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Ophibolin A, a fungal sesterterpene, exerts a pivotal influence in a diverse array of biological processes, encompassing herbicidal, bactericidal, fungicidal, and cytotoxic activities. Sixty genes associated with sesterterpene compound biosynthesis were obtained from Bipolaris eleusines via transcriptome sequencing, and those closely linked to ophiobolin A biosynthesis were subsequently filtered. A gene encoding 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) that catalyzes the first committed step of ophiobolin biosynthesis in the mevalonic acid (MVA) pathway was isolated and characterized using RACE (Rapid Amplification of cDNA Ends) technology from ophiobolin A-producing fungus, B. eleusines. The full-length cDNA of the B. eleusines HMGR gene (BeHMGR) was 3906 bp and contained a 3474 bp open reading frame (ORF) encoding 1157 amino acids. Sequence analysis revealed that deduced BeHMGR had high homology to the known HMGRs from Pyrenophora tritici-repentis and Leptosphaeria maculans. It had a calculated molecular mass of about 124.65 kDa and an isoelectric point (pI) of 6.90. It contained two putative HMG-CoA-binding motifs and two NADP(H)-binding motifs. Induced expression analysis of the BeHMGR gene by methyl jasmonate treatment using quantitative fluorescence PCR showed that it significantly elevated after 3 h of methyl jasmonate treatment, peaked at 6 h, and then gradually decreased. This demonstrates that BeHMGR gene expression is induced by methyl jasmonate. [ABSTRACT FROM AUTHOR]

Zhefu 802 rice isogenic lines IG1, IG4, IG25 and IG26 have the same genetic background but different plant morphology. This paper studied their competition and allelopathy against barnyardgrass. The results showed that IG1 and IG4 had higher plant height, bigger tiller angle and less root vitality than IG25 and IG26, and provided 15% and 17% control of barnyardgrass plant dry weight, which were significantly higher than IG26. The competition ability of test rice isogenic lines against the weed was positively correlated with their plant height and tiller angle, but negatively correlated with their root vitality. The inhibition rate of the water extract of IG1 leaves on barnyardgrass root length was 77.6%, significantly higher than that of non-allelopathic material Xiushui 63, while the IG4 which has the similar plant morphology with IG1 didn't show any significant allelopathy. It seems that there were no correlations between allelopathy and morphological characters of rice under the same genetic background.

Weedy rice Luolijing (Oryza sativa) is generated in Dandong, Liaoning Province of Northeast China. Its plant height is taller than normal planted rice varieties, and its caryopsis is medium or long in size, which dropped easily after matured. The color of the caryopsis shell is straw-like or yellow alternated with black-gray. The spikelet is with or without awns, and the length of the awns is 2-12 cm. The 1000 caryopsis weight is 23.5 g, and the hull is nacarat. The seed germination rate at 13-38 degrees C is > 88%. Under 2.5-10 cm water flooding, the plant dry weight reduced 50%-69%. At seedling stage, Luolijing had a stronger resistance capability against barnyardgrass (Echinochloa crusgalli var. mitis) than an alellopathic rice I-kung-pao, which meant that Luolijing had no allelopathic function. The Luolijing had a tolerance to 0.5% saline-alkaline solution.

Rice allelopathy is implemented through its release of allelochemicals to environment. Many researchers considered that rice allelochemicals were phenolics. The action mechanisms of rice against weeds allelochemicals included the inhibition of seed germination and emergence, the effect on the balance of hormones, the damage on the integrity of cell membrane systems, the effect on photosynthesis and respiration, the disturbance of nutrient and water uptake and the effect on the protein synthesis and gene expression. Rice allelopathy is controlled by polygenes, and inherited quantitatively. Several QTLs were identified by the methods of molecular biological techniques and allelopathic bioassay. It might be the important research work to locate the QTLs accurately and to clone the allelopathic genes with the method of marker-assisted selection and the near isogenic lines.

138 rice (Oryza sativa) germplasms were identified to study the allelopathy to barnyardgrass (Echinochloa crusgalli), using the relay seeding technique. The results showed that Qingkun 2 from Jiangxi Province, Xiayitiao from Jiangsu Province, Jizaoxian from Anhui Province, Ganzaoxian 37 from Jiangxi Province, Shangnuo 1, IR68465-2-3-2 from IRRI, and Shuiyuan 2 from Korea had a strongly excellent inhibition effect on barnyardgrass. Results from pot culture showed that Gumei 2 and Zhong 156 had a greater inhibitory effect than control, and allelopathic material TN1 had no significantly inhibition effect, compared to non-allelopathic material Xiushui 63. The effect of Zhong 156 was related to its plant height, and significant different from that of Xiushui 63. Gumei 2 had a stronger inhibition effect on barnyardgrass, due to its own allelopathic trait.