glucanase, chitinase and AFP was variable. Sormatin was not expressed. Expression
of β-glucanase, chitinase, and PR10 was higher in field than in greenhouse experiments.
A second area of research involved tagging of a resistance gene for sorghum
anthracnose. Three AFLP markers (Xtxa607, Xtxa3181 and Xtxa4327) and three SSRs
(Xtxp3, Xtxp55 and Xtxp72) were identified. These markers were loosely linked to the
resistance genes. The markers are located on linkage group B. The results suggest that
markers located 20-30 cM on one side or the other of those tested should provide useful
tags for the resistance gene.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/85878 |
| Date | 10 October 2008 |
| Creators | Katile, Seriba Ousmane |
| Contributors | Magill, Clint W. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, born digital |
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