000			01576nab a22003737a 4500
001			G33942
003			MX-TxCIM
008			121211b |||p||p||||||| |z||| |
040			_aMX-TxCIM
041	0		_aEn
043			_aUS
072		0	_aF30
090			_aREP-3988
100	1		_aPlucknett, D.L.
245	0	0	_aSustaining agricultural yields
260			_c1986
340			_aPrinted
500			_aGraphs, references p. 44-45
520			_aThe principles and scope of maintenance research are examined and the role of plant breeding in this research is considered. Maintenance research is seen as particularly important in maintaining the yield gains obtained from improved varieties, in combating evolutionary changes in crop pests, particularly in the tropics where reproduction occurs throughout the year, and in incorporating a range of resistance genes (rather than a single gene) into crops to produce a more durable resistence. Examples of breeding to maintain yields, for example through improved pest resistance, are taken from a range of crop breeding programs in a
546			_aEnglish
595			_aRPC
650	1	7	_aCrop yield _gAGROVOC _2 _91066
650	1	0	_aGenetic stability _91128
650	1	0	_aGermplasm conservation
650	1	0	_aResearch
650	1	0	_aResearch policies _91236
650	1	7	_aVarieties _gAGROVOC _2 _91303
650	1	0	_aYield components _91312
650	1	0	_aYield factors
650	1	7	_aPlant breeding _gAGROVOC _2 _91203
700	1		_aSmith, N.J.H., _ecoaut.
773	0		_tBioscience _n601480 _gv. 36, no. 1, p. 40-45
942			_cJA
999			_c12244 _d12244