Componental analysis of the factors influencing resistance to sorghum midge, Contarinia sorghicola Coq.

Field studies were conducted in Andhra Pradesh, India, from 1982 to 1984 to determine components of resistance to the cecidomyiid Contarinia sorghicola in 4 resistant (DJ 6514, AF 28, TAM 2566 and IS I5107) and 2 susceptible (CSH 1 and Swarna) sorghum cultivars. Short floral parts, faster rate of grain development and a high grain tannin content were apparently associated with resistance to the cecidomyiid. Genotypic and phenotypic correlations between the resistance factors were in the same direction (positive or negative) as their association with resistance. Glume g2, lemma 12, anther and lodicule length, rate of grain development based on dry weight (except oviposition) and tannin content of mature grain showed correlation and path coefficients (direct effects) in the same direction, and were considered characters which could be useful criteria to select for resistance to the cecidomyiid. Using D² and canonical cluster analysis, the position of the cultivar AF 28 was distinct from other sources of resistance. However, based on the number of larvae/100 florets, the position of DJ 6514 was distant from TAM 2566 and IS 15107. Based on egg numbers, the number of adults emerged and grain damage, DJ 6514 was grouped with TAM 2566 and IS 15107. The position of the susceptible hybrid CSH 1 was generally distant from the self-pollinating susceptible variety, Swarna. It is concluded that the results indicated that sources of resistance to the cecidomyiid are diverse, and there is a distinct possibility of increasing the levels and diversity of resistance to this pes