Fruit traits associated with resistance to fruit pests of hot pepper in Uganda

A dissertation submitted to the Directorate of Research and Graduate Training in partial fulfilment of the requirements for the award of a Master of Science in Crop Science of Makerere University

Hot pepper (Capsicum spp) is an important economic crop for small-scale farmers. However, its production and profitability is hindered by infestations of fruit flies and the invasive false coddling moth (FCM). These fruit damaging pests are of quarantine importance and face stringent restrictive regulations imposed by importing countries. Farmers in effort to protect their produce, resort to use pesticides, albeit inappropriately. This increases the likelihood of rejection of export produce at the international market due to the failure to meet acceptable maximum pesticide residue levels in export produce. Pests can cost effectively be managed by exploiting host plant resistance which can also easily be used with other management practices. The main objective of this study was to improve the competitiveness of Ugandan hot pepper exports on the international market by developing knowledge for use in host plant resistance against quarantine fruit pests. To achieve this, studies were conducted to; a) assess the levels of resistance of hot pepper genotypes of different Capsicum spp to fruit pests; b) establish morphological fruit traits associated with resistance to fruit pests’ infestation and to fruit yield. A total of fifty-one (51) hot pepper genotypes, thirty-seven (37) local and 14 exotic, were screened for resistance against fruit pests under field conditions at Makerere University Agricultural Research Institute Kabanyolo (MUARIK) from 2016 to 2018. Fifteen genotypes were further evaluated on farm in Ibanda district. Data were collected on fruit damage, fruit fly, and FCM infestation and fruit traits (fruit weight, length, width, flesh penetrability, and fruit wall thickness) and yield. Results showed variation in performance of the hot pepper genotypes, in terms of resistance to fruit pests’ infestation and yield. Genotypes CAP0408-12, UG-WE02-1014, UG-WE02-0711, UG-EA06-0515 and UG-WE02-1608 were the most promising in terms of resistance to fruit flies though they had low yields. Genotypes UG-WE02-1802, UG-WE02-1909, UG-CE01-0401, UG-WE05-0607 and UG-CE01-0805 had the highest yields but were more susceptible to fruit damaging pests. Fruit fly infestation correlated positively and significantly with number of fruit fly larvae, average fruit weight, fruit length, fruit width, and fruit penetration force (r=0.56, r=0.59, r=0.30, r=0.63, and r=0.24, respectively). False coddling moth infestation similarly correlated to average fruit weight, fruit length, fruit width (r=0.50, r=0.17, r=0.50, respectively), but had no significant relationship with penetration force. Size (fruit width and weight) was the major fruit trait that influenced pest infestation of the genotypes. Generally, heavy and broad hot pepper fruits were more prone to infestation by the fruit pests. Genotypes, CAP0408-12, UG-WE02-1014, UG-WE02-0711, UG-EA06-0515 and UG-WE02-1608 showed substantial resistance to both fruit flies and the false coddling moth. Therefore, they should be followed up for utilization in breeding programs for their resistance to the studied fruit pests.

Africa-Brazil Agricultural Innovations Marketplace/project #2685