Person: Grudloyma, P.
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Grudloyma
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Grudloyma, P.
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- Use of genomic estimated breeding values results in rapid genetic gains for drought tolerance in maize(Crop Science Society of America, 2017) Vivek, B.; Krishna, G.; Vengadessan, V.; Babu, R.; Zaidi, P.; Kha, L.Q.; Mandal, S.S.; Grudloyma, P.; Takalkar, S.; Krothapalli, K.; Singh, I.S.; Ocampo, E.T.M.; Fan, X.M.; Burgueño, J.; Azrai, M.; Singh, R.P.; Crossa, J.More than 80% of the 19 million ha of maize (Zea mays L.) in tropical Asia is rainfed and prone to drought. The breeding methods for improving drought tolerance (DT), including genomic selection (GS), are geared to increase the frequency of favorable alleles. Two biparental populations (CIMMYT Asia Population 1 [CAP1] and CAP2) were generated by crossing elite Asian-adapted yellow inbreds (CML470 and VL1012767) with an African white drought-tolerant line, CML444. Marker effects of polymorphic single-nucleotide polymorphisms (SNPs) were determined from testcross (TC) performance of F2:3 families under drought and optimal conditions. Cycle 1 (C1) was formed by recombining the top 10% of the F2:3 families based on TC data. Subsequently, (i) C2[PerSe_PS] was derived by recombining those C1 plants that exhibited superior per se phenotypes (phenotype-only selection), and (ii) C2[TC-GS] was derived by recombining a second set of C1 plants with high genomic estimated breeding values (GEBVs) derived from TC phenotypes of F2:3 families (marker-only selection). All the generations and their top crosses to testers were evaluated under drought and optimal conditions. Per se grain yields (GYs) of C2[PerSe_PS] and that of C2[TC-GS] were 23 to 39 and 31 to 53% better, respectively, than that of the corresponding F2 population. The C2[TC-GS] populations showed superiority of 10 to 20% over C2[PerSe-PS] of respective populations. Top crosses of C2[TC-GS] showed 4 to 43% superiority of GY over that of C2[PerSe_PS] of respective populations. Thus, GEBV-enabled selection of superior phenotypes (without the target stress) resulted in rapid genetic gains for DT.
Publication - Identification of drought, heat, and combined drought and heat tolerant donors in maize(Crop Science Society of America (CSSA), 2013) Cairns, J.E.; Crossa, J.; Zaidi, P.; Grudloyma, P.; Sanchez, C.; Araus, J.L.; Thaitad, S.; Makumbi, D.; Magorokosho, C.; Banziger, M.; Menkir, A.; Hearne, S.; Atlin, G.Low maize (Zea maysL.) yields and the impacts of climate change on maize production highlight the need to improve yields in eastern and southern Africa. Climate projections suggest higher temperatures within drought-prone areas. Research in model species suggests that tolerance to combined drought and heat stress is genetically distinct from tolerance to either stress alone, but this has not been confirmed in maize. In this study we evaluated 300 maize inbred lines testcrossed to CML539. Experiments were conducted under optimal conditions, reproductive stage drought stress, heat stress, and combined drought and heat stress. Lines with high levels of tolerance to drought and combined drought and heat stress were identified. Significant genotype × trial interaction and very large plot residuals were observed; consequently, the repeatability of individual managed stress trials was low. Tolerance to combined drought and heat stress in maize was genetically distinct from tolerance to individual stresses, and tolerance to either stress alone did not confer tolerance to combined drought and heat stress. This finding has major implications for maize drought breeding. Many current drought donors and key inbreds used in widely grown African hybrids were susceptible to drought stress at elevated temperatures. Several donors tolerant to drought and combined drought and heat stress, notably La Posta Sequia C7-F64-2-6-2-2 and DTPYC9-F46-1-2-1-2, need to be incorporated into maize breeding pipelines.
Publication - Effectiveness of Genomic Prediction of Maize Hybrid Performance in Different Breeding Populations and Environments(Genetics Society of America, 2012) Windhausen, V.S.; Atlin, G.; Hickey, J.; Crossa, J.; Jannink, J.L.; Sorrells, M.E.; Babu, R.; Cairns, J.E.; Tarekegne, A.T.; Semagn, K.; Beyene, Y.; Grudloyma, P.; Technow, F.; Riedelsheimer, C.; Melchinger, A.E.Genomic prediction is expected to considerably increase genetic gains by increasing selection intensity and accelerating the breeding cycle. In this study, marker effects estimated in 255 diverse maize (Zea mays L.) hybrids were used to predict grain yield, anthesis date, and anthesis-silking interval within the diversity panel and testcross progenies of 30 F2-derived lines from each of five populations. Although up to 25% of the genetic variance could be explained by cross validation within the diversity panel, the prediction of testcross performance of F2-derived lines using marker effects estimated in the diversity panel was on average zero. Hybrids in the diversity panel could be grouped into eight breeding populations differing in mean performance. When performance was predicted separately for each breeding population on the basis of marker effects estimated in the other populations, predictive ability was low (i.e., 0.12 for grain yield). These results suggest that prediction resulted mostly from differences in mean performance of the breeding populations and less from the relationship between the training and validation sets or linkage disequilibrium with causal variants underlying the predicted traits. Potential uses for genomic prediction in maize hybrid breeding are discussed emphasizing the need of (1) a clear definition of the breeding scenario in which genomic prediction should be applied (i.e., prediction among or within populations), (2) a detailed analysis of the population structure before performing cross validation, and (3) larger training sets with strong genetic relationship to the validation set.
Publication - Maize in Thailand: production systems, constraints, and research priorities(CIMMYT, 2004) Ekasingh, B.; Gypmantasiri, P.; Thong Ngam, K.; Grudloyma, P.This is one of a series of seven in-depth country studies on maize production systems in Asia, funded by the International Maize and Wheat Improvement Center (CIMMYT) and the International Fund for Agricultural Development (IFAD). It is part of a project designed to promote sustainable intensification of maize production systems while ensuring equitable income growth and improved food security, especially for poor households that depend on maize. Maize is one of five major crops grown in the uplands of Thailand, along with rice, cassava, sugar cane, and rubber trees. Government-promoted crop diversification, increased population growth, improved transportation networks, international trade, expansion of upland farming areas, and increased demand for grains from the domestic livestock and poultry industry stimulated Thailand’s maize production beginning in the 1980s. However, Thailand’s domestic maize supply is currently not sufficient to meet the needs of its in-country demands, and small quantities have to be imported. Rapid economic growth and accelerated urbanization are expected to create an even higher demand for maize in Thailand. This trend will lead to the intensification of current maize production systems, with more land being shifted to maize production, particularly in marginal areas. Thailand’s challenge is to produce more maize for an expanding market, while preserving the natural resource base and the environment through careful agricultural planning. Effective policy design and implementation must be based on comprehensive, accurate data on the current state of maize-based farming systems. This study characterized the social and biophysical maize production environment of Thailand; examined its response to increasing maize demand; determined constraints to future productivity growth; indicated the potential environmental consequences, and examined the options available for promoting sustainable growth in maize production.
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