Pollen Production in Theobroma cacao L. Genotypes National Type and CCN-51 and Its Relationship with Climatic Factors on the Ecuadorian Coast

Luz Cecilia García-Cruzatty,Freddy Zambrano-Gavilanes,Andrés Zamora-Macías,Luis Vera-Pinargote,John Cedeño-Ortega

doi:10.5586/aa.7323

Abstract

Cocoa is a primary source of economic income in the agricultural and agroindustrial sectors of Ecuador. However, cocoa crops are vulnerable to meteorological conditions that affect reproduction processes, including pollen production, which has encouraged the study of factors related to low crop yields and practical implications in breeding programs. The objective of this study was to assess the pollen production per flower in 11 genotypes of Theobroma cacao national type and CCN-51 clone. The number of pollen grains per flower was estimated by collecting 10 flower buds from each genotype for 12 consecutive months and directly counting pollen grains using an optical microscope and a Neubauer chamber. An average of 32,611 pollen grains per flower was estimated, with the largest amount of pollen (44,000) produced by the CCN-51 genotype. There was a moderate positive correlation between the environmental variables and pollen production (temperature, r = 0.33; p = 0.028; precipitation, r = 0.43; p = 0.0025). Since pollen production is an important indicator used for the selection of promising genotypes, the genotypes identified with the highest pollen production should be used in breeding programs.

Highlights

In Ecuador, cacao (Theobroma cacao L.) is one of the primary sources of economic income for the agricultural and agribusiness sectors
The (CV: 21.45) genotype group showed a mean of 32,914 ± 2,814 pollen grains per flower
Statistical difference between genotypes was verified (p = 0.0248), with CCN-51 being the genotype that produced the most pollen per flower (39,445 ± 13,549), followed by genotype L21-H43 (35,329 ± 8,875)

Summary

Introduction

In Ecuador, cacao (Theobroma cacao L.) is one of the primary sources of economic income for the agricultural and agribusiness sectors. Fine aroma cocoa accounts for only 6% of the world production. Latin America produces 80% of this total, with Ecuador contributing 54%, making it the largest producer of cocoa in the world (Acebo, 2016). The productive capacity of T. cacao will depend on the reproductive efficiency of forming fruits, flowers, pollen, and egg cells, which can be genotype specific (Mena & García, 2014). A higher quantity of pollen grains allows a more efficient dispersion and as a result, a more significant number of fertilized ovules, which commercially represent an increase in the seeds per fruit (Adjaloo & Oduro, 2013). The processes of formation and germination of pollen grains depend on environmental variables such as photoperiod, irradiation, precipitation, temperature, and relative humidity (García-Cruzatty, 2014)

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