Detection and Molecular Characterization of Phytoplasma associated with Lethal Yellowing Disease of Coconut Palms in Cuba

Lethal Yellowing (LY) disease of coconut palm (Cocos nucifera L.) in Cuba has been reported since the end of the 19th century. In order to ascertain the presence of phytoplasmas associated with this disease, leaf samples were taken from plants showing typical disease symptoms and assayed for the LY agent by the polymerase chain reaction (PCR) using LY‐specific primers. Selected PCR amplification products were cloned, sequenced and compared to that of a Mexican LY isolate from the Yucatán region. The results obtained confirm the presence of LY phytoplasma in Cuba. Cuban and Mexican isolates show an overall high degree of sequence similarity with occasional point mutations and small deletions or insertions. Based on these identified genetic differences, LY isolates from the Havana and the Yucatán region cluster together and apart from isolates originating at Maisí in eastern Cuba.     

Phenotypic and genotypic diversity among strains of <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis> in comparison with related species

Intra-specific diversity of 200 Aureobasidium pullulans strains isolated from different sources and their relatives Kabatiella lini CBS 125.21 T and Hormonema prunorum CBS 933.72 T were studied by assessment of macromorphological, and physiological tests, sodium dodecyl sulfate-polyacrylamide gel electrophoresis technique (SDS–PAGE) of whole-cell proteins as well as enterobacterial repetitive intergenic consensus (ERIC)-, repetitive extragenic palindromic (REP)- and BOX-PCR techniques (collectively known as rep-PCR). Rep-PCR is an efficient procedure for discrimination of A. pullulans in terms of simplicity and rapidity. RFLP-PCR technique was applied for the identification of A. pullulans isolates and distinction from related species. This technique was insufficient for investigation of intra-specific diversity. The tested strains of A. pullulans could be divided into two groups based on their macromorphological, protein patterns obtained after SDS-PAGE as well as rep-PCR patterns. The first group of strains shared similar characteristics and was very different from the second one, designated as “complex group”, consisting of strains with very little similarities within the group. Phenetic analysis of ERIC banding patterns failed to group the isolates on the basis of their substrate or geographical origin. Using 18S rDNA gene sequence analysis of selected isolates, three strains: HoHe3 km, A. pullulans DSM 62074 and H. prunorum CBS 933.72 T were distinguished from all other analysed members of genera Aureobasidium and Kabatiella. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Changes in morphological traits of the cabbage aphid (<Emphasis Type="Italic">Brevicoryne brassicae</Emphasis>) associated with the use of different host plants

The genetic and morphological differentiation of insect populations in relation to the use of different host plants is an important phenomenon that predates ecological specialisation and speciation in sympatric conditions. In this study, we describe the morphological variation of populations of Brevicoryne brassicae (Homoptera: Aphididae) associated with two host species, Brassica oleracea and Brassica campestris, which occur sympatrically in the highlands of Chiapas, Mexico. The study is aimed at obtaining evidence regarding phenotypic differentiation induced by, or associated with, the use of distinct but closely related host species. Seven morphological characters were measured in 696 wingless aphids collected from plants of the two host species at four localities. Morphological variation was summarised through principal components analysis (PCA). Sixty-two percent of morphological variation was explained by the first two PCs. The first component (PC1) was related to the general size of appendages, and PC2 was interpreted as the relationship between body size (body and leg size) and antenna length. Aphids growing on B. campestris were bigger than those collected from B. oleraceae. Significant differences between hosts were detected for PC1, whereas a significant effect of locality, host, and the interaction locality × host was detected for PC2. These results indicate that the average phenotype of B. brassicae individuals inhabiting different host-plant species differs as a consequence of the contrasting feeding environments the host species provide.