Board, James E. : James E. Board, formerly Post Graduate Research Agronomist, University of California, Davis, is now Assistant Professor of Agronomy, Louisiana State University, Baton Rouge, LA 70803.

Peterson, Maurice L

Davis trials ) . Hot areas sustain temperatures Floret sterility , commonlycalled blanking , above has been recognized as a problem in Califor - 95 O F at flowering ( Kern County ) . The sterilityperformance of M - 101 and M9 nia rice production for a considerableperiod . was reversedin the Davistrials ( cold ) . The ef - Surveys in 1971 and 1972 showed average fect was especially pronounced in the early sterility of 12.5and 12.8percent , respectively . Davis trial , which was afflicted with cool im - Data from tropical areas also indicate an av - gation water , resulting in colder canopy tem - of 10 to 12 percent . Sterility erage sterility peratures . M9 ' s sterility increased greatly losses sometimes are two to three times this 4.5 to 49.7 percent between the Sacra - from level , however , depending on the variety , mento County and Davis ( early ) locations . In production area , and year . the same comparison , M - 101 only increased Cold night temperatures below 60 " F 10 to from 7.3 to 17.7 percent . Thus , M9 was much 14 days before heading are known to be one more susceptibleto cold than M - 101 , whereas of the major causes of sterility , and the rice - growing region subjected to cool marine air - M9 had less sterility than in moderate areas flow from the San Francisco Bay ( San Joa - M - 101 and the other varieties . quin , Sacramento , and Yolo counties ) has a L - 201 and S - 201 showed a fairly consistent reputation for high sterility . Other factors of increased sterility in colder areas . pattern also considered to be causes are hot temperatures at flowering time and high levels of nitrogen fertilization ( rates above 150 pounds per acre ) . Rice sterility Sterility has displayed high varietal as well as geographic variation . The purpose of this research was to analyzethe sterility perform - ances of four commercially important rice varietiesat widely different locationsto assess the variety - environment factors related to high sterility . In moderate areas , they had higher sterility M - 101 , M9 , S - 201 , and L - 201 , commercial than M9 , with L - 201 the highest of the three . varieties with early maturity , short stature , L - 201 and S - 201 In the colder Davis trials , and high yield , were selected for investiga - generally were intermediate between the low tion . Varieties were grown in a randomized M - 101 and high sterility of M9 . sterility of complete block design with four replications Comparison of sterility between locations 12 miles east of at the following locations : gives some insight into the effect of different Stockton in San Joaquin County ; 5 miles east environmental factors on sterility . Sterilityin of the Sacramento metropolitan airport in the Davis ( early ) test was significantlyhigher Sacramento County ; between Knights Land - than in all other locations . This supports the ing and Dunnigan in northern Yolo County ; current knowledge that cold temperatures do 5 miles north of Marysvillein Yuba County ; cause significant sterility . These conditions in Kern County near Bakersfield ; and at the probably occur rarely in most parts of the Davis Rice Research facility ( early and late rice - growing region , but when they do occur , 1 mile west of Davis , Yolo County . plantings ) , large increases in sterility can be expected . If one looks at the overall varietal means The data also show a significant difference ( table l ) , M - 101 had significantlyless sterility in sterility between locations in the moderate than the other three varieties . L - 201 was temperature area . Sacramento County had significantly higher in sterility than the other significantly less sterility than San Joaquin three varieties . S - 201 and M9 had similar , in - County . Yuba and Yolo ( north ) trials both termediate sterilitybetween M - 101 and L - 201 . had significantly higher blanking than the However , the varieties did not perform simi - San Joaquin and Sacramento tests . Sincethe larly at all locations . A significant variety x a moderate temperature four locations are in location interaction was demonstrated . area , the sterility differences must be due to M9 Analyzing the sterility performance of factor @ ) other than temperature extremes and M - 101 at the different locations explains ( either high or low ) . A possible factor to con - this interaction . Although M9 had higher sider is nitrogen fertilization rate . Our pre - M - 101 and S - 201 , M9 overall sterility than ( CariforniaAgriculture , Novem - vious work had the lowest sterility of all four varieties in ber - December 1980 ) has shown that sterility the moderate - temperature areas ( Yuba , significantly increased when nitrogen appli - northern Yolo , Sacramento , San Joaquin cation was higher than 120 pounds per acre . counties ) . Moderate areas are defined as of nitrogen We did not