The diploid wild strawberry Fragaria nilgerrensis Schlechtendal ex J. Gay mainly distributed in Southwest China has many excellent traits and a small genome. A high-quality genome of F. nilgerrensis is available, but functional genomic research remains scarce. In the present study, to promote functional genomic research of F. nilgerrensis, ethyl methane sulfonate (EMS) was used to mutagenize the apical meristems, and the appropriate EMS mutagenesis dosages were screened. After treatment of 1200 apical meristems with 0.6% EMS for 6 h, a mutant library consisting of 86 mutant individuals, which were characterized by 17 mutant types, with a mutation rate of 7.17% was established. The characteristics of mutants included changes in the color, shape, number and size of leaves, and the architecture of flower and plant. The obtained mutants were identified by morphological appearance, botanical indexes, chlorophyll, photosynthetic fluorescence assays, root-tip chromosome, and flow cytometry observation. These mutants can provide great resources for gene functional research and future breeding of F. nilgerrensis.

Shorter grain-filling period and rapid endosperm development endow weedy rice (WR) with early maturity compared to cultivated rice (CR). However, the role of the cytological features and antioxidative enzyme system during grain development are largely unexplored. We selected four biotypes of WR and their associated cultivated rice (ACR) types from different latitudes to conduct a common garden experiment. The difference in the cytological features of endosperm between WR and ACR was compared by chemical staining, and the cell viability and nuclear morphometry of endosperm cells were observed by optical microscopy. Furthermore, antioxidative enzyme activity was measured during grain filling. Anatomic observation of endosperm shows that the development process of endosperm cell in WR was more rapid and earlier than that in ACR. The percentage of degraded nuclei of WR was 2–83% more than that of ACR. Endosperm cells in WR lost viability 2–6 days earlier than those in ACR. The antioxidant enzyme activity of WR was lower than that of ACR during grain filling. The ability of WR to scavenge reactive oxygen species (ROS) was weaker than that of ACR, which may contribute to the rapid cytological process in the endosperm cells of WR. The rapid cytological process and weaker ability to scavenge ROS in endosperm cells may contribute to early maturity in WR.

Chemical-dependent weed control has led to the evolution of herbicide-resistant weeds and pollution of arable land and water systems, posing a great threat to food security and environmental safety. For the first time, we developed a simple weed management regime to ecologically deplete the weed seed bank under a wheat-rice cropping system, which in turn allowed a reduction in the frequency of conventional herbicide applications while sustainably reducing weed infestation levels. The key ecological methods adopted here involve cleaning irrigation water by intercepting seeds at the water entrance and exit and removing floating weed seeds with a net during irrigation before rice planting, which significantly reduced the input of weed seeds into the seed bank. Quantitative analysis of the weed seed bank and population dynamics showed that implementation of this management regime consecutively for 6 years reduced the density of the total weed seed bank by 51% and the dominant grassy weed population density by 53% compared to those at the beginning. The effect of this ecologically sound weed control regime was comparable to that of conventional dual- or triple-application herbicide chemical control in each crop growing season. The results indicated that, compared with the conventional control method, the integrated weed management method could reduce the number of herbicide applications by half and reduce costs and labor by 30%. Furthermore, quantitative modeling analysis of the seed bank and population dynamics of the dominant weed species, Alopecurus japonicus, showed that continuous adoption of this ecological strategy could deplete the seed bank by more than 90%, thereby freeing the fields of the presence of this noxious weed.

Abstract Early maturity allows weedy rice (Oryza sativa L. f. spontanea) to persist by escaping harvest in paddy fields. A shorter grain-filling period contributes to the early maturity of weedy rice. However, the differences in morphology and endosperm development in the caryopsis between weedy and cultivated rice are largely unexplored. Here, we selected four biotypes of weedy rice and associated cultivated rice (ACR; Oryza sativa) from different latitudes to conduct a common garden experiment. The endosperm development process of the caryopsis was observed by optical microscopy and electron microscopy. Endosperm cell division and starch accumulation rate during grain filling were also measured. The grain development progress in weedy rice was more rapid and earlier than that in ACR. The endosperm development progress of weedy rice was 6 to 8 d earlier than that of ACR. The endosperm cells of weedy rice cellularized earlier and more rapidly than those of ACR, and the starch grains of weedy rice were more sharply polygonal and compactly arranged than those of ACR. The active endosperm cell division period in weedy rice was 4 to 7 d shorter than that in ACR, while the active starch accumulation period of weedy rice was 2 to 8 d shorter than that of ACR. The rapid development of endosperm cells and starch grains leads to the shorter grain-filling period of weedy rice. weedy rice.

