Genotype x enviroment interaction for quality parameters of irrigated spring wheat

[摘要] English: The primary aim of this study was to examine the effect of environment, genotype and their interaction onbread-making quality characteristics of irrigated spring wheat cultivars. The wheat samples were obtainedfrom trials conducted in irrigation areas by the Small Grain Institute (Breeding Department), during 1997 and1998. The trials were conducted at six localities in 1997 and seven in 1998. Among the localities five were incooler and two in warmer irrigation areas. For the cultivars nine were common in both years but two wereadded in 1997, and one in 1998 making a total of 11 and 10 respectively. The source of cultivars was SmallGrain Institute (5) and Sensako (7). Trials were conducted at experimental stations or farms of collaboratorswhere the soil and climate are representative of a specific area. A randomised block design with fourreplications was used. Interrow spacing was maintained at 0.17 m and planting rate varied according to 1000kernel mass of a specific cultivar. This was to ensure that a uniform stand of plants per m-2 is achieved.Fertilizers were applied according to recommendations on the basis of individual soil analyses. Othermanagement practices were performed as required and a net plot of six rows (5.1 m-2) was harvested. Thesamples were analysed for a total of 21 quality characteristics, important for bread-making.The statistical analysis of the results showed that both genotype, environment and their interaction hadsignificant influence on quality characteristics. This implied presence of variations among genotypes,environmental conditions as well as interaction effects in their response to quality parameters. However,above all, environment was the most dominant factor, which contributed to the variation for' most of thecharacteristics. Protein content (particularly flour) closer to 12% (optimum) and with good quality was veryimportant. This character together with higher grain filling to ensure optimum starch-protein interaction werenecessary for cultivars, sites and interaction effects to show good quality characteristics. Generally climaticconditions particularly temperature showed interference with quality parameters especially in warmer areas.This is due to the fact that high temperature has an influence on protein composition and definitely the ratiosof glutenin-ta-gliadin part of the protein. However, for cooler areas, the protein quality was probably notaffected, but the higher grain filling realised at some of the sites caused protein content to be low. This isagain due to the fact that in high potential environments, nitrogen (N) is first utilised for maximum plantgrowth and yield. Thereafter the excess N is then translocated to the grain for storage as protein. Consideringthe quality parameters themselves, some showed negative correlations with others. This indicates thatimprovement of one characteristic will have a negative influence on the other, and this is the cause ofbreeders delay in releasing new cultivars. By using the canonical variate analysis (cómponent of AMMI), itwas possible to see which characteristics group together in discriminating among genotypes, locations and interaction effects. Therefore with this analysis it was possible to determine which characters needappropriate genotype, environment or interaction effects to get optimum values.From the study results we can recommend that, T4, which ranked lower for most of the quality parametersmay be risky for very large commercial production. However, this genotype may be used as a donor parentfor improvement of alveograph P/L ratio for which it showed good results. Other genotypes, which alsoshowed less potential, include, SST65, SSTSS, SST876 and Palmiet. These genotypes should be grownunder conditions where they are expected to perform well. An example is Palmiet at Loskop, Koedoeskopand BullHill where it showed positive environment interactions for loaf volume at 12% protein. Also withenvironment protein yield closer to optimum (not very low), Palmiet may perform intermediately for most ofthe parameters. SST55 and SST65 showed higher loaf volumes at 12% protein and may be used to improvethis parameter. Nevertheless they were lower in other parameters particularly mixograph development time,mixograph point score and SDS-sedimentation. Kariega ranked lower for alveograph P/L ratio in both yearsand may need improvement for this parameter. However, this genotype together with SST38, SST57,SST822, SST825, Inia and Marico showed intermediate to higher rank for most of the characteristics.Therefore they may be reliable at most of the sites unless environment becomes less optimal or negativeenvironment interactions occur.For the locations, Loskop was the site that showed the most contrast with other sites. This is due to the factthat this site had values for mixograph development time, and to a lesser extent mixograph point score aboverecommended values for both years. Also the high protein realised at this site implies management practicesshould be aimed at reducing fertility and thus nitrogen yield. Therefore at Loskop, Koedoeskop (warmerareas) and Barkly West, cultivar selection and timing of seeding are necessary to ensure that grain filling isnot influenced or does not coincide with higher temperatures. The higher hectoliter and kernel masses atmost of the sites except Loskop implies higher grain yields and this was the main cause of realised lowprotein content. Therefore for other sites in addition to cultivar selection, management practices to increasefertility and thus protein content are necessary particularly at Prieska. Also since leaching may lose fertility,there is a need to control the irrigation water. Genotype x environment interactions were observed for proteincontent and related parameters. Grain filling was also responsible for this interaction particularly for theparameters influenced by starch-protein interaction. However, Prieska, and to a lesser extent Douglasshowed less environment interactions compared to other sites. Therefore at Loskop, Koedoeskop, Hopetown,BullHilI and Barkly West identification of genotypes with positive environment interactions will be necessary.The canonical variate analyses for genotypes showed that 10 parameters were mainly responsible for thevariations among genotypes. Mixograph development time, mixograph point score, alveograph P/L ratio,alveograph strength, loaf volume at 12% protein, SDS-sedimentation, breakflour yield, kernel mass (TKM and SKCS-W) and SKCS-diameter were responsible for genotype variation. Therefore for all theseparameters, identification of cultivars, which will give desirable values, is important. Breeders may give thempriority when making selection in their programmes. The canonical variate analysis for environments showedmore parameters, about 13 being influenced by the environment variations. However, most of them wereassociated with protein content and grain filling. Most of the characteristics, which discriminated theinteraction effects, were those under genotype and environment. Therefore identification of cultivars, whichwill give good results, and management to ensure higher protein with good quality and higher grain filling, arenecessary. Taking into account the grading of wheat Prieska and Douglas showed to be stable and may givea BSS grade for most of the cultivars. BuIIHilI, Hopetown, Barkly West and Koedoeskop had intermediatestability and gave BS1 and BS2 grade for most of the cultivars particularly in 1998 due to low protein content.Loskop was alone showing to be highly unstable as it gave BS2 in 1997 for all cultivars, and in 1998 theywere BPS and BP1. However, for this site despite the grade being higher, quality characteristics may showlow values. Therefore cultivar selection and management are important to ensure that the grades aremaintained and quality characteristics to be closer to optimum. Also mixing the products, particularly fromLoskop and to a lesser extent BuIIHilI, Barkly West, Hopetown and Koedoeskop when the environments arenot optimal with those of Prieska and Douglas will improve the quality. The probable cultivars to be mixed areSST825, Inia, SST822, SST57, SST38 and to a lesser extent Marico and Kariega. Therefore there is a needfor processing industries and particularly researchers and farmers to work closer together. This will help toidentify which cultivars and management practices need to be implemented at certain locations in order tohave good quality crops. Also, since farmers are risk takers, despite following all the recommendations,environmental deviation may cause their products to have reduced/poor quality. In such a case, thegovernment and processing industries should have a programme of supporting such farmers.

[发布机构] University of the Free State