Genetic analysis of grain shape and weight after cutting rice husk.

Grain shape and weight are the most important components of rice yield and are controlled by quantitative trait loci (QTLs). In this study, a double-haploid population, derived from the cross of japonica CJ06 and indica TN1, was used to analyze QTLs for grain shape and weight under two conditions: normal growth with unbroken husk and removing partial husk after flowering. Correlation analysis revealed that these traits, except grain weight, had a connection between the two conditions. Twenty-nine QTLs for grain shape and weight were detected on chromosomes 1 to 3; 6; 8 to 10; and 12, with the likelihood of odds value ranging from 2.38 to 5.36, including 10 different intervals. Some intervals were specifically detected after removing partial husk. The results contribute to the understanding of the genetic basis of grain filling and growth regulation, and provide us some assistance for improving grain plumpness in rice breeding.

Identification and validation of a new grain weight QTL in rice.

The genetic control of grain weight (GW) remains poorly understood. Quantitative trait loci (QTLs) determining the GW of rice were identified using a natural GW mutant, sgw. Using a segregating population derived from sgw (low GW) and cultivar 9311 ('9311'; indica, high GW), the chromosome segment associated with GW was detected on the short arm of chromosome 7. To validate and further refine the locus, QTL analysis based on F2 and F3 populations was conducted, and a single major QTL (designated as qsgw7) affecting the 1000-grain weight of paddy rice was identified on the short arm region of rice chromosome 7 between simple sequence repeat (SSR) markers RM21997 and RM22015, where 4 bacterial artificial chromosome clones, OJ1339_F05, P0506F02, P0011H09, and P0519E12, were present. Analysis of the near isogenic line for qsgw7 (NILqsgw7) showed that the grain length, width, and volume of paddy rice in NILqsgw7 were significantly lower than those in '9311' and that the 1000-grain weight, grain length, width, volume, and chalkiness of brown rice in NILqsgw7 were significantly lower than those in '9311'. These results suggested that the qsgw7 gene, which was identified in this study, may be a new GW-related QTL that could affect GW and grain shape, especially grain plumpness.

Identification and Metabolism of 1-(Malonylamino)cyclopropane-1-carboxylic Acid in Germinating Peanut Seeds.

Peanut seeds (Arachis hypogea L. Yue-you 551) contain 50 to 100 nanomoles per gram conjugated 1-aminocyclopropanecarboxylic acid (ACC). Based on paper chromatography, paper electrophoresis, and gas chromatography-mass spectrometry, it was verified that the major ACC conjugate was N-malonyl-ACC (MACC). Germinating peanut seeds converted [2-(14)C]ACC to ethylene 70 times more efficiently than N-malonyl-[2-(14)C]ACC; when ACC was administered, most of it was metabolized to MACC. Germinating peanut seeds produced ethylene and converted l-[3,4-(14)C]methionine to ethylene; this ethylene biosynthesis was inhibited by aminoethoxyvinylglycine. These data indicate that MACC occurs in peanut seeds but does not serve as the source of ethylene during germination; ethylene is, however, synthesized from methionine via ACC.