From stress-tolerant populations to hybrids: The role of source germplasm - Mexico, DF (Mexico) CIMMYT : 1997 - Printed
The performance of populations experiencing water deficits at flowering and during grain filling or low N stress can be improved by recurrent selection, and the challenge now is to determine if those benefits carry over to hybrids which are derived from these populations. To test whether the frequency of stress-tolerant hybrids was increased by selecting inbred lines from stress-tolerant source populations versus conventional populations, we developed random inbred lines from four pairs of populations. Each member of the pair traced to a common population but differed in history of selection for stress tolerance. Drought tolerance was examined by comparing: TS6 C2 with Tuxpeño Sequia C0 and with Pop. 21 MRRS C2; La Posta Sequia C3 with Pop. 43 Cg, and Pool 26 Sequia C3 with Pool 26 C23. The effect of selection for low N tolerance was studied by comparing Across 8328 BN Cs with Across 8928. Each pair was sown in neighboring plots, managed identically, and selected in the same manner. For each population approximately 100 S2 families were selected. Inbred lines were each crossed to two conventionally selected inbred line testers, and topcrosses (TCs) were grown in 2-4 environments varying in the level of target stress. Under drought stress TCs derived from drought tolerant populations significantly outyielded those from conventional populations by an average of 22% (310 kg ha-1) at 1.56 t ha-1, nonsignificantly by 1% (43 kg ha-1)at 5.29 t ha-1, and yielded 2% less than the conventional TCs (-130 kg ha-1) under well-watered conditions (6.08 t ha-1). The probability of obtaining a hybrid that yielded 40% greater than the trial mean under severe stress was 4-fold greater when lines were extracted from a drought-tolerant source population than from its conventional counterpart. Topcrosses from Across 8328BN outyielded conventionally-derived lines under low N by a significant 11.1% (200 kg ha-1) at 1.90 t ha-1, and by a similar amount under high N (3%, or 200 kg ha-1) at 6.0 t ha-1. We conclude that drought- or N-tolerant elite source populations provide a greater proportion of drought- or N tolerant inbred lines and hybrids. This suggests that investment by CIMMYT and national programs in increasing the stress-tolerance of source and F2 populations formed during line recycling is fully justified.
633.153 / EDM