Screening African Eggplant (Solanum Sp.) Accessions for Resistance to Bacterial Wilt (Ralstonia Solanacearum)

Abstract

African eggplant (Solanum aethiopicum, Solanum anguivi, and Solanum sp) in the Solanaceae family is an economically important crop produced in sub-Saharan Africa. It is an important vegetable used as a source of food and medicine. Eggplant is known for its genetic diversity in terms of agronomic traits and resistance to various diseases. Despite all these qualities, little has been done in Kenya especially its genetic resistance for the control of major devastating diseases (such as bacterial wilt) of solanaceous crops. African eggplant production like other solanaceous plants is limited by various yield and quality-reducing factors which include diseases, insect pests, and climatic conditions. Eggplant is susceptible to numerous soil-borne diseases; fusarium wilt, verticilium wilt, anthracnose fruit rot, and mainly bacterial wilt causing major economic losses. Control of the bacterium using chemicals, cultural methods, and biological control shows limited success due to its genetic nature, host range, and geographic distribution. However, the use of resistant plants has shown a considerable level of success in the management of the bacteria. Therefore, identifying resistant eggplant genotypes is an alternative for bacterial wilt management. The objectives of the present study were; (i) To determine the phenotypic reaction of African eggplant accessions to bacterial wilt infection and (ii) To identify Molecular markers for bacterial wilt resistance in African eggplant accessions. About 47 African eggplant accessions were collected (Solanum aethiopicum, Solanum aguivi, and Solanum sp.) from the African Vegetable Research and Development Center- Regional Center for Africa (AVRDC- RCA) in Arusha Tanzania. The accessions were prepared and separately sown in seed trays and at 4 true leaves were transplanted into a field whose BW history was predetermined and others were established in pots filled with sterilized soil in a greenhouse where they were mechanically inoculated. Symptom development was monitored and rated on a 1-5 scale for each accession and data was recorded weekly. Later 15 SSR markers were used to study resistance on eggplant accessions. Results showed that 13 accessions; RV100386, RV100234, RV100201, RV100245, RV100331, RV100250, RV100447, RV100161, RV100247, RV100240, RV100271, RV100458, and RV100342 were highly susceptible recording disease severity of 2.4 to 3.4. Also, resistant accessions, RV100264, RV100332, RV100265, RV100445, RV100453, RV100239, RV100438, RV100246, RV100242, and RV100455 showed disease severity of 1.1 to 1.2 during the study. Eggplant accessions were amplified by 5 markers (ecm009, emk03O04, SOL5036, emiO4P17, and ecm001). At least resistance markers were present in all the accessions tested. Accession, RV100455, Rv100242, RV100246, RV100438, RV100445, RV100453, RV100360 and RV100352 had resistance markers for bacterial wilt. Inconsistent reactions on the eggplant were observed whereby none of the accessions were immune, and even the symptomatic accessions carried resistant markers. In conclusion, this study showed that some eggplant accessions carried bacterial wilt resistance markers and can be utilized in breeding for BW-resistant varieties. The identified resistant genotypes can be adopted to manage BW to increase eggplant production.