determinethe amount those in which air temperatures stayed above in the soil at planting time , nor were different 55 O F at meiosis ( 10 to 14 days before flower - rates of nitrogen applied . Therefore it was ing ) and below 95 O F at flowering ( see table impossible to obtain positive evidence that 2 ) . Cold areas are those where minimal tem - nitrogen fertilizer rates affected sterility . peratures at meiosis fall below 55 F ( the two However , it may be more than coincidental 6 CALIFORNIA AGRICULTURE , JANUARY - FEBRUARY 1982 that the two locations with the highest nitrogen rates ( Yuba and Yolo , north ) had TABLE 1 . Sterility comparisonsbetween varieties the highest sterility . at different locations in 1979 statewide trials 100O F at floweringtime Temperatureup to of cultivars ' Sterility does not appear to contribute significantlyto Location M - 101 5201 M9 L - 201 Mean sterility . Sterilitydata at the hot Kern County O h Ya YO YO YO trial were incomplete because of bird dam - SacramentoCounty 7.3 c 9.1 ef 4.5 f 9.9 d 7.7 d San JoaquinCounty 9.3 c 10.0 def 7.5 def 12.3 cd 9.8 c M9 and s - 201 were age . However , samplesof YoloCounty ( north ) 10.4 c 15.2 bcd 6.4 ef 19.4 b 12.9 b taken . Although maximal temperature dur - Davis ( late ) 12.3 bc 8.4 f 16.1 bc 15.8 bc 13.2 b ing flowering at this test was much higher Yuba County 16.4 ab 14.0 cde 11.0 cde 14.5 bcd 14.0 b ( over 100 " F ) than in any other area in the 17.7 a 31.3 a 49.7 a 41.3 a 35.0 a Davis ( early ) rice - growing region , sterility was low . Data 8.9 t 8.0 t Kern County Mean 12.2 c 14.7 b 15.9 b 18.9 a from sterility studies in the Imperial Valley ' Means not having the same letter in common are significantlydifferent at the . 05 level according to Duncan's ( author's unpublished data ) indicate that New Multiple RangeTest . Comparisonswere calculatedfor the same variety at differentlocations , differentover . some Californiavarietiesmaintain high floret all locationmeans , and different overall variety means . $ Not includedIn the means or the statistical analysis . fertility under hot conditions at flowering 76 and M7 had sterilitypercent - time . Calrose varies with area and variety James E . Board 0 Maurice L . Peterson ages of only 22.4 and 21.2 percent , respec - TABLE 2 . Headingand temperature data for varieties tested for tively , while lines reported to be heat tolerant sterility in 1979 statewide trials introduced from the tropics showed sterility Mean Mean ranging from 30 to 80 percent . min . max . In summary , the sterility data of M - 101 , Mean temp . temp . M9 , L - 201 and S - 201 in the 1979 statewide Seeding heading during eatringt trials demonstrate some important points Location Variety date date meiosis . flow about this phenomenon . Sterility markedly " F " F 51.1 5 / 7 / 79 8 / 22 M - 101 87.8 Davis ( early ) increases when rice is grown in areas where 53.8 87.3 911 M9 air temperatures fall below 55 " F during 917 53.6 93.3 L - 201 meiosis . However , significant sterility differ - 54.1 87.4 8 / 30 s - 201 ences can also occur betweenlocations within moderate areas . Hot temperatures at flower - 51.7 86.7 5118179 8119 Davis ( late ) M - 101 54.1 87.4 8130 M9 ing are an unlikely cause , since low sterility 52.9 89.0 913 L - 201 S - 201 and M9 when grown in the occurred in 52.4 87.2 8126 s - 201 hot Kern County locations . M - 101 showed the least sterility of all four 94.4 5115 / 79 8 / 10 59.2 M - 101 Yolo County 8114 93.3 56.3 M9 varietieswhen data were averaged over all lo - ( north ) 89.7 8124 55.0.5 L - 201 cations . However , an analysis of variety 90.2 54 8120 s - 201 means at specificlocations showsthat M9 ac - tually has less blanking in moderate areas , 92.6 64.3 M - 101 5115179 818 Yuba County M - 101 demonstrates lower sterility in but 91.6 63.8 8112 M9 86.2 61.8 8118 L - 201 colder areas . L - 201 had significantly higher 91.3 62.1 8 / 14 s - 201 overall sterilitythan the other three varieties . S - 201 was fairly stable , having less sterility 97.1 59.4 5 / 8 / 79 818 M . 101 SacramentoCounty L - 201 at all locations , but generally than 94.3 57.5 8111 M9 more than M9 and M - 101 . However , in colder 93.2 54.8 8 / 14 L - 201 93.2 54.8 8114 s - 201 areas S - 201 had less sterilitythan M9 . Results of these trials should be useful to ricegrowers 94.2 64.9 M - 101 5 / 14 / 79 8110 San Joaquin County when choosing varietiesfor different planting 88.4 62.6 8116 M9 dates and climatic areas . 90.2 61 . O L - 201 8125 91.4 60.7 8 / 22 s - 201 JamesE . Board , formerly Post GraduateResearch 100.2 76.0 5111 / 79 7 / 31 M9 - 201 Kern County Co / vornia , Davis , is Agronomist , University of 100.8 s 74.6 817 now Assistant Professor of Agronomy , Louisiana ' Mean minimaltemperatureaveragedover the period10 to 20 days before heading . 70803 . Maurice State University , Baton Rouge , LA Wean maximaltemperatureover a 10 - day period begining 5 days beforeheading . L . Peterson isProfessor , Emeritus , Deportment of Agronomy and Range Science , U.C . , Davis . CALIFORNIAAGRICULTURE , JANUARY - FEBRUARY1982 7