SCREENING OF TREE COTTON (GOSSYPIUM-ARBOREUM) GERMPLASM TO GREY MILDEW CAUSED BY RAMULARIA-AREOLA

An experiment was conducted during 1985-89 to evaluate 1 489 germplasm lines of tree cotton (Gossypium arboreum L.) for their reaction to gr ey mildew caused by Ramularia areola Atkinson. Under natural condition s of disease occurrence, 24 lines were found free of infection. These infection-free lines. were tested further by artificial inoculation in screen-house and in field during 3 crop seasons of 1989-92, which rev ealed the presence of 7 immune and 17 highly resistant lines. The immu ne lines identified were 'Bangladesh', 'G 135-49' (G. arboreum L. race bengalense Silow), '30805', '30814', '30826', 30838' and '30856' (G. arboreum L. race cemuum Silow). Among 17 highly resistant lines belong ing to G. arboreum race bengalense, 7 ('AC 631', 'AC 727 DH', 'AC 727 MH', 'Desi 1', 'G 112', 'H 574' and 'K 53-519') showed desired staple length and 8 ('AC 24', 'AC 631', 'AC 727 DH', 'AC 727 MH', 'Desi 1', ' G 112', 'Gao-CB 3 NLL' and 'H 574') showed desired fibre fineness, whi ch were comparable with those of variety 'AKH 4'.