Correlation between Pollen Viability, Germination and Weather Conditions with Fruit Set in ‘Seedless’ ‘Den Khun Wang’ and ‘Bangkok Apple’ Guavas

Abstract

The study aimed to investigate the relationship between pollen viability, pollen germination, and climatic conditions and their effects on the fruit set of three guava cultivars: ‘Seedless,’ ‘Den Khun Wang,’ and ‘Bangkok Apple.’ The primary objective was to identify the causes of low fruit set in seedless guavas. Climatic conditions recorded included temperature, relative humidity, rainfall, and precipitation. Experiments were conducted on guava cultivars grown in field plots within the 7th Infantry Division area, Mae Rim District, Chiang Mai Province. Data analysis revealed a positive correlation between pollen viability and fruit set across all three cultivars (‘Seedless’ r = 0.755; ‘Den Khun Wang’ r = 0.690; ‘Bangkok Apple’ r = 0.706). Each cultivar exhibited peak fruit set during distinct periods. ‘Seedless’ guava in August (56.54%), ‘Den Khun Wang’ in October (71.43%), and ‘Bangkok Apple’ in April and June (42.77% and 40.00%, respectively). Climatic factors also showed consistent positive correlations with fruit set across the cultivars, including relative humidity (‘Seedless’ r = 0.246; ‘Den Khun Wang’ r = 0.296; ‘Bangkok Apple’ r = 0.343), rainfall (‘Seedless’ r = 0.383; ‘Den Khun Wang’ r = 0.322; ‘Bangkok Apple’ r = 0.457), and precipitation (‘Seedless’ r = 0.356; ‘Den Khun Wang’ r = 0.232; ‘Bangkok Apple’ r = 0.363). These findings highlight the significant influence of climatic factors on guava fruit set and suggest that effective production planning based on climatic data could improve yields in the studied cultivars.