The coconut pathosystem: weed hosts of nymphs of the American palm Cixiid Haplaxius crudus (Hemiptera: Fulgoroidea)

Lethal yellowing (LY) of coconut palm (Cocos nucifera L., Arecaceae) is a disease of economic importance that is caused by the phytoplasma ‘Candidatus Phytoplasma palmae’ and is transmitted by the planthopper Haplaxius crudus (Van Duzee) (Hemiptera: Cixiidae). This study explores the weeds used by H. crudus nymphs and other Cixiidae in a coconut pathosystem in southern Mexico. Nymphs were collected directly from the root system of each weed by hand or with the help of a vacuum after carefully opening the culm. This study included 11 species of weeds: nine Poaceae [Brachiaria decumbens Stapf, B. humidicola (Rendle) Schweick, B. mutica (Forssk.) Stapf, Digitaria abyssinica (Hochst. Ex A. Rich.) Stapf, Eustachys petraea (Sw.) Desv., Leersia hexandra Sw., Panicum laxum Sw., P. maximum Jacq., Paspalum notatum Flüggé]; one Cyperaceae [Cyperus ligularis L.], and one Portulacaceae: [Portulaca pilosa L.]. Brachiaria mutica, E. petraea, B. humidicola, P. maximum were identified as the principal host species for H. crudus nymphs. Brachiaria decumbens, D. abyssinica, and C. ligularis are new host records for the nymphs of H. crudus. Additionally, it was found that H. crudus may coexist with its cogeners H. skarphion Kramer (Cixiidae) and H. caldwelli Kramer (Cixiidae), on B. mutica. On C. ligularis, H. crudus may coexist with Oecleus snowi Ball (Cixiidae) nymphs. These results suggest that in the coconut pathosystem there is a complex of multitrophic interactions that should be considered in integrated management of LY.     

Further studies on the circadian rhythm in the proliferative activity of mouse intestinal epithelium

Zusammenfassung Im Tagesrhythmus der Proliferationstätigkeit von Darmepithelien wurde in drei verschiedenen Parametern um 02.00 Uhr ein Maximum gefunden. Mögliche Mechanismen werden erörtert.     

大连市银杏叶斑病病原菌鉴定

银杏(Ginkgo biloba L.)是常见的城市园林观赏绿化树种,并具有极高的材用、食用和药用价值.近年来,大连市银杏树发生了一种不明病因且较为严重的叶斑病,查明病因、为病害防治提供理论依据迫在眉睫.从病害发生严重区域采集叶斑病病叶样本,采用感病叶片单斑分离法,对分离菌株进行致病性测定、形态学鉴定及分子生物学鉴定等,对大连市银杏树发生的叶斑病进行了病原菌鉴定.结果表明,大连银杏叶斑病致病菌有2种,分别为链格孢属细极链格孢(Alternaria tenuissima)和链格孢(Alternaria alternata).迄今为止,细极链格孢(Alternaria tenuissima)侵染银杏导致其发生叶斑病鲜有报道.