Grain-Filling Characteristics in Extra-Large Panicle Type of Early-Maturing japonica/indica Hybrids

Early-maturing japonica/indica hybrids (EJIH) have recently been released, performing a yield potential of 13.5 t ha−1 and greater yield increase over conventional japonica rice (CJ) and hybrid indica rice (HI) in production. More spikelets per panicle and improved grain-filling efficiency underlined the basis for the superior yield performance of EJIH. However, few studies are available on the panicle traits and grain-filling characteristics of EJIH, as well as their differences to CJ and HI. In our study, two EJIH, two CJ, and two HI cultivars with similar growth patterns were grown in the same fields. EJIH had a 12.2–18.8% increased (p < 0.05) grain yield relative to CJ and HI, mainly attributed to their higher daily grain yield. Although it had a lower panicle per m2, EJIH exhibited 28.0–38.3% more (p < 0.05) spikelets per m2 from an increase of 58.0–87.8% (p < 0.05) in spikelets per panicle than CJ and HI. Compared with CJ and HI, EJIH had a higher single panicle weight and more grains in the six parts of the panicle, especially in the upper secondary branches (US) and middle secondary branches (MS). EJIH exhibited a higher leaf area index (LAI), leaf area duration (LAD), leaf photosynthetic rate, and SPAD values after heading, which helped increase shoot biomass weight at heading and maturity and post-heading biomass accumulation. For CJ and HI, the grain-filling dynamics of grains in the six parts were all well simulated by the Richards equation. For EJIH, the grain-filling dynamics of grains in the lower secondary branches (LS) were well fitted by the logistics equation, with the Richards equation simulating grain positioning on the other five parts. EJIH had a lower mean grain-filling rate (GRmean) and longer days and grain filling amounts (GFA) during early, middle, and late stages than CJ and HI. Our results suggest EJIH gave a yield advantage over CJ and HI through a higher daily grain yield. The panicle traits and grain-filling characteristics differed greatly among the three cultivar types. Compared with CJ and HI, EJIH had lower GRmean and higher days and more grains in the panicle during early, middle, and late stages, which contributed to an increased GFA after heading, improved filled-grain efficiency, and higher grain yield.

A 31-bp indel localised in the 5' untranslated region of OsSUT3 affects the gene expression and rice (Oryza sativa L.) pollen development

OsSUT genes have been demonstrated to be relevant for diverse biological processes in rice. In this study, we identified the close relationship between a 31-bp insertion in a 5' untranslated region (5' UTR) of the OsSUT3 gene and higher OsSUT3 expression in rice panicles by qRT-PCR and transgenic research. Statistically significant results (P &lt; 0.01) were found for this 31-bp insertions/deletions (indels) in the rice pollen development and other panicle traits, such as the pollen number, pollen fertility, seeding rate, and grain length. An evolution analysis showed that the proportion of the 31-bp insertion significantly increases in rice domestication. Therefore, the 31-bp Indel could be considered as a convenient molecular marker to screen more pollen and better panicle traits in rice breeding.

Relationships between different morphological traits of panicles and seeds of Dactylis glomerata L. varieties

This study was aimed to evaluate morphological characteristics of the panicle as well as seeds of Dactylis glomerata varieties relevant for the assessment of seed production. Six varieties different in earliness were sown in two row spacing. Panicle traits: length, number of the 1st and the 2nd order branches as well as 1000-seed weight and morphological seed traits were assessed during 4-year utilization. Significant differences between varieties were found according to the panicle length, number of the branches and 1000-seed weight depending on the year of utilization as well as with reference to evaluated seed traits, irrespectively on year and row spacing. The results showed that the main traits determining the seed weight per panicle of Dactylis glomerata varieties are the panicle length and the number of the 1st order branches. Whereas, seed morphological traits had impact on 1000-seed weight and seed weight per panicle only in the second year of use, in which the highest rainfall than in the other years and moderate temperatures were recorded.