Climate change-induced heat stress combines two challenges:high day-and nighttime temperatures,and physiological water deficit due to demand-side drought caused by increase in vapor-pressure deficit.It is one of the m...Climate change-induced heat stress combines two challenges:high day-and nighttime temperatures,and physiological water deficit due to demand-side drought caused by increase in vapor-pressure deficit.It is one of the major factors in low productivity of maize in rainfed stress-prone environments in South Asia,affecting a large population of smallholder farmers who depend on maize for their sustenance and livelihoods.The International Maize and Wheat Improvement Center(CIMMYT)maize program in Asia,in partnership with public-sector maize research institutes and private-sector seed companies in South Asian countries,is implementing an intensive initiative for developing and deploying heat-tolerant maize that combines high yield potential with resilience to heat and drought stresses.With the integration of novel breeding tools and methods,including genomics-assisted breeding,doubled haploidy,fieldbased precision phenotyping,and trait-based selection,new maize germplasm with increased tolerance to heat stress is being developed for the South Asian tropics.Over a decade of concerted effort has resulted in the successful development and release of 20 high-yielding heat-tolerant maize hybrids in CIMMYT genetic backgrounds.Via public–private partnerships,eight hybrids are presently being deployed on over 50,000 ha in South Asian countries,including Bangladesh,Bhutan,India,Nepal,and Pakistan.展开更多
Information on the genetic relationship between tropical maize (Zea mays L), germplasm and temperate maize germplasm is of great value to maize breeding. The objective of this study was to determine the combining abil...Information on the genetic relationship between tropical maize (Zea mays L), germplasm and temperate maize germplasm is of great value to maize breeding. The objective of this study was to determine the combining ability and genetic relationship of 25 inbreds extracted from five tropical maize populations and a land race, with four temperate maize inbreds (Huangzaosi, Mol7, B73 and Dan 340). The 25 tropical inbreds were crossed with the four temperate inbreds and evaluated. Lines from Suwanl and POP28 had high general combining ability (GCA) for grain yield. The lines from POP32 (ETO) had the highest special combining ability (SCA) with B73; the average SCA value of the 5 lines was 879 kg/ha. The lines from Suwanl had the second-highest SCA (584 kg/ha) with Huangzaosi. The lines from Suwanl had the greatest relative heterosis (20%) with B73, followed by the lines from POP32 (ETO) with B73 (19%). Five heterotic patterns have been identified from this study: Suwanl × Reid, ETO × Reid, POP28× Reid, POP28× Ludahong-gu, and Suwan1× Lancaster.展开更多
Reid, Lancaster, Tuxpeno and Suwan are the most common maize (Zea mays L.) germplasms. Reid × Lancaster and Suwan × Tuxpeno are very important heterotic patterns in temperate areas and tropical areas, respec...Reid, Lancaster, Tuxpeno and Suwan are the most common maize (Zea mays L.) germplasms. Reid × Lancaster and Suwan × Tuxpeno are very important heterotic patterns in temperate areas and tropical areas, respectively. Broadening the genetic basis of maize has usually been conducted in inter-populations formed by crossing temperate and tropical germplasms. Reciprocal recurrent selection (RRS) is a breeding procedure to improve the inter-populational cross of two base populations. The objective of this study was to evaluate the direct and indirect effects of reciprocal recurrent selection on grain yield in the TR (Tuxpeno-Reid) and SL (Suwan-Lancaster) maize populations. The populations and the inter-populational crosses of each selection cycle, as well as two commercial hybrids, were evaluated in four environments. The effect of mean grain yield on TR × SL inter-population crosses was 4.63% (or 0.365 Mg·ha-1) cycle-1. The grain yield of SL increased by 2.78% (or 0.20 Mg·ha-1) cycle-1, but the grain yield of TR essentially did not change. Most changes in other agronomic traits occurred in the desired direction. After 3 selection cycles, the ear tip-barrenness length decreased in TR × SL, TR and SL by 39.70%, 37.50% and 24.57%, respectively, which indicates that the increase in grain yield may be largely due to a decreasing ear tip-barrenness length. The mid-parent heterosis of grain yield of the inter-populational cross increased from 15.49% to 25.96% from C0 to C3. The mean grain yields of TRC3 × SLC3 were 100.01% and 103.88% of the mean grain yields of the commercial single-crosses GD8 and QD16, respectively. The results suggest that Tuxpeno-Reid × Suwan-Lancaster may be possible new heterotic patterns in the southern region of China.展开更多
