the Symposium on Wheats for More Tropical Environments - cimmyt

226interception for <strong>the</strong> month beforean<strong>the</strong>sis. Herein lies <strong>the</strong> answer to <strong>the</strong>question about maturity class; <strong>the</strong>cultivar needs to have "enough time(hence. sowing be early enough) toreach adequate light interception (i.e.,LAI > 3.0) no later than one monthbefore <strong>the</strong> optimum an<strong>the</strong>sis date. Sixtydays sowing-to-an<strong>the</strong>sis is just adequateif radiation is high and managementgood; a longer time may be neededo<strong>the</strong>rwise.The excellent work of De et al. (11).although at New Delhi just outside <strong>the</strong>tropics. illustrates this point. Sown onOctober 15. October 30 and November15. Kayansona (with o<strong>the</strong>r improvedcultivars) was earlier than <strong>the</strong> oldercultlvar C306 by 31. 24 and 4 days.respectively. Its yield was 46. 98 and30u=o 0-:-:g:a0. .... -S"t:l~25B~.§§ §~ ......Q) Q)::s::S 20l:)000~ 4000~~ 3000'>'c';l(; 2000---.----Photo<strong>the</strong>nnalQuotient;, ... - - - - --- ...,,;-................. ."",.,.;,. ....... .........Temperature.-­......~._._.. __.-. Radiation.........._./,-,--" 1966" ". __ !.~ ", (Beech and",' '" Nonnan)- ---':'}'''-~-..._- " , ,~;;o " ,, ,, ,~ ,~:\" ~" " ':\ ~U1.2 0"aNe.§Q)~1.0 ..c:: ......0 .......... o = Q)..c::::::0.80.. g0>1000Jun 1 July 1 Aug 1 Sep 1Date of an<strong>the</strong>sisOctlFigure 5. Long-term climatic averages. predicted grain yield from <strong>the</strong>seaverages and Equation 3. and actual yields for <strong>the</strong> best cultlvars andmanagement in two seasons at KUDUDurra. northwestern Australia (16°8lat.).Source: Beech and Norman (6)