Screening for plant resistance to sorghum head bug, Calocoris angustatus Leth.

Abstract

Sorghum head bug, Calocoris angustahlS Leth. (Hemiptera: Miridae) is an important insect pest of sorghum in the semi-arid tropics. A technique to screen for resistance to head bugs under fieid conditions was tested. Planting infester rows of susceptible cultivars (CSH 1 or CSH 5), 20 days before the test material or pianting early (4~5 days) fiowering lines (IS 802, IS 13429 and IS 24439) along with the test material, split planting oftest material at IS-day intervals, grouping test material according to maturity, and use of sprinkler irrigation to maintain high humidity, were found effective in increasing the efficiency of screening and selecting for resistance to head bUgs. A head cage technique to screen for resistance under no-cboice conditions has also been developed. Panicles Infested with 10 pairs of bugs at pre-and half-anthesis, result in maximum population build-Up and grain damage under headcage. This technique Is useful for confirming the resistance observed under field conditions. Under natural Infestation, five genotypes harboured relatively lower head bug numbers than the susceptible checks, but only three (IS 17610, IS 17618 and IS 17645) maintained their level of resistance under the headcage. Seed gemiBation was > 70% In these genotypes compared to < 10% in CSH 1 and CSH 5.

Evaluation of Some Sorghum Genotypes for the Susceptibility to Sorghum Head Bug Eurystylus Sp (Hemiptera; Miridae) in the Blue Nile State, Sudan

“…Tadesse (1986) reported that loose heads of traditional cultivars had a fewer head bugs, aphids and bollworm. Sharma and lopez(1992) reported, resistant genotypes have long glumes and cover the grain over a period of 20 days after flowering, compared with 6-8 days in the susceptible controls CSH I, CSH 5, and CSH 9.…”

Genotypic resistance in sorghum to head bug, Calocoris angustatus Lethiery

“…In preliminary screening, the entries were tested under infester row technique (Sharma & Lopez, 1991b). In preliminary screening, the entries were tested under infester row technique (Sharma & Lopez, 1991b).…”

“…Selected entries were tested under no-choice conditions using the headcage technique (Sharma & Lopez, 1991b). In the advanced trials, entries were planted in 2-row plots, and replicated twice in a randomized block design.…”

Genotypic effects of sorghum accessions on fecundity of sorghum head bug, Calocoris angustatus Lethiery

“…Head bugs collected from the field were reared on CSH 1 panicles (5 pairs/panicle) at the half-anthesis stage under the headcage to raise the insect culture for these studies (Sharma et al ., 1988 ;Sharma & Lopez, 1992a) . Twenty days after infestation, bugs were collected into 200 ml plastic bottles (5 pairs in each bottle) with an aspirator from the CSH 1 panicles, and were used for infesting different genotypes .…”

“…Grain damage in the infested panicles was evaluated on a 1 to 9 scale at maturity (1 = a few grains with feeding punctures, and 9= most grains with extensive feeding, tanning and showing more than 80% shriveling) (Sharma & Lopez, 1992a ; .…”