Progress in our molecular biology program: molecular identification of spear rot tolerant genotypes
ASD has a modern molecular biology laboratory that is actively working in several fields and making use of these strong tools for ‘marking’ and protecting our most valuable genotypes (varieties and clones).
One major objective of ASD’s genetic breeding program is finding a genetic alternative to the spear rot problem in tropical America. Important progress was made in this area when we were able to associate tolerance to this condition with the tolerance that some genotypes express to biotic stresses, particularly water deficits and low temperatures. These traits were found in some crosses that had used mother palms selected from high and relatively dry lands of eastern Africa.
The work included the search for microsatellites associated with the spear rot tolerance observed in one such variety (Bamenda x Ekona) when compared to a standard variety with higher susceptibility (Deli x Nigeria). During the study, 30 palms approximately four years old were sampled for each variety and separated into three categories: healthy, diseased and recovering.
DNA was extracted using routine procedures established in our molecular biology laboratory and then it was subjected to amplification via PCR using 20 primers for the detection of the microsatellites (simple repeated sequences with a high level of polymorphism). The amplified fragments were separated by the ABI 3130 sequencer and then their size and ‘genetic distance’ were calculated.
The principal coordinates analysis, considering the varieties as groups, represented 61.1% of the observed variation and showed a separation between them; moreover, in both varieties susceptible individuals were separated within each group (healthy, diseased and recovering).
Principal coordinates analysis based on ‘genetic distance’, which shows the divergence between the Deli x Nigeria and Bamenda x Ekona varieties.
These results give an indication that the degree of polymorphism in each primer was suitable, because individuals with different phenotypic traits (tolerance and susceptibility) were segregated within a single population. The information obtained to date is a good start for more exhaustive research to determine the genetic profile of the parent palms and detect a genetic profile for the spear rot tolerance trait.
Partial view of ASD's modern molecular biology laboratory in Coto, Costa Rica