Progress 10/01/09 to 09/30/10
Outputs
Progress Report Objectives (from AD-416) To integrate molecular genetic approaches and conventional breeding methods to develop improved germplasm for the California rice industry. Primary emphasis will be placed on the development of molecular (DNA) markers that can be used to predict the presence or absence of a trait of interest (e.g. disease resistance, cold tolerance) and the implementation of DNA marker-assisted selection to expedite the identification of useful germplasm and breeding of improved varieties. Approach (from AD-416) Continuation of the molecular genetic analysis of stem rot isolates that differ in their virulence; developing reproducible assays to quantify stem rot disease; complete analysis of the panicles collected in previous studies and classify the lines into maturity groups. Documents Reimbursable with CAL Rice Research Board. Log 40914. Agreement was established in support of Obj. 2 of the in-house project- The emphasis is on developing DNA markers to predict the presence of traits such as cold tolerance, disease resistance, and grain quality. These markers will accelerate breeding of improved varieties. A set of genes underlying several important traits was examined in CA varieties to determine if variation in these genes was present. Some rice genes impact yield directly by affecting grain number(Gn1a)and size(GW2 & GW5)or indirectly by controlling flowering and plant shape(Ghd7). Studies indicate that specific versions of these genes are found in high yielding varieties. Determining what versions are in CA varieties and breeding materials was the focus of our research. Both sequencing and marker analysis were employed. Calrose(�ancestral� line), S-102(short grain), M- 206 (medium), and L-202(long)were chosen for analysis. For GW5 which affects grain weight and width in some varieties, marker analysis revealed that only S-102 appears to have the gene form associated with greater grain width. Additional analysis revealed that most ancestral lines and 2 of 3 other short grain varieties appear to have the S-102 version of GW5. Since GW2 also affects grain size, the results of its analysis and the GW5 results will provide a more detailed picture of grain size in CA rices. Sequencing of Gn1a, GW2 & Ghd7 is underway. Starch is the primary component of milled rice. As such, its chemical properties directly affect the cooking, eating and milling quality. The genes involved in starch biosynthesis are well known, and a number of markers have been developed such as the commonly used Waxy gene markers. However, Waxy markers are not able to predict the cooking and eating quality of all rice lines. In FY10, DNA sequencing and marker analysis initiated to examine other starch biosynthesis genes(e.g., SSI, SSIIa, SBE1, SBE3) in CA varieties and some key Japanese germplasm. The ability of rice varieties to be crossed and produce highly fertile offspring is influenced by many genetic factors. The S5 gene is a key regulator of fertility and compatibility of indica-japonica rice hybrids. There are at least 3 versions of S5: japonica, indica, and wide-compatibility. Varieties with the japonica or indica forms generally produce offspring with poor fertility if crossed with varieties with the indica or japonica forms. Rice varieties with the wide-compatibility form will produce fertile offspring if crossed with either the japonica or the indica types. These wide-compatibility varieties act as a �bridge� between these two major rice types and may facilitate the transfer of desirable traits from indica rices to japonica rices, the type grown in the U.S. Initial analysis of 45 CA varieties indicates the presence of the wide- compatibility form of the S5 gene in the 7 long grain varieties. The use of wide-compatibility varieties or the transfer of this form of the gene into the desired germplasm is an important goal for future breeding efforts.
Impacts
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Publications
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