Combined resistance of eggplant, Solanum melongena L., to leafhopper, Amrasca biguttula (Ishida) and the eggplant borer, Leucinodes orbonalis Guenee: terminal report

This four-year project involves the screening of eggplant and to identify and develop genetic stocks or stable plant populations of eggplant with combined resistance to leafhopper, Amrasca biguttula (Ishida) and shoot and fruit borer, Leucinodes orbonalis Guenee. The general unreplicated trials were done at the Central Experiment Station, UPLB during the dry season of 2000 and 2001. Confirmatory and replicated yield (under insecticide protected and unprotected conditions) and resistance trials fo the selected promising entries were conducted on the third and fourth year in farmers' fields in different eggplant growing regions in Pangasinan and Nueva Ecija and at CES, UPLB. With the concern on human and environmental safety, the search for safer ways to control pests and diseases is given priority. Also, the alarming dependence of farmers on pesticides to control this pest has challenged researchers to work on other methods of pest management. Today there is great effort at IPB to reduce pesticide use and shift to host plant resistance (HPR) and the integration of other compatible control tactics. The use of resistant varieties is regarded as the farmer's first line of defense against pests. This approach is one of the safest and most compatible with other control strategies. Considering such safety and compatibility, the concept of HPR-based crop-pest management strategy is being promoted and included as the final stage before any improved resistant varieties are released. This strategy is based on developing the improved variety under conditions compatible with HPR i.e. balanced management of weeds, very minimal use of pesticides and when applicable, diversified or multiple cropping conditions. Several genotypes from many sources were evaluated for resistance to the major insect pests. A number of native and wild relatives of eggplant were resistant to both and these materials could be utilized as parent materials for crop improvement work. These native varieties could also be used directly by the farmers for home consumption planted in the backyard or as a source of additional income when planted in commercial scale. Other promising entries were lines being developed by the IPB Vegetable Breeding Group. The top entries with leafhopper resistance based on several screening trials (in descending order) were A300 (now Mistisa), Abar, Parat, EG203, Mara and Acc 612. On the other hand, those entries with shoot/fruit borer resistance were EG203, Parat, Acc 612, A300 and 544 White. A-300 was moderately resistant to the fruit borer (Figures 4 and 5) and its yield was comparable to those of the high yielding hybrids. This variety is promising and if the breeders would be able to select an eggtype variety with good fruit characteristics that will attract the consumers, using A-300 as one of the parents, might produce a better variety. This accession was resistant to both pests but the fruit color which is light violet (near pink) with white stripes, may not be that attractive to the consumers. EG203 is also a promising variety, which could be used as parent material or be further improved for its horticultural traits especially the yield. Several crosses were generated and these were also evaluated for pest resistance. The segregating lines of Abar × A300 and C × A300 had the lowest nymphal and adult leafhopper counts at 30 DAT, Abar × DLP, A300 × Abar and PI-11 × GS1 at 45 DAT and A300 × Abar, 6 × Abar and 264a × Abar at 75 DAT. Abar and A300 consistently had the lowest number of leafhopper counts. Leafhopper resistance rating of almost all of the F1 crosses ranged from 1.0 to 2.6 indicating some level of tolerance against the leafhopper. No rating was taken on shoot/fruit borer due to problems on pilferage and heavy rains. Problems were encountered also in seed setting. It was not advisable to conduct hybridization work on rainy season. This part of the project was not continued duet to lack of funds and the replicated trials were given priority. Replicated trials for yield and resistance evaluation in farmers' fields for the promising entries showed that A-300 (Tisay), Abar and EG-203 were resistant to leafhopper while 544 White, Jackpot and Black Coral were susceptible to leafhopper in both Aliaga and Bantog sites. Abar and Jackpot were found susceptible to shoot/fruit borer. Casino, Acc 618 and Bingo gave the highest yields in both sites. Two lepidopterous insect pests namely the common cutworm, Spodoptera litura (Fabricius) and fruitworm, Helicoverpa armigera (Hubner) were seriously feeding on the whorl or shoot of the eggplant entries at vegetative stage and bore on fruits at building and fruiting stages in both experimental sites. These two pests are new records of eggplant. There were also nuisance pests encountered in the course of this project. The seedlings in the greenhouse were infected with an unidentified virus suspected to be cucumber mosaic virus and the papaya ring spot virus. The high infestation of two species of the flea beetles was also observed during maintenance and hardening in the greenhouse. The 28-spotted lady beetle and the unidentified leaffolder were present in Bantog and Aliaga during the replicated yield trials. During the second on-farm trials, results revealed that the leafhopper populations during this season under unprotected (unsprayed) conditions in Bantod, Asingan, Pangasinan were significantly less compared to the last previous years infestation level. The commercial hybrids Casino and Jackpot had the highest leafhopper counts while the native varieties Parat, Abar and A300 showed the lowest count. Despite the presence of leafhopper in the field, damage was low in most entries while damage was prominent on susceptible varieties. This may have been complicated by the extremely high population of the 28-spotted ladybird beetle. In the protected field, leafhopper population was low and the insecticide 'Actara' was found effective in controlling leafhopper. However, an unidentified leaffolder was observed damaging the leaves of vegetative stage. The yield in the protected plots was