Australasian Plant Disease Notes最新文献

Guava is a nutritious and profitable high-yield crop. Guava root-knot nematode (GRKN), M. enterolobii Yang & Eisenback, 1983 (= M. mayaguensis Rammah & Hirschmann, 1988), cause detrimental damage in guava orchards in more than 15 countries. Fifteen guava orchards in Homestead, Florida, were randomly sampled to check for potential plant-parasitic nematode damage to the trees. The guava RKN, M. enterolobii, was detected in 80% of the sampled orchards, causing damage to white and pink guava. Morphological and molecular analyses confirmed the identification of nematode species, and the host pathogenicity test showed the guava’s susceptibility to M. enetrolobii.

Extensive root galling observed on plantain (Musa spp., AAB) in Nigeria was analysed using Nad5 mitochondrial DNA sequences and the causal agent identified as Meloidogyne arenaria. Following the inoculation of population cultured, Koch’s postulates was fulfilled and the same symptoms observed. This provides the first molecular confirmation of M. arenaria causing such damage to plantain and highlighting its potential as a threat to the crop. Root knot nematodes are known to affect banana and plantain production but diagnosis of the species involved is only just being accurately determined with the recent improvements in molecular techniques.

The ryegrass cyst nematode, Heterodera mani, is reported from Western Australia for the first time. Cysts were recovered from soil samples collected on a broadacre cropping property near the town of Esperance. The production area is dominated by cereal/oilseed rotation and a species of annual ryegrass (Lolium rigidum) is a common weed issue in these paddocks. Morphometrics of cysts and second stage juveniles (J2s) from the Western Australian population were consistent with data from other reports of this species. Sequences of the mitochondrial cytochrome c oxidase I (COI) gene region were generated and matched those of H. mani from previous reports. Sequences of the large subunit ribosomal RNA (28S rRNA) were produced for H. mani for the first time. Although interspecific variation is relatively low for this gene in the Heterodera avenae species complex, our analyses indicate that 28S gene sequences sufficiently differentiate H. mani from other H. avenae-group members. Lolium rigidum is likely the host for the H. mani population discovered, although this requires further confirmation.

In a forest nursery located in Brazil, seedlings of Khaya spp. were observed showing leaf spot symptoms. From these symptoms, the phytopathogen Colletotrichum nymphaeae were isolated and characterized based on morphological, molecular and pathogenicity characteristics. To the best of our knowledge, this is the first report of C. nymphaeae infecting Khaya spp. in the world.

Asystasia gangetica (A. gangetica) leaves exhibiting yellow mosaic symptoms were tested for the presence of begomovirus infection. The putative full-length of a bipartite begomovirus components A and B molecules, respectively were amplified, sequenced, and analyzed. This represents a distinct begomovirus species infecting Asystasia in Benin Republic in West Africa.

Tomato yellow leaf curl virus (TYLCV) is the most devastating and globally spreading begomovirus (family Geminiviridae). Interestingly, until recently, it has not been reported from South Asia. In the current study, for the first time, we identified a novel strain of TYLCV and associated betasatellite infecting eggplant in Pakistan.

In Brazil, one blueberry plant of the cultivar Climax showing symptoms and signs of Pestalotiopsis spp. was observed in a commercial orchard. Morphological and molecular observations were consistent with those previously reported for Pestalotiopsis trachycarpicola (ex-type Pestalotiopsis trachycarpicola). Koch’s postulates were fulfilled. To the best of our knowledge, this is the first report of P. trachycarpicola (ex-type P. trachycarpicola) causing leaf spot of blueberry in Brazil.

In the current study, the complete genome of an isolate of cotton leaf curl Gezira virus (CLCuGeV), identified for the first time from Malva parviflora in Iraq, was amplified using rolling circle amplification and sequenced. The Iraqi isolate of CLCuGeV shared highest nucleotide identity at 98.2% with an Israeli isolate and clustered with isolates of the Egyptian and Cameroon strains in phylogenetic analysis.

A wild species of jute, Corchorus aestuans (family: Tiliaceae), was found to be infected root-knot nematode, Meloidogyne graminicola. The pathogenicity of M. graminicola on C. aestuans (local cultivar) under pot conditions showed that M. graminicola could infect, reproduce, and incite profuse root galling in C. aestuans. The initial inoculum of 10-second stage juveniles per 1000 cm3 of soil displayed the highest reproduction factor (P_f/P_i, RF = 145). Our findings demonstrated C. aestuans as a good host of M. graminicola, and its infection on roots exhibits typical terminal root gall with a distinct egg mass visible from the outside. To our knowledge, this is the first report of C. aestuans as a host of M. graminicola from West Bengal, India.

Aphelenchoides besseyi was detected as the causal agent of foliar dark spots on cowpea plants growing in the field, and its pathogenicity was confirmed. The identity of the nematode was determined through morphological, morphometric, and molecular characterization, using species-specific primers Abess_11F/Abess_11R targeting 28S rDNA, which amplified a fragment of 570 bp. This is the first report of A. besseyi parasitizing cowpea under field conditions in Brazil.