In silico QTL mapping in an oil palm breeding program reveals a quantitative and complex genetic resistance to Ganoderma boninense.

Basal stem rot caused by Ganoderma boninense is the major threat to oil palm cultivation in Southeast Asia, which accounts for 80% of palm oil production worldwide, and this disease is increasing in Africa. The use of resistant planting material as part of an integrated pest management of this disease is one sustainable solution. However, breeding for Ganoderma resistance requires long-term and costly research, which could greatly benefit from marker-assisted selection (MAS). In this study, we evaluated the effectiveness of an in silico genetic mapping approach that took advantage of extensive data recorded in an ongoing breeding program. A pedigree-based QTL mapping approach applied to more than 10 years' worth of data collected during pre-nursery tests revealed the quantitative nature of Ganoderma resistance and identified underlying loci segregating in genetic diversity that is directly relevant for the breeding program supporting the study. To assess the consistency of QTL effects between pre-nursery and field environments, information was collected on the disease status of the genitors planted in genealogical gardens and modeled with pre-nursery-based QTL genotypes. In the field, individuals were less likely to be infected with Ganoderma when they carried more favorable alleles at the pre-nursery QTL. Our results pave the way for a MAS of Ganoderma resistant and high yielding planting material, and the provided proof-of-concept of this efficient and cost-effective approach could motivate similar studies based on diverse breeding programs. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-021-01246-9.

Time to be Ready to Void: A new tool to assess the time needed to perform micturition for patients with multiple sclerosis.

BACKGROUND: Urgency urinary incontinence is one of the major disabling urinary symptoms in people with multiple sclerosis (PwMS). The warning time (time from first sensation of urgency to voiding or incontinence) only partially reflects the possibility of continence. Other factors such as mobility, difficulties in transfer or undressing can influence this time. OBJECTIVES: The aim was to create a specific test for PwMS to assess the global time required to be ready to perform micturition and to assess its reliability. METHODS: The Time to be Ready to Void (TRV) was based on 2 timed steps: "mobility" stage, including standing up and walking 6m to the toilet, and the "settled" stage, starting as soon as the individual opens the toilet door until readiness for micturition. All participants performed the TRV twice. Reliability were assessed by the intraclass correlation coefficient (ICC) and convergent validity by Spearman correlation coefficient. RESULTS: We included 71 PwMS (mean [SD] age 54.4 [11.7] years). Inter-rater reliability was excellent for the TRV mobility stage (ICC: 0.97), settled stage (ICC: 0.99) and total test (ICC: 0.99). Test-retest reliability was good for the mobility stage (ICC: 0.88) and total test (ICC: 0.81) and moderate for the settled stage (ICC: 0.67). Test-retest reliability assessed by a Likert-type scale was good for each stage (κ 0.75 and 0.88). The mobility stage was correlated with the scores for the Timed Up and Go test, 10-Meter Walk Test, and Tinetti Mobility Test (ρ=0.89; ρ=0.88; ρ=-0.67, respectively; P<0.0001) and the settled stage with scores for the Tinetti Mobility Test, Functional Independence Measure and Nine Hold Peg test (right) (ρ=-0.48; ρ=-0.36; ρ=0.31, respectively; P<0.01). Comprehension, acceptance and relevance were rated good by most participants (97%, 95% and 90%, respectively). CONCLUSION: The TRV is a new tool to measure the global time needed to be ready to achieve micturition in PwMS. It seems useful in clinical practice for overactive bladder in addition to the classical warning time because it takes into account all the time needed to accomplish micturition (mobility, undressing, installation).

Structural analysis of cassiicolin, a host-selective protein toxin from Corynespora cassiicola.

