Title : Effect of faba bean cultivars and sowing dates on Orobanche crenata biomass and seed reduction by the biocontrol agent Phytomyza orobanchia (Diptera : Agromyzidae)
Abstract:
The following points will be discussed • Economic importance of parasitic weeds Orobanche spp. • Problems that face faba bean crop in Egypt. • Biological control of Orobanche spp. • Resistant faba bean cultivars to Orobanche infection and sowing dates • Integrated Orobanche management Economic importance of parasitic weeds Orobanche spp. Broomrapes ( Orobanche spp. of the family Orobanchaceae ) are chlorophyll lacking holoparasites which attach to roots, causing great losses in quantity and quality in yields of the heavily infested host plants such as faba bean (Vicia faba L.), peas (Pisum sativum L), lentil (Lens culinaris Medic.), chickpea (Cicer arietinum L.), carrot (Daucus carots L.) and tomato (Lycopersicom esculentum Mill.) ( Parker & Riches, 1993 ). Orobanche crenata Forsk. is a very aggressive parasitic weed of winter legumes in the Mediterranean area of West Asia and North Africa ( WANA ), the area of infested faba bean totals nearly 200,000 hectare or about 63% of the planted area (Sauerborn, 1991a). Reported yield losses of infested faba bean ranged from 5% to complete crop failure depending mainly on the O.crenata seed bank in the soil, agronomic practices and temperature, as well as soil moisture regimes during the growing season (Borg 1986, Linke et al. 1991a, Sauerborn 1991b). Problems that face faba bean crop in Egypt. In Egypt, O.crenata is one of the major constraints to the production of faba bean, which is the most important food legume in breakfast and lunch diets ( El-Helaly et al., 1973 and Al-Menoufi, 1994, Al-Eryan and Zaitoun, 2015 ). In West Nile Delta region, the area infested with O.crenata was more than 25,000 feddan ( Zaitoun et al.,1991 ). It occurs in about 20 % of the total area cropped with faba bean, of which about half suffers low to moderate infestation ( less than 5 spikes per m² ) and the other half is infested with 5 - 20 spikes per m² or more. The loss in faba bean seed yield in El-Beheira governorate (West Nile Delta) was 20,000 tons or about 10 million dollars (Hassanein et al.,1996). Nowadays, Orobanche infestations forced Egyptian farmers to change faba bean crop by wheat or berseem and now Egypt introduce faba bean from outside. Biological control of Orobanche spp. Biological control is a particularly attractive means of suppressing parasitic weeds in crops.The insect natural enemies of Orobanche spp. have been surveyed in different countries. The dipteran Phytomyza orobanchia Kalt. ( Agromyzidae ) is the only one of these insects that has received further attention. This fly is widespread in Europe ( except Scandinavia ), the Mediterranean Basin and eastwards through Saudi Arabia to Uzbekistan (Spencer, 1973). P.orobanchia was first found in Germany and described by Kaltenbach (1872). In Egypt, it was first recorded by Hammad et al. (1967). In this respect, the broomrape fly, P.orobanchia may be considered as the main bio-agent against Orobanche spp. due to its mono-phagous habit, the larvae are active feeding on the immature seeds of Orobanche. A reduction of Orobanche seed production can only be achieved if the natural population of P.orobanchia is strengthened. This can be secured either by the creation of better conditions for P.orobanchia to reproduce and increase in number or by mass-rearing and targeted releases at the beginning of the Orobanche flourish ( Linke, 1999 andTrenchev, 1981). Field applications which have been developed in the former Soviet Union are the most suitable for bio-control of this parasitic weed. In Egypt, biological control trials of the weed Orobanche crenata was conducted by (kolaib, 1991; AlEryan, 1996; Al-Eryan and Zaitoun, 1998 & 2001; Zaitoun and Al-Eryan, 1999 and Abu-Shall, 2001). Although of the effectiveness of Phytomyza releases in reducing Orobanche seed production can reach 91.73%, the already infested soil in addition to new accumulated seeds will cause further infestations over the successive seasons. This finding should be undertaken in the future release programs of P.orobanchia (Abu-Shall, 2001 and Al-Eryan et al., 2004). 20 SEPT. 2019, Friday - 16:20 Page 66 Plant Science and Molecular Biology 4th Edition of Global Conference on GPMB 2019 Resistant faba bean cultivars to Orobanche infection and sowing dates: At the end of March 2004, broomrape, O. crenata spikes were collected from three faba bean cultivars ( Sabawy, Giza 3 and Egypt 1 ) during two sowing dates ( early in 1-15 October and late in 1-15 November ) at West Nile Delta. The size and weight of Orobanche parasite depend on the planted cultivars and sowing date, which reflects on the amount of produced seeds. Statistical analysis showed that Orobanche biomass significantly affected by faba bean cultivars and sowing dates. Results of this study should be undertaken during planning release programs to improve efficacy of P.orobanchia in Orobanche seed reduction. Integrated Orobanche management Control attempts on O.crenata have not been successful because the weed produces numerous resilient tiny seeds. Due to the intimate relationship of Orobanche with its host, herbicides can’t be applied without crop damage (Linke et al. 1990). Integrated control is therefore an attractive alternative for suppressing broomrape. In the Nile valley in Egypt, Nassib et al. (1989) and Al-Eryan et al. (2011) reported that integration of the use of the tolerant Faba bean genotype Giza 402 with a slightly reduced rate of glyphosate application (60g/ha) and slightly delayed sowing (The first fortnight of November) resulted in a nearly 96% reduction in Orobanche infestation and 29.2% increase in faba bean seed yield.