Maize is one of the most important cereal crops in Sub-Saharan Africa and an important source of energy for humans. However, the difference in the dedifferentiation frequency of immature embryos among various genotype...Maize is one of the most important cereal crops in Sub-Saharan Africa and an important source of energy for humans. However, the difference in the dedifferentiation frequency of immature embryos among various genotypes indicates that callus induction and genetic transformation is dependent on the genotype. This phenomenon is an impediment in the fundamental process of improving tropical maize germplasm especially through genetic engineering. Here, five tropical maize （Zea mays L.） genotypes, CML 216, CML 144, A 04, E 04 and TL 21, were evaluated for callus induction on MS medium supplemented with the growth regulator dicamba. Embryogenic and non embryogenic callus induction was independent ofgenotype when young immature embryos, 12 days after pollination （DAP） were used for tissue culture in combination with dicamba. The optimal concentration of dicamba for induction ofembryogenic callus in all the genotypes was 3 mg/L, which was also the concentration at which non embryogenic callus formation was lowest. The frequency of embryogenic callus induction ranged from 35% to 79% among the five genotypes and somatic embryos regenerated R0 shoots that produced normal R1 progenies. This regeneration method is expected to facilitate the development of a more efficient genotype independent Agrobacterium- mediated transformation system for tropical inbred lines.展开更多
Yellow maize contains high levels of β-carotene(βC), making it an important crop for combating vitamin A deficiency through biofortification. In this study, nine maize inbred lines were selected at random from 31 pr...Yellow maize contains high levels of β-carotene(βC), making it an important crop for combating vitamin A deficiency through biofortification. In this study, nine maize inbred lines were selected at random from 31 provitamin A(PVA) maize inbred lines and crossed in a partial diallel mating design to develop 36 crosses. The crosses were evaluated in the field in two locations(Samaru and Kerawa) and their seed carotenoid content were determined by high-performance liquid chromatography. The modes of gene action, heritability, and correlations between agronomic traits and carotenoid content were estimated. Additive genetic variances(σ~2a) were lower than non-additive genetic variances(σ~2d) for all the carotenoids, plant height(PH), and grain yield(GY), suggesting a preponderance of non-additive gene action. Broad-sense heritability(H^2) was high(H^2> 60%) for zeaxanthin,days to anthesis, and PH, moderate(30% < H^2< 60%) for lutein and GY, and low(H^2< 30%)for alpha carotene, beta cryptoxanthin, βC, and PVA. Genetic advance as a percentage of mean, considered with H^2, also suggests a preponderance of non-additive gene action for PVA carotenoids. Hybrid variety development is thus an appropriate approach to improving grain yield and PVA. GY showed no significant genotypic correlations with carotenoid content, suggesting that these traits can be improved concurrently. Thus, there is ample scope for improvement of PVA and GY in the sample of tropical-adapted maize.展开更多
This paper presents the effects of alternative nitrogen management regimes on production of Eucalyptus in tropics and sub-tropics carried out in autumn, 2011. The aim of the study was to review alternative nitrogen ma...This paper presents the effects of alternative nitrogen management regimes on production of Eucalyptus in tropics and sub-tropics carried out in autumn, 2011. The aim of the study was to review alternative nitrogen management regimes that could enhance the positive effects and reduce negative effects of different Eucalyptus species in the perspective of smallholders. Literature review was used to survey the alternative nitrogen management regimes on eucalyptus trees. There was a significant improvement （P ≤ 0.01） in mean annual increment （MAI） as measured at seven years of Eucalyptus tereticornis in the plots planted with only legume, pueraria and stylosanthes, compared to that of the control on altitude 150 m and rainfall of 2,000 mm at the age of seven years, The MAI of Eucalyptus urophylla and Eucalyptus camaldulensis in plots planted with beans and rice shows a significant improvement （P ≤ 0.05） over the control treatment. Only the plots treated with nitrogen fertilizer 550 kg/ha showed significant improvement （P ≤ 0.05） in terms of MAI of Eucalyptus nitens, compared to the control treatment. In general, it can be concluded that as these alternative management regimes enhance productivity of Eucalyptus woodlots, the challenge for the small-scale farmers is on how to manage them sustainably. Therefore, forest policies that take consideration of increasing production of Eucalyptus and managing biodiversity with reference to these alternative management regimes should be developed in tropics and sub-tropics.展开更多
