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The Eucalyptus plantation industry in Indonesia has expanded rapidly during the last few decades. During routine nursery disease surveys, symptoms of a leaf and shoot blight disease were detected on Eucalyptus mother plants. Isolates were obtained from symptomatic tissues and identified using DNA sequence analyses. Phylogenetic analyses showed that the isolates were those of Quambalaria eucalypti. Pathogenicity tests were conducted with isolates of Q. eucalypti on clones of E. pellita and E. grandis × E. pellita hybrids. These resulted in symptoms similar to those observed on naturally infected plants. Eucalyptus genotypes tested showed variation in their susceptibility, highlighting the potential to select and breed for resistance and thus to manage future outbreaks of the disease. This is the first report of the pathogen in Indonesia as well as in Southeast Asia. [ABSTRACT FROM AUTHOR]

Soybean (Glycine max L. Merr.) is the third food crop commodity after rice and maize in Indonesia. This plant is also known as the most important source of vegetable protein, which is relatively inexpensive, but a decrease in soybean productivity can occur due to infection with disease-causing pathogens, one of is Cercospora kikuchii which causes Cercospora leaf blight (CLB). The research objectives were to determine the anatomical resistance and disease severity of soybean cultivars against CLB. The method was an experiment with a completely randomized design (CRD) factorial pattern; factor 1 being soybean cultivars (Dering, Slamet, Grobogan, Wilis) and factor 2, namely pathogen inoculation (0 conidiospores/mL and 105 conidiospores/mL). Anatomical method preparations using paraffin, staining with 1% safranin. Disease criteria are based on the council of scientific and industrial research (CSIR) assessment method. Data were analysis used analysis of variance (p<0.05) and the least significance difference (LSD). The results showed that Dering and Slamet cultivars had the largest cuticle, epidermis, and palisade ratios and the smallest stomata length and width with the largest number of stomata and trichomes compared to Grobogan and Wilis. The disease severity (DS) of the cultivars Dering 14.6%, Slamet 24.64%, Grobogan 24.80% (classified as a resistant with low infection), while Wilis cultivar was 31.08% as a moderately susceptible cultivar with moderate infection. The novelty of soybean cultivar selection against CLB is important and its effectiveness for increasing soybean productivity. Dering, Slamet and Grobogan are likely to be further developed with their resistance to CLB disease. [ABSTRACT FROM AUTHOR]

Ganoderma boninense , the causal agent of basal stem rot (BSR) disease, has been recognized as a major economic threat to commercial plantings of oil palm ( Elaeis guineensis Jacq.) in Southeast Asia, which supplies 86% of the world's palm oil. High genetic diversity and gene flow among regional populations of 417  G. boninense isolates collected from Sabah, Sarawak, and Peninsular Malaysia (Malaysia) and Sumatra (Indonesia) were demonstrated using 16 microsatellite loci. Three genetic clusters and different admixed populations of G. boninense across regions were detected, and they appeared to follow the spread of the fungus from the oldest (Peninsular Malaysia and Sumatra) to younger generations of oil palm plantings (Sabah and Sarawak). Low spatial genetic differentiation of G. boninense (F ST  = 0.05) among the sampling regions revealed geographically nonrestricted gene dispersal, but isolation by distance was still evident. Analysis of molecular variance (AMOVA) confirmed the little to no genetic differentiation among the pathogen populations and the three genetic clusters defined by STRUCTURE and minimum spanning network. Despite G. boninense being highly outcrossing and spread by sexual spores, linkage disequilibrium was detected in 7 of the 14 populations. Linkage disequilibrium indicated that the reproduction of the fungus was not entirely by random mating and genetic drift could be an important structuring factor. Furthermore, evidence of population bottleneck was indicated in the oldest oil palm plantations as detected in genetic clusters 2 and 3, which consisted mainly of Peninsular Malaysia and Sumatra isolates. The population bottleneck or founding event could have arisen from either new planting or replanting after the removal of large number of palm hosts. The present study also demonstrated that migration and nonrandom mating of G. boninense could be important for survival and adaptation to new palm hosts.

Simple Summary: Palm oil is one of the main crops produced in Southeast Asia. However, the palm oil plantations within the region were severely affected by the basal stem rot (BSR) disease, caused by Ganoderma boninense. The disease causes substantial economic losses to oil palm producers, especially Indonesia and Malaysia. This review will cover the current knowledge on G. boninense published within the last 10 years. Plant pathogens are key threats to agriculture and global food security, causing various crop diseases that lead to massive economic losses. Palm oil is a commodity export of economic importance in Southeast Asia, especially in Malaysia and Indonesia. However, the sustainability of oil palm plantations and production is threatened by basal stem rot (BSR), a devastating disease predominantly caused by the fungus Ganoderma boninense Pat. In Malaysia, infected trees have been reported in nearly 60% of plantation areas, and economic losses are estimated to reach up to ~USD500 million a year. This review covers the current knowledge of the mechanisms utilized by G. boninense during infection and the methods used in the disease management to reduce BSR, including cultural practices, chemical treatments and antagonistic microorganism manipulations. Newer developments arising from multi-omics technologies such as whole-genome sequencing (WGS) and RNA sequencing (RNA-Seq) are also reviewed. Future directions are proposed to increase the understanding of G. boninense invasion mechanisms against oil palm. It is hoped that this review can contribute towards an improved disease management and a sustainable oil palm production in this region. [ABSTRACT FROM AUTHOR]

In 1911 and 1917, the first commercial plantings of African oil palm ( Elaeis guineensis Jacq.) were made in Indonesia and Malaysia in Southeast Asia. In less than 15 years, basal stem rot (BSR) was reported in Malaysia. It took nearly another seven decades to identify the main causal agent of BSR as the fungus, Ganoderma boninense . Since then, research efforts have focused on understanding G. boninense disease epidemiology, biology, and etiology, but limited progress was made to characterize pathogen genetic diversity, spatial structure, pathogenicity, and virulence. This study describes pathogen variability, gene flow, population differentiation, and genetic structure of G. boninense in Sarawak (Malaysia), Peninsular Malaysia, and Sumatra (Indonesia) inferred by 16 highly polymorphic cDNA-SSR (simple sequence repeat) markers. Marker-inferred genotypic diversity indicated a high level of pathogen variability among individuals within a population and among different populations. This genetic variability is clearly the result of outcrossing between basidiospores to produce recombinant genotypes. Although our results indicated high gene flow among the populations, there was no significant genetic differentiation among G. boninense populations on a regional scale. It suggested that G. boninense genetic makeup is similar across a wide region. Furthermore, our results revealed the existence of three admixed genetic clusters of G. boninense associated with BSR-diseased oil palms sampled throughout Sarawak, Peninsular Malaysia, and Sumatra. We postulate that the population structure is likely a reflection of the high genetic variability of G. boninense populations. This, in turn, could be explained by highly successful outcrossing between basidiospores of G. boninense from Southeast Asia and introduced genetic sources from various regions of the world, as well as regional adaptation of various pathogen genotypes to different palm hosts. Pathogen variability and population structure could be employed to deduce the epidemiology of G. boninense , as well as the implications of plantation cultural practices on BSR disease control in different regions.