Analysis of symbiotic microbial status of Atlantic sand dunes forest and its effects on Acacia gummifera and Retama monosperma(Fabaceae)to be used in reforestation

Atlantic forest natural soil flora was tested on two leguminous pioneer species Acacia gummifera and Retama monosperma to be used in rehabilitation programs of the coastal sand dunes forest of the Essaouira region.The rhizospheric soil of two endemic plant species:R.nonosperma and Juniperus phoenicea was sampled and split into two categories,one from native rhizospheric soil,the other of the sterilized rhizospheric soil.Investigation was focused on mycorrhizal formations,but other forms of beneficial symbiosis such as rhizobia and viable soil microflora were also studied.Growth and nutrition variables assessed included lengths of roots and shoots,number of branches,ratio of root to shoot dry mass and water,nitrogen and phosphorus levels.Results showed important mycorrhizal associations in roots of both plants,presence of nodules and abundance of viable soil microflora.J.phoenicea had a 100%frequency of mycorrhizal formation and an intensity of 80%compared to a frequency of 80%and intensity of 54%for R.monosperma.Nodules had the same density of CFU regardless of the origin.Abundance of viable microflora in rhisospheric soil of R.monosperma,J.phoenicea and the control differed significantly.Among the studied variables for A.gummifera and R.monosperma,nitrogen and phosphorus uptakes significantly wit the use of the nonsterilized rhizospheric soil.Both species doubled their phosphorus uptake when colonized by mycorrhizal species,R.monosperma doubled its nitrogen uptake and A.gummifera increased it by seven times compared with the control.No significant difference was noted for the other variables.

Diversity of Botryosphaeriaceae species associated with grapevine and other woody hosts in Italy,Algeria and Tunisia,with descriptions of Lasiodiplodia exigua and Lasiodiplodia mediterranea sp.nov

The diversity of Botryosphaeriaceae species associated with“Botryosphaeria dieback”of grapevine was investigated in 18 vineyards in Sardinia,Italy.Lasiodiplodia isolates obtained from different woody hosts including holm oak,sweet orange and broom bush in Italy,Algeria and Tunisia were also characterized.Morphological and cultural characteristics as well as ITS and EF1-αsequence data were used to identify the fungal isolates.Forty-eight botryosphaeriaceous isolates were obtained from 113 symptomatic grapevine samples,from which ten species were identified.Diplodia seriata was the dominant species(25%of isolates),followed by Neofusicoccum parvum(21.7%).Two species,Diplodia olivarum and D.africana are reported for the first time on grapevine.In addition,two new species namely Lasiodiplodia mediterranea sp.nov.from grapevine,holm oak and sweet orange and Lasiodiplodia exigua sp.nov.from broom bush are described.In artificial inoculation experiments conducted on excised green grapevine shoots and lignified canes as well as holm oak seedlings,L.mediterranea was shown to be an aggressive pathogen.

两个突尼斯细枝豆属植物亚种对干旱的适应性响应

干旱生境植物的生存和生态分布主要取决于水的可获得性以及植物抵御干旱的生理适应能力。在本研究中,我们比较了来自突尼斯的细枝豆属植物Retama raetam的两个亚种对干旱的生理响应,其中一种生长在沙漠气候下(raetam亚种),另一种生长于海岸带(bovei亚种)。为了对这两个亚种进行生理表征并揭示它们耐旱性的主要机制,从受干旱胁迫最长达一个月的四月龄植株中获取了多项参数,涉及植株的萌发、生长、光合作用(净光合速率、细胞内CO_(2)浓度、蒸腾速率、气孔导度和水分利用效率)和渗透物(脯氨酸、甜菜碱和总可溶性糖)积累等。研究结果表明,干旱会显著抑制植株的萌发、生长,对所研究的各项光合参数也都产生很大的负面影响。经过3周的处理后,bovei亚种受到了干旱条件的显著影响,其光合作用速率与对照相比最高下降了7倍。与此同时,该亚种中出现了对脯氨酸和甜菜碱的显著积累(相较于灌溉条件下的对照),但远低于raeMm亚种;在raetam亚种中,脯氨酸和甜菜碱分别增加至相应对照的24和6倍。综上所述,相较于生长在半干旱海岸气候下的细枝豆属植物种群,生长于沙漠地区的种群对干旱胁迫表现出更强的耐性,表明这种耐性在很大程度上取决于渗透物质在体内的累积。