基金the support of USAID under the Feed the Future Initiative of the U.S.government through the project Heat Tolerant Maize for Asia(Grant No.:CGIAR Trust Fund MTO No.069033)/CIMMYT)Financial support received earlier from the CGIAR Research Program MAIZEthe CGIAR Initiatives on Accelerated Breeding and SeEdQUAL。
文摘Climate change-induced heat stress combines two challenges:high day-and nighttime temperatures,and physiological water deficit due to demand-side drought caused by increase in vapor-pressure deficit.It is one of the major factors in low productivity of maize in rainfed stress-prone environments in South Asia,affecting a large population of smallholder farmers who depend on maize for their sustenance and livelihoods.The International Maize and Wheat Improvement Center(CIMMYT)maize program in Asia,in partnership with public-sector maize research institutes and private-sector seed companies in South Asian countries,is implementing an intensive initiative for developing and deploying heat-tolerant maize that combines high yield potential with resilience to heat and drought stresses.With the integration of novel breeding tools and methods,including genomics-assisted breeding,doubled haploidy,fieldbased precision phenotyping,and trait-based selection,new maize germplasm with increased tolerance to heat stress is being developed for the South Asian tropics.Over a decade of concerted effort has resulted in the successful development and release of 20 high-yielding heat-tolerant maize hybrids in CIMMYT genetic backgrounds.Via public–private partnerships,eight hybrids are presently being deployed on over 50,000 ha in South Asian countries,including Bangladesh,Bhutan,India,Nepal,and Pakistan.
基金funded by the Natural Science Foundation of Yunnan Province(980006Z).
文摘Information on the genetic relationship between tropical maize (Zea mays L), germplasm and temperate maize germplasm is of great value to maize breeding. The objective of this study was to determine the combining ability and genetic relationship of 25 inbreds extracted from five tropical maize populations and a land race, with four temperate maize inbreds (Huangzaosi, Mol7, B73 and Dan 340). The 25 tropical inbreds were crossed with the four temperate inbreds and evaluated. Lines from Suwanl and POP28 had high general combining ability (GCA) for grain yield. The lines from POP32 (ETO) had the highest special combining ability (SCA) with B73; the average SCA value of the 5 lines was 879 kg/ha. The lines from Suwanl had the second-highest SCA (584 kg/ha) with Huangzaosi. The lines from Suwanl had the greatest relative heterosis (20%) with B73, followed by the lines from POP32 (ETO) with B73 (19%). Five heterotic patterns have been identified from this study: Suwanl × Reid, ETO × Reid, POP28× Reid, POP28× Ludahong-gu, and Suwan1× Lancaster.
文摘Reid, Lancaster, Tuxpeno and Suwan are the most common maize (Zea mays L.) germplasms. Reid × Lancaster and Suwan × Tuxpeno are very important heterotic patterns in temperate areas and tropical areas, respectively. Broadening the genetic basis of maize has usually been conducted in inter-populations formed by crossing temperate and tropical germplasms. Reciprocal recurrent selection (RRS) is a breeding procedure to improve the inter-populational cross of two base populations. The objective of this study was to evaluate the direct and indirect effects of reciprocal recurrent selection on grain yield in the TR (Tuxpeno-Reid) and SL (Suwan-Lancaster) maize populations. The populations and the inter-populational crosses of each selection cycle, as well as two commercial hybrids, were evaluated in four environments. The effect of mean grain yield on TR × SL inter-population crosses was 4.63% (or 0.365 Mg·ha-1) cycle-1. The grain yield of SL increased by 2.78% (or 0.20 Mg·ha-1) cycle-1, but the grain yield of TR essentially did not change. Most changes in other agronomic traits occurred in the desired direction. After 3 selection cycles, the ear tip-barrenness length decreased in TR × SL, TR and SL by 39.70%, 37.50% and 24.57%, respectively, which indicates that the increase in grain yield may be largely due to a decreasing ear tip-barrenness length. The mid-parent heterosis of grain yield of the inter-populational cross increased from 15.49% to 25.96% from C0 to C3. The mean grain yields of TRC3 × SLC3 were 100.01% and 103.88% of the mean grain yields of the commercial single-crosses GD8 and QD16, respectively. The results suggest that Tuxpeno-Reid × Suwan-Lancaster may be possible new heterotic patterns in the southern region of China.