Cassiicolin is a host-selective toxin (HST) produced by the fungus Corynespora cassiicola (strain CCP). It is responsible for the Corynespora leaf fall (CLF) disease, which is among the main pathologies affecting rubber tree (Hevea brasiliensis). Working on purified cassiicolin and using electron microscopy, we have demonstrated that this 27-residue O-glycosylated protein is able to induce cellular damages identical to those induced by the fungus on rubber tree leaves and displays the same host selectivity. The solution structure and disulfide pairing of cassiicolin have been determined using NMR spectroscopy and simulated annealing calculations. Cassiicolin appears to have an original structure with a prolate ellipsoid shape. It adopts an over-all fold consisting of three strands arranged in a right-handed twisted, antiparallel beta-sheet knitted by three disulfide bonds. Its conformation resembles that found in small trypsine-like inhibitors isolated from the brain, the fat body and the hemolymph of locust grasshoppers. But cassiicolin has no sequence homology with these protease inhibitors, and lacks their characteristic substrate-binding loop. Probably, this motif represents one of the few highly stabilized "minimal" scaffolds, with a high sequence permissiveness, that nature has selected to evolve over different phyla and to support different functions. The knowledge of the 3D structure opens the way to the delineation of the mechanism of action of the toxin using site-directed mutagenesis.

Purification and characterization of cassiicolin, the toxin produced by Corynespora cassiicola, causal agent of the leaf fall disease of rubber tree.

Cassiicolin, a phytotoxin produced by the necrotrophic fungus Corynespora cassiicola, was purified to homogeneity from a rubber tree isolate. The optimized protocol involves reverse phase chromatography followed by size exclusion chromatography, with monitoring of the toxicity on detached rubber tree leaves. Cassiicolin appeared to be a peptide composed of 27 amino acids, glycosylated on the second residue, with a N-terminal pyroglutamic acid and 6 cysteines involved in disulfide bonds. Its molecular mass was estimated to be 2885 Da. No significant sequence homology with other proteins could be found. The availability of pure toxin in sufficient amount is a prerequisite for its structure determination, which is a key step in the understanding of the aggression mechanism.

About Ganoderma boninense in oil palm plantations of Sumatra and peninsular Malaysia: Ancient population expansion, extensive gene flow and large scale dispersion ability.

Wood rot fungi form one of the main classes of phytopathogenic fungus. The group includes many species, but has remained poorly studied. Many species belonging to the Ganoderma genus are well known for causing decay in a wide range of tree species around the world. Ganoderma boninense, causal agent of oil palm basal stem rot, is responsible for considerable yield losses in Southeast Asian oil palm plantations. In a large-scale sampling operation, 357 sporophores were collected from oil palm plantations spread over peninsular Malaysia and Sumatra and genotyped using 11 SSR markers. The genotyping of these samples made it possible to investigate the population structure and demographic history of G. boninense across the oldest known area of interaction between oil palm and G. boninense. Results show that G. boninense possesses a high degree of genetic diversity and no detectable genetic structure at the scale of Sumatra and peninsular Malaysia. The fact that few duplicate genotypes were found in several studies including this one supports the hypothesis of spore dispersal in the spread of G. boninense. Meanwhile, spatial autocorrelation analysis shows that G. boninense is able to disperse across both short and long distances. These results bring new insight into mechanisms by which G. boninense spreads in oil palm plantations. Finally, the use of approximate Bayesian computation (ABC) modelling indicates that G. boninense has undergone a demographic expansion in the past, probably before the oil palm was introduced into Southeast Asia.

Diversity of the cassiicolin gene in Corynespora cassiicola and relation with the pathogenicity in Hevea brasiliensis.

Corynespora cassiicola is an important plant pathogenic Ascomycete causing the damaging Corynespora Leaf Fall (CLF) disease in rubber tree (Hevea brasiliensis). A small secreted glycoprotein named cassiicolin was previously described as an important effector of C. cassiicola. In this study, the diversity of the cassiicolin-encoding gene was analysed in C. cassiicola isolates sampled from various hosts and geographical origins. A cassiicolin gene was detected in 47 % of the isolates, encoding up to six distinct protein isoforms. In three isolates, two gene variants encoding cassiicolin isoforms Cas2 and Cas6 were found in the same isolate. A phylogenetic tree based on four combined loci and elucidating the diversity of the whole collection was strongly structured by the toxin class, as defined by the cassiicolin isoform. The isolates carrying the Cas1 gene (toxin class Cas1), all grouped in the same highly supported clade, were found the most aggressive on two rubber tree cultivars. Some isolates in which no Cas gene was detected could nevertheless generate moderate symptoms, suggesting the existence of other yet uncharacterized effectors. This study provides a useful base for future studies of C. cassiicola population biology and epidemiological surveys in various host plants.