Host‐plant preference and oviposition responses of the sorghum midge, Stenodiplosis sorghicola (Coquillett) (Dipt., Cecidomyiidae) towards wild relatives of sorghum

Abstract

Sorghum midge, Stenodiplosis (Contarinia) sorghicola (Coquillett) is an important pest of grain sorghum world-wide. Considerable progress has been made in screening and breeding for resistance to sorghum midge. However, some of the sources of resistance have become susceptible to sorghum midge in Kenya, in eastern Africa. Therefore, the wild relatives of Sorghum bicolor were studied as a possible source of new genes conferring resistance to sorghum midge. Midge females did not lay eggs in the spikelets of Sorghum amplum, Sorghum bulbosum, and Sorghum angustum compared to 30% spikelets with eggs in Sorghum halepense when infested with ®ve midge females per panicle under no-choice conditions. However, one egg was laid in S. amplum when infested with 50 midges per panicle. A larger number of midges were attracted to the odours from the panicles of S. halepense than to the panicles of Sorghum stipoideum, Sorghum brachypodum, S. angustum, Sorghum macrospermum, Sorghum nitidium, Sorghum laxi¯orum, and S. amplum in dual-choice olfactometer tests. The dierences in midge response to the odours from S. halepense and Sorghum intrans were not signi®cant. Under multi-choice conditions, when the females were also allowed a contact with the host, more sorghum midge females were attracted to the panicles of S. bicolor compared with S. amplum, S. angustum, and S. halepense. In another test, numerically more midges responded to the panicles of IS 10712 compared with S. halepense, whereas the dierences in midge response to the panicles of ICSV 197 (S. bicolor) and S. halepense were not apparent, indicating that S. halepense is as attractive to sorghum midge females as S. bicolor. The wild relatives of sorghum (except S. halepense) were not preferred for oviposition, and they were also less attractive to the sorghum midge females. Thus, wild relatives of sorghum can prove to be an alternative source of genes for resistance to sorghum midge. JAE 125 (2001)

The Chemical Ecology of Cecidomyiid Midges (Diptera: Cecidomyiidae)

“…No direct comparison was made of responses to synthetic blends and the natural stimulus (Birkett et al, 2004). Sharma and Franzmann (2001a) showed that C. sorghicola responded to color and odor of host plants, and also demonstrated differential oviposition on various wild relatives of sorghum (Sharma and Franzmann, 2001b).…”

Genetic structure and relationships within and between cultivated and wild sorghum (Sorghum bicolor (L.) Moench) in Kenya as revealed by microsatellite markers

“…The high genetic diversity could potentially be exploited in broadening the genetic base of sorghum breeding germplasm, while the unique diversity imply that wild sorghum is a potential source of novel genes such as pests and disease resistance. The genetic potential of wild relatives of sorghum, particularly as sources of resistance to pests and diseases, is well documented such as for sorghum shoot fly (Kamala et al 2009), sorghum midge (Sharma and Franzmann 2001), green bug (Duncan et al 1991), downy mildew (Kamala et al 2002) and ergot (Reed et al 2002). Moreover, the substantial genetic variability and differentiation revealed in sorghum landraces of Kenya should be incorporated in breeding programs by developing different populations with a broad genetic base.…”

Ecogeographical distribution of wild, weedy and cultivated Sorghum bicolor (L.) Moench in Kenya: implications for conservation and crop-to-wild gene flow

“…The potential of wild sorghum to provide new sources of resistance and adaptation in breeding programs have been established (Sharma and Franzmann 2001;Gurney et al 2002;Kamala et al 2002;Rao Kameswara et al 2003) but only partially explored. Conversely, crop-to-wild gene flow could result in the spread of genes from both domesticated and transgenic varieties into wild populations, and possible subsequent creation of aggressive weeds or invasive plants (Ellstrand et al 1999;Conner et al 2003), depending on the characteristics of the introgressed genes.…”