文摘Maize is one of the most important cereal crops in Sub-Saharan Africa and an important source of energy for humans. However, the difference in the dedifferentiation frequency of immature embryos among various genotypes indicates that callus induction and genetic transformation is dependent on the genotype. This phenomenon is an impediment in the fundamental process of improving tropical maize germplasm especially through genetic engineering. Here, five tropical maize （Zea mays L.） genotypes, CML 216, CML 144, A 04, E 04 and TL 21, were evaluated for callus induction on MS medium supplemented with the growth regulator dicamba. Embryogenic and non embryogenic callus induction was independent ofgenotype when young immature embryos, 12 days after pollination （DAP） were used for tissue culture in combination with dicamba. The optimal concentration of dicamba for induction ofembryogenic callus in all the genotypes was 3 mg/L, which was also the concentration at which non embryogenic callus formation was lowest. The frequency of embryogenic callus induction ranged from 35% to 79% among the five genotypes and somatic embryos regenerated R0 shoots that produced normal R1 progenies. This regeneration method is expected to facilitate the development of a more efficient genotype independent Agrobacterium- mediated transformation system for tropical inbred lines.
基金the Institutefor Agricultural Research, Ahmadu Bello University (IAR/ABU) Samaru, Nigeria, for the funding support provided for this study
文摘Yellow maize contains high levels of β-carotene(βC), making it an important crop for combating vitamin A deficiency through biofortification. In this study, nine maize inbred lines were selected at random from 31 provitamin A(PVA) maize inbred lines and crossed in a partial diallel mating design to develop 36 crosses. The crosses were evaluated in the field in two locations(Samaru and Kerawa) and their seed carotenoid content were determined by high-performance liquid chromatography. The modes of gene action, heritability, and correlations between agronomic traits and carotenoid content were estimated. Additive genetic variances(σ~2a) were lower than non-additive genetic variances(σ~2d) for all the carotenoids, plant height(PH), and grain yield(GY), suggesting a preponderance of non-additive gene action. Broad-sense heritability(H^2) was high(H^2> 60%) for zeaxanthin,days to anthesis, and PH, moderate(30% < H^2< 60%) for lutein and GY, and low(H^2< 30%)for alpha carotene, beta cryptoxanthin, βC, and PVA. Genetic advance as a percentage of mean, considered with H^2, also suggests a preponderance of non-additive gene action for PVA carotenoids. Hybrid variety development is thus an appropriate approach to improving grain yield and PVA. GY showed no significant genotypic correlations with carotenoid content, suggesting that these traits can be improved concurrently. Thus, there is ample scope for improvement of PVA and GY in the sample of tropical-adapted maize.
文摘This paper presents the effects of alternative nitrogen management regimes on production of Eucalyptus in tropics and sub-tropics carried out in autumn, 2011. The aim of the study was to review alternative nitrogen management regimes that could enhance the positive effects and reduce negative effects of different Eucalyptus species in the perspective of smallholders. Literature review was used to survey the alternative nitrogen management regimes on eucalyptus trees. There was a significant improvement （P ≤ 0.01） in mean annual increment （MAI） as measured at seven years of Eucalyptus tereticornis in the plots planted with only legume, pueraria and stylosanthes, compared to that of the control on altitude 150 m and rainfall of 2,000 mm at the age of seven years, The MAI of Eucalyptus urophylla and Eucalyptus camaldulensis in plots planted with beans and rice shows a significant improvement （P ≤ 0.05） over the control treatment. Only the plots treated with nitrogen fertilizer 550 kg/ha showed significant improvement （P ≤ 0.05） in terms of MAI of Eucalyptus nitens, compared to the control treatment. In general, it can be concluded that as these alternative management regimes enhance productivity of Eucalyptus woodlots, the challenge for the small-scale farmers is on how to manage them sustainably. Therefore, forest policies that take consideration of increasing production of Eucalyptus and managing biodiversity with reference to these alternative management regimes should be developed in tropics and sub-tropics.
