IDENTIFICATION AND TRANSFER OF HETEROTIC CHROMOSOME BLOCKS FOR FORAGEYIELD IN SHORT-DAY EXOTIC PEARL-MILLET LANDRACES

Photoperiod sensitivity of pearl millet, Pennisetum glaucum CL.) R. Br ., exotic accessions has limited their use in nontropical environments doe to excess height and late maturity problems. Objectives of this r esearch were (i) to describe and evaluate a modification of a direct m ethod to screen non-converted short-day Burkina Faso landraces (BFL) o f pearl millet for large heterosis-creating heterotic chromosome block s (HCBs) that can replace a small HCB in the male parent T383 of the t op producing F-1 hybrid Tifleaf 2 and to increase its forage yield; an d (ii) to determine the variation in the size of HCBs in a single land race. Short early T383-like F-2 plants in (BFL x T383) F-2 Populations were screened for HCBs by crossing them with T23Rp(1), which carries the red marker gene, crossing those F(1)s on T85A [cytoplasmic male st erile (ems) green 23], growing 100 spaced plants of the cross T85 x (B FL x T383) F-2, cutting and weighing 50 of the red and 50 of the green plants in each population, and analyzing the data with the SAS Genera l Linear Model. Percent heterosis for plant forage yield in 100-plant populations of each cross ranged from 0 to 51%. The average HCB hetero sis for T383 was 4%. Sister plants within a single BFL were variable e nough to make it important to cross a single BFL plant with T23Rp(1) t o measure HCB heterosis and with T265 (T383Rp(1)) to start the transfe r of the top HCB to T383. The modification method requires an extra ye ar before measuring HCBs, but requires a less variable 100-plant scree ning population and should require fewer backcrosses to transfer the t op HCB to T383.