| Echinochloa Beauv. has caused huge losses to rice production every year. Owing to thedifferent ways of cultivation and weeding, taxa of Echinochloa Beauv. are of high morphologicaland genetic variation, which increased the diiffculty of their identification, as well as the difficultyof their control in paddy fields. In order to classify the genus Echinochloa, and to elucidate theirdiversity, we collected seeds of206Echinochloa samples rfom main paddy regions of16provinces (Autonomous Region) of China, then sowed them in the same environment to obtaintheir offsprings. We then conducted the classification of the genus by using these offspringindividuals by using morphological and ISSR markers. The main results are as follows:(1)Eight groups were identiifed rfom206samples, corresponding to Echinochloarfumentaceae (2samples), Echinochloa oryzoides (5samples), Echinochloa crusgalli var.praticola (6samples), Echinochloa glabrescens (14samples), Echinochloa colona (2samples),Echinochloa caudate (16samples), Echinochloa cruspavonis (8samples), Echinochloa crusgallicomplex (150samples including Echinochloa crusgalli var. crusgalli，Echinochloa crusgalli var.mitis，Echinochloa crusgalli var. breviseta and Echinochloa crusgalli var. zelayensis) andrespectively, accounting for0.97%,0.97%,2.42%,2.91%,3.88%,7.77%，6.80%，72.81%and1.46%of the total sample number， respectively. Echinochloa crusgalli complex are the main taxaof the genus in the main paddy regions of China；(2)Analysis of vairance showed that the main species (and varieties) identification traits ofthe genus include leaf length, leaf width, panicle length, raceme length, awn length, spikelet length,ratio of length of first glume/spikelet length, diameter of main stem, plant height, spikelet color,branching of racemes, panicles bending, raceme compactness, form of lower parts of the plants;color of basal stems；(3)A key to the eight groups were given based on the morphological differences. E.frumentacea: grain readily deciduous at maturity; spikelets awnless and purplish; branches ofinflorescence incurving; E. oryzoides: Spikelets,4-6mm; leaf blades6-18cm long; E.glabrescens: lower lemma convex, hard and shining; E. colona: racemes neatly4-rowed, simple,openly spaced; spikelets awnless; E. crusgalli var, praticola: plant tall，150cm; spikelets2.5-3mm, dark purple; E. cruspavonis: awn of lower lemma15mm; racemes distinctly compound with many short branchlets; E. caudate: racemes simple, lower lemma awned, awn20mm;Echinochloa crusgalli var. crusgalli and its variety: awn of lower lemma absent or varying length.(4)Taxonomically, E. crusgalli var. praticola was suggested to be an independent speciesfrom E. cusgalli complex. For it has simple racemes, awnless spikelets，wider leaves, higher plants,and purple spikelets.(5)ISSR-PCR system of Echinochloa Beauv. was optimized by orthogonal experimentaldesign. The system volume was chose as20|j.L after comparing the inlfuence of different systemvolume on PCR results. The optimized system for Echinochloa Beauv. ISSR-PCR analysiscontained2^L lOxTaq buffer,0.5U/20p,L Taq DNA polymerase,150ng/20^iL DNA template,0.1jimol/L pirmer, and0.2mmol/L dNTPs. A total of nine primers for ISSR-PCR of EchinochloaBeauv. were selected, which are UBS808, UBS826, UBS827，UBS856, UBS857, UBS888，UBS889, UBS89, and UBS89). An optimal annealing temperature of each primer was determinedby using A temperature gradient PCR.(6)ISSR-PCR molecular analyses of53Echinochloa samples were conducted with theoptimized system.137ISSR bands were amplified by nine pirmers. Among them,136bandswere polymorphic, with a polymorphic rate of84.2%. Based on the data of ISSR marker, fifty-three Echinochloa samples were clustered into eight groups... |
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