A rubber tree’s durable resistance to Microcyclus ulei is conferred by a qualitative gene and a major quantitative resistance factor

Abstract

The components of genetic resistance from the Hevea brasiliensis cultivar MDF 180 against South American Leaf Blight (SALB) caused by Microcyclus ulei were investigated by QTL mapping. MDF 180 has already been described as a cultivar with a high level of partial and long-lasting resistance. The resistance of progeny individuals from a cross between a susceptible cultivar and MDF 180 was assessed both under controlled conditions of inoculation by three M. ulei isolates and under natural infection in a field trial. Genetic maps of the two parents of this progeny were mainly established based on microsatellites and AFLP markers. No resistance QTL were found in the susceptible parent. In the resistant parent, we identified a qualitative gene responsible for the resistance against isolates from French Guiana and a major quantitative resistance factor determining the resistance against isolates from the state of Bahia (Brazil). The qualitative resistance gene was denominated M15md and was located in the linkage group g15. Four minor resistance QTLs were also identified, two of which showed an epistatic interaction with M15md. The durability of the resistance of MDF 180 is discussed in light of these data.

QTL Mapping of Growth-Related Traits in a Full-Sib Family of Rubber Tree (Hevea brasiliensis) Evaluated in a Sub-Tropical Climate

“…The small size of some of the linkage groups indicates that the additional observed linkage groups may be the result of an incomplete coverage of the genome by the marker loci. A comparison of our results with the maps published by Lespinasse et al [9] and Le Guen et al [26], which used several markers, indicates that the identification of 18 linkage groups is possible. Furthermore, using only SSR and EST-SSR markers, Triwitayakorn et al [43] published a genetic linkage map in which the number of linkage groups exceeded the haploid number.…”

“…The estimate map contained 284 markers assigned to 23 linkage groups and spanned a total of 2688.8 cM; the previous map developed for the rubber tree was considerably smaller [9], more informative genetic linkage was determined because it was possible to use markers with segregation ratios of 1∶1:1∶1, 1∶2:1 and 1∶1 in order to estimate an integrated map, better results were achieved. Le Guen et al [26] and Triwitayakorn et al [43] developed a map for the rubber tree using markers with segregation in both parents, although this map was analyzed as a double pseudo-testcross.…”

“…Although many statistical methods have been specifically developed to perform QTL mapping in outcrossing species, the general double pseudo-testcross method is the most frequently used approach to studying the QTLs in rubber tree species [9], [25], [26].…”

Draft genome sequence of the rubber tree Hevea brasiliensis

“…The final genome assembly, based on only 27.86 Gb data or ~13× coverage after filtering repeat-matching reads (in Additional file 1: Table S1), resulted in scaffolds totaling 1,119 Mb with an N50 of 2,972 bp (Table 1). We anchored 143 scaffolds and the associated 1,325 genes onto the 18  H. brasiliensis linkage groups based on 154 microsatellite markers [17] (in Additional file 2: Figure S1). Within the mapped scaffolds, 74 additional reported markers were also identified (in Additional file 1: Table S2).…”

“…Based on the published linkage map [17], scaffolds were anchored and oriented into 18 linkage groups. Sequences for 154 microsatellite markers were obtained from public databases.…”