Location: Subtropical Horticulture ResearchTitle: Identification of cocoa trees combining high yield potential and resistance to diseases in segregating progenies In Ecuador) Author
|Motamayor, Juan Carlos|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/11/2012
Publication Date: 10/15/2012
Citation: Amores, F., Ravelo, S., Suarez, C., Motamayor, J., Schnell, R.J., Gutierrez, O.A. 2012. Identification of cocoa trees combining high yield potential and resistance to diseases in segregating progenies In Ecuador. Meeting Abstract. 17th International Cocoa Research Conference, Yaounde, Cameroon, October 15-20, 2012. Interpretive Summary:
Technical Abstract: Diseases and low yielding planting material are the main factors limiting production of “fine” or “flavour” cocoa in Ecuador. This makes it necessary to develop modern varieties capable of overcoming these limitations. During the 1960s and 1970s INIAP tested several progenies from selected crosses between Nacional type selections and Upper Amazon genotypes. The main objective for these crosses was the recombination of genes to develop hybrid varieties with high productivity and disease resistance. It is in this context that five segregating populations from a similar number of crosses were planted at 4 x 4 m in 1969 at INIAP, E. E. T. Pichilingue in the zone of Quevedo. Altitude at the experimental site is 75 m above sea level. Annual temperature and rainfall averages for the last 25 years are 24.9°C and 2166 mm, respectively. Rainfall is marked by a seasonal pattern, with a dry season prevailing in the second half of the year. The soil classified as a Eutrandept is fertile and deep. For several reasons, data collection was sparse and discontinued for long periods of time making it difficult to draw valid conclusions. After a drastic pruning in mid-2002 to regain growth control by reducing tree height, crop management improved, making it possible to re-initiate data collection on a monthly basis from 2003 to 2008. Since earlier observations had demonstrated that the cross ‘EET 95’ (Nacional-type genotype) x ‘Silecia 1’ (Upper Forastero genotype) had substantially higher yield than the other populations, this population deserved close monitoring to search for superior trees that combine both high yield and disease resistance traits. With this aim in mind, the following variables were measured to assess individual tree performance: dry bean yield (mean 1.1 kg, range 0 to 7.1 kg); number of healthy pods (mean 18.2, range 0.8 to 102.2); number of diseased pods (mean 21.9, range 0.8 to 87.5); number of moniliasis-diseased pods (mean 11.3, range 0.2 to 65); percentage of moniliasis-diseased pods (mean 27.9 %, range 1.5 to 58.3 %;); number of witches´ broom-diseased pods (mean 10.6, range 0 to 36.7); percentage of witches´ broom-diseased pods (mean 27.4%, range 7.8 to 52.4 %); and number of vegetative witches´ brooms (measured once a year: mean 34.9, range 2 to 176). All figures reported are annual averages for the six year period. Trees coded A 179 and A 196 combined high yield potential and pod disease resistance in a consistent manner during the period of evaluation. They were selected for further development, as clones to fix the favorable traits exhibited. The genotype with the most extreme value of dry bean yield (7.1 kg) was not selected because the tree was growing at the edge of the plot, which may have caused an artificially high yield. Annual dry bean averages were 5.8 kg for A 179 and 4.1 kg for A 196. Moniliasis diseased pods reached 8.7 % and 6.9 % incidence while for witches´broom diseased pods the incidence was 15.7 % and 11.8 %, for A 179 and A 196, respectively. These percentages are substantially lower than respective population means. The disease resistance capacity of the selections is clearly appreciated when both trees are compared to A 745, with a high susceptibility to diseases (45.5 % and 29.2 % of the 65.2 pods it produced were destroyed by Moniliasis and Witches´ broom, respectively). Pod index values of 15.2 and 17.4 and seed index values of 1.63 g and 1.43 g were found for the selected superior trees. Pollination tests demonstrated that A 179 and A 196 are not self compatible, but they are inter-compatible. Further studies in large plots are ongoing because in the medium term there seems to be high potential to develop and release a biclonal variety for the benefit of farmers.