the Symposium on Wheats for More Tropical Environments - cimmyt

134locations. are selected for yield trials.Although <strong>the</strong> apparent ability of anygiven line to perform well under onlyirrigated or dryland conditions wouldnot necessarily exclude it from fur<strong>the</strong>rconsideration. it would have to beselected at ei<strong>the</strong>r all <strong>the</strong> irrigated or all<strong>the</strong> dryland sites.Lines selected from <strong>the</strong> BSN are testedfor three years in experiment stationtrials which are planted at bothfavorable and late dates of planting. andunder both irrigated and drylandconditions. Selection criteria. inaddition to those mentioned above.require that a line must perform as wellas Sonalika at a late date of planting.and better if planted at a favorable dateunder irrigated and/or drylandconditions. Lines advanced through <strong>the</strong>third year of trials are grown <strong>the</strong> fourthyear in large unreplicated plots on bothfanners' fields and experiment stations.This stage is critical; for a line to bereleased by <strong>the</strong> National Seed Board. itsgood performance must be observed in<strong>the</strong> field by a committee selected by <strong>the</strong>Board.This strategy may appear complicated;however. as a result of <strong>the</strong> stringentselection criteria, <strong>the</strong> number of linesadvanced annually are diminishedconsiderably. <strong>the</strong>reby redUcing <strong>the</strong>amount of material that must behandled in trials. For example. in <strong>the</strong>third-year trials of 1984-85. only tenlines including checks will be entered.In any case. it is felt that this strategy ispracticable. since it shows thatgermplasm with <strong>the</strong> required fleXibilityis available.Recently released varieties. on <strong>the</strong>average. yield 10% more than Sonalikaif planted at a favorable date, and aswell as Sonalika when planted late. Allhave maturities of three to seven dayslater than Sonalika. and all perform aswell and often better under water-stressconditions than Sonalika. Thesevarieties. in fact. were developedwithout employing <strong>the</strong> above strategy;it appears. however. that <strong>the</strong> presentprogram will streamline <strong>the</strong> selectionprocess and make possible <strong>the</strong> earlyidentification of appropriate material.