We report here the identification of a DNA marker closely linked to a gene for aroma in rice. The DNA marker was identified by testing 126 mapped rice genomic, cDNA, and oat cDNA, clones as hybridization probes against Southern blots, consisting of DNA from a pair of nearly isogenic lines (NILs) with or without the aroma gene. Chromosomal segments introgressed from the donor genome were distinguished by RFLPs between the NILs. Linkage association of the clone with the gene was verified using an F3 segregating for aroma. Cosegregation of the scented phenotype and donor-derived allele indicated the presence of linkage between the DNA marker and the gene. RFLP analysis showed that the gene is linked to a single-copy DNA clone, RG28, on chromosome 8, at a distance of 4.5 cM. The availability of a linked DNA marker may facilitate early selection for the aroma gene in rice breeding programs.

No abstract

No abstract

As a result of earlier breeding efforts, portions of the genome of "Basmati 370" have been introgressed into a rice breeding line, B8462T3-710. Cooked-kernel elongation was increased in this breeding line to a level equal to that of "Basmati 370". The objective of this study was to identify and locate quantitative trait loci (QTLs) associated with cooked-kernel elongation in an F3 population derived from a cross between B8462T3710 and the reduced-elongation recurrent parent variety, Dellmont. DNA from the parental lines and "Basmati 370" as a control, were screened for RFLPs using 170 clones chosen to cover the rice genome at intervals of 8 cM on average. Eighteen markers identified RFLPs common to Basmati 370 and B8462T3-710, but different from Dellmont, suggesting possible associations with kernel elongation. The B8462T3-710/Dellmont F3 population was analyzed for segregation of those RFLPs and for kernel elongation. Analysis of variance of the kernel elongation ratio revealed that two markers, 14.6 cM apart on chromosome 8, are significantly associated with this trait (RZ323 P ≤0.005, RZ562 P ≤0.05). Interval mapping suggests a single QTL with a close proximity to RZ323. This QTL was tested in F6 lines derived from the same cross and the presence of the B8462T3-710 segment detected by RZ323 caused a highly significant increase of the kernel elongation ratio (P ≤0.04). In addition, the QTL for kernel elongation and a gene for aroma, which are major components of the grain quality characteristics of Basmati-type rices, showed linkage. The availability of linked markers to the QTL may facilitate early selection for kernel elongation in rice breeding programs.

No abstract

No abstract

No abstract

Harvesting rough rice (Oryza saliva L.) at a low moisture content is one method of reducing energy needs for drying. The objectives of energy‐related research were to: 1) determine the economic feasibility of harvesting rice at a low moisture content; 2) identify the harvest moisture level at which head rice yield drops sharply; 3) identify rice cultivars adaptable for field drying; and 4) estimate energy savings to be gained by harvesting at particular moisture levels. Rough rice initially at 25% moisture content was harvested at 11 intervals during a time span of 30 to 36 days to determine the amount of drying in the field and the effect of field drying on grain yield, milling yield, germination, and test weight. Ten tests were run during four harvest seasons. Long‐grain cultivars, ‘Labelle’ and ‘Lebonnet’, and medium‐grain cultivars, ‘Brazos’ and ‘Nato’, were included in the tests. During each of the tests, rice moisture content dropped steadily during dry weather, but rain and dew caused unpredictable amounts of rewetting. Rice eventually dried to near 16% moisture content in all 10 tests and to 14% moisture content or lower in five of the tests. Grain yields were not greatly affected by delayed harvesting, but tended to decrease before the tests were concluded. The percentage of total milled rice (whole and broken kernels combined) increased with delays in harvest date, but the percentage of head rice (whole kernels of milled rice) reached a maximum at an intermediate harvest date, then declined rapidly with delays in harvesting. Both Brazos and Lebonnet cultivars required harvesting at a higher moisture content than did Labelle and Nato cultivars to maintain a high percentage of head rice. Neither germination nor test weight was adversely affected by delays in harvest dates. Energy for drying may be reduced about 50% by harvesting rice at 16% rather than at 22% moisture content.