000			03710nam a22004697a 4500
001			G65851
003			MX-TxCIM
005			20240919020957.0
008			121211s ||||f| 0 p|p||0|| |
020			_a968-6923-93-4
040			_aMX-TxCIM
072		0	_aF30
072		0	_aH50
082	0	4	_a633.153 _bEDM
110	2		_aCentro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), Mexico DF (Mexico)
100	1		_9835 _aRibaut, J.M. _gIntegrated Breeding Platform _8INT1991 _uDeveloping Drought- and Low N-Tolerant Maize. Proceedings of a Symposium; El Batan, Tex. (Mexico); 25- 29 Mar 1996
245	0	0	_aChanges in allelic frequencies in a tropical maize population under selection for drought tolerance
260			_aMexico, DF (Mexico) _bCIMMYT : _c1997
340			_aPrinted
520			_aSelection for grain yield under severe water stress has often been considered inefficient because heritability generally declines as yield is reduced while environmental variance remains the same or increases. Under these conditions selection for secondary traits correlated with yield, Such as the anthesis- silking interval (ASI), may increase selection efficiency. Although ASI is a simple trait to measure in the field and has a relatively high heritability, it is not always possible to provide the stress levels required for efficient selection of this trait. CIMMYT physiologists conducted eight cycles of full-sib recurrent selection during the dry season for drought tolerance in the population 'Tuxpeño Sequia' based mainly on an index comprising increased grain yield and reduced ASI. In this study, we quantified changes in allelic frequencies over cycles of selection at loci of known map position. Through these changes identification of alleles involved in the expression of short or long ASI was possible, and may provide a rapid diagnostic tool in the future for screening lines or plants with potential drought tolerance in Tuxpeño germplasm. Changes in allele frequencies over cycles of selection (C0, C4 and C8; 116 plants randomly chosen from each cycle) were estimated using molecular markers. Loci distributed over the maize genome were assayed using RFLPs. Special attention was given to genomic regions responsible for expression of ASI, identified in a previous study using a cross between two inbreds derived mainly from Tuxpeño germplasm. There is strong evidence that the alleles of these two inbred lines are also present in this population. Allelic frequencies that either increased, decreased or remained stable were recorded for C8 relative to C0. Some major allele frequency changes were detected at loci located in genomic regions responsible for ASI expression, and the effects of these frequency changes were estimated. Implications of this analysis concerning the improvement of open-pollinated populations or lines using molecular markers are discussed.
536			_aGeneration Challenge Program
546			_aEnglish
591			_a9802|AGRIS 9702|anterior|R97-98PROCE|FINAL9798
593			_aJose Juan Caballero
594			_aINT1991
595			_aCPC
650	1	0	_aDrought resistance
650	1	0	_91081 _aDrought stress _gAGROVOC
650	1	0	_aFlowering
650	1	0	_aGenetic inheritance
650	1	0	_91211 _aPlant population _gAGROVOC
650	1	0	_aSelection
650	1	0	_aTropical zones
653	0		_aCIMMYT
650	1	0	_91314 _aZea mays _gAGROVOC
700	1		_aEdmeades, G.O., _ecoaut.
700	1		_aEdmeades, G.O.|Banziger, M.|Mickelson, H.R.|Peña-Valdivia, C.B. _eeds.
700	1		_aGonzález de León, D., _ecoaut.
700	1		_aHoisington, D.A., _ecoaut.
700	1		_aHuerta-Espino, J. _gGlobal Wheat Program _8CHUE01 _9397
942			_cPRO
999			_c3741 _d3741