BACKGROUNDEarly maturity is an important trait that is essential to the survival of weedy rice. To explore the mechanism of early maturity in weedy rice, the reproductive development of a large sample of weedy rice accessions and cultivars was compared in a common garden study. A selected sample of both weedy and cultivated rice was sown at different dates in two years to study in more detail their flowering and grain-filling patterns.RESULTSThe weedy rice from three major cropping regions matured 7-8 days earlier than their associated cultivars. Representative weedy rice accessions planted on conventional sowing dates flowered 3-26 days earlier than cultivars; delayed sowing caused divergence in the flowering regimes in weedy rice. However, regardless of the sowing date, weedy rice filled its grain 7-21 days faster than cultivars in both study years. Vegetative and reproductive traits of weedy and cultivated rice have different patterns of variation with delayed planting.CONCLUSIONEarly maturity is an essential factor determining the persistence of weedy rice by contributing to the escape of its seed from being harvested with the rice crop. Both early flowering and shorter grain-filling stages determine early maturity, and flowering is more plastic than grain filling. © 2017 Society of Chemical Industry.

Weedy rice (Oryza sativa L. f. spontanea), the same biological taxon as cultivated rice, is a noxious paddy weed, which seriously affected the yield and quality of rice. The early-maturity endows its dominant competition with cultivated rice causing serious crop yield losses. This characteristic of weedy rice has been re-ported, however, the mechanism has not been researched. Weedy rice and cultivated rice from Yangzhou, Taizhou, Maoming and Dandong were planted in the same field. The duration from sowing to heading, and from heading to maturity, the chlorophyll content and chlorophyll fluorescence parameters of flag leaf during grain filling between weedy rice and cultivated rice were compared. The duration from heading to maturity of weedy rice was shorter 10–33 days than that of respective cultivated rice. The flag leaf of weedy rice had lower chlorophyll content or aged earlier than cultivated rice. The photosynthetic performance index (PIABS), the max-imum quantum yield for primary photochemistry (φPo), the density of reaction centers per PSII antenna chloro-phyll (RC/ABS), the quantum yield for electron transport (φEo) and the probability that a trapped exciton moves an electron into the electron transport chain beyond QA- (Ψ0) of flag leaf of weedy rice reached peak at heading stage, then decreased gradually. And those of flag leaf of most cultivated rice increased from heading to milk stage and then decreased gradually. However, the PIABS, φPo, RC/ABS, φEo and Ψ0 of flag leaf of weedy rice all decreased slower than that of cultivated rice. The flag leaf of weedy rice senesced earlier than that of cultivated rice. The highest photosynthetic efficiency of weedy rice occurred earlier than that of cultivated rice. This may be one of the mechanisms of early maturity of weedy rice.

稻鸭共作能有效控制稻田杂草的危害,但是它对后茬小麦田杂草的影响及其控制作用尚没有详细的报道.我们于2000-2012年对江苏丹阳稻鸭共作兼秸秆还田的有机稻麦连作田土壤杂草种子库进行了连续13年的观察实验.结果显示,稻鸭共作兼秸秆还田的措施使看麦娘(Alopecurus aequalis)、通泉草(Mazus japonicus)、碎米荠(Cardamine hirsuta)等18种麦田主要杂草的种子库均有较大幅度的降低,总体的降低幅度高达97％.除了Pielou指数处于小幅波动状态外,麦田杂草群落多样性指数整体呈下降趋势.丰富度下降表明杂草种子库向种类少、多样性低的方向演变.从Bray-Curtis指数和Jaccard相似性指数也可以得到同样的结论.可见,连续稻鸭共作兼秸秆还田能够降低下茬的麦田土壤里杂草种子密度及多样性,控制杂草危害.