Late Maturing Hybrids Research Articles

GGE biplot analysis and selection indices for yield and stability assessment of maize (Zea mays L.) genotypes under drought and irrigated conditions

Maize is mainly a rainfed crop prone to drought stress, suffering yield losses. The present study evaluated eleven early and nine late maturity hybrids to identify widely adapted genotypes under drought stress and irrigated conditions at the flowering stage. Genotypes showed 25.2% yield reduction under drought over irrigated conditions. GGE biplot analysis demonstrated major effect of environment (72–85%) on grain yield followed by genotype × environment (8–18%), identifying two different mega-environments under drought stress. Suitable selection indices identified DRMH 1417, DKC 7074 in the early and CMH12-686 in late maturity group as high-yielding and drought-tolerant hybrids.

Widely Targeted Metabolomic Analysis Provides New Insights into the Effect of Rootstocks on Citrus Fruit Quality.

The use of different rootstocks has a significant effect on the content of flavor components and overall fruit quality. However, little information is available about the metabolic basis of the nutritional value of citrus plants. In this study, UPLC-MS/MS (ultra-performance liquid chromatography-tandem mass spectrometry) was performed to analyze the metabolites of three late-maturing hybrid mandarin varieties ('Gold Nugget', 'Tango' and 'Orah') grafted on four rootstocks ('Trifoliate orange', 'Carrizo citrange', 'Red tangerine' and 'Ziyang Xiangcheng'). A total of 1006 metabolites were identified through OPLS-DA (Orthogonal Partial Least Squares-Discriminant Analysis) analysis. KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis revealed the most critical pathways among the different pathways associated with genes grafted on the four rootstocks that were differentially activated, including tryptophan metabolism and sphingolipid metabolism in 'Gold Nugget'; tryptophan metabolism, phenylpropanoid biosynthesis and sphingolipid metabolism in 'Tango'; and pantothenate and CoA biosynthesis- and photosynthesis-related biosynthesis in 'Orah'. A considerable difference between the different rootstocks was also observed in the accumulation of lipids, phenolic acids and flavonoids; further analysis revealed that the rootstocks regulated specific metabolites, including deacetylnomylinic acid, sudachinoid A, amoenin evodol, rutaevin, cyclo (phenylalanine-glutamic acid), cyclo (proline-phenylalanine), 2-hydroxyisocaproic acid, and 2-hydroxy-3-phenylpropanoic acid. The results of this study provide a useful foundation for further investigation of rootstock selection for late-maturation hybrid mandarin varieties.

Influence of Sowing Time on Fusarium and Fumonisin Contamination of Maize Grains and Yield Component Traits

The main aim of this research was to study the effect of two sowing times (early and late) on Fusarium and fumonisin contamination and some yield component traits of two maize hybrids from the FAO maturity groups 500 (ZP 560) and 600 (ZP 666) within a two-year growing season (2016–2017). F. verticillioides and F. subglutinans have been identified as Fusarium ear rot (FER) pathogens and potential producers of B-type fumonisins (FBs), with F. verticillioides as the predominant Fusarium species in both years. The incidence of F. verticillioides and FB levels were affected by sowing time and maize hybridity. With early sowing and the mid-maturity hybrid ZP 560, F. verticillioides and FB contamination were lower than with late sowing and the late-maturity hybrid ZP 666. Yield parameters also differed significantly between sowing time and maize hybrid treatments. Early sowing increased ear length (EL), number of grains per ear (NGE), grain weight per ear (GWE), and grain yield per hectare (GY). The late-maturity hybrid ZP 666 had higher yield component traits and GY than the mid-maturity hybrid ZP 560. EL, GWE, thousand-grain weight (TGW), and GY were affected by year. Interactions between sowing times and maize hybrids were highly significant (p ≤ 0.01) for FB level, GWE, and GY. The obtained results indicate the importance of applying early sowing to achieve high maize grain yields with lower contamination by F. verticillioides and FBs. Although mid-maturity hybrid ZP 560 and late-maturity hybrid ZP 666 showed significant differences in terms of levels of F. verticillioides and FB contamination, both were susceptible to F. verticillioides, with high FB levels. These results should be useful to breeders of maize hybrids to create genotypes more resistant to these fungal contaminants.

Evaluation of late maturity maize (Zea mays) hybrids under varying plant density and nutrient levels

Productivity of maize is influenced by selection of hybrids or improved varieties, plant population, nutrient management practices etc. These technological interventions may vary across locations. Therefore, two-year investigation was conducted during Rabi, 2019-21 at Department of Millets, Tamil Nadu Agricultural University, Coimbatore, India to evaluate the performance of late maturity maize hybrids under varying plant density and nutrient levels. The experiments were laid out in a split-split plot design replicated thrice. In the main plot, two plant densities viz., 60×25 cm and 60×20 cm spacing and in the sub plot, three nutrient levels viz., 100% RDF (250:75:75 NPK kg/ha), 90% RDF (225:68:68 NPK kg/ha) and STCR-IPNS (131:38:38 NPK kg/ha) and in the sub-sub plot, four late maturity maize hybrids viz., CMH12-686, CMH15-005, COH (M) 6 and NK6240 were tried. Based on the results of two years of experimentation, it is concluded that among the late maturity maize hybrids, CMH15-005 and CMH12-686 were found to be the most promising hybrids under a spacing of 60×20 cm with application of 100% recommended dose of fertilizer @250:75:75 NPK kg/ha. In future, these late maturity hybrids should be grown with the recommended spacing and nutrient level to achieve desirable productivity in maize.

Sowing methods of maise for hay in the forest-steppe zone of Western Siberia

The authors showed the results of studies of productivity parameters of different early maturing maise hybrids depending on the method of sowing. Experiment included 5 variants: single- seeded hybrids Kubansky 101 and Kubansky 500, Kubansky 101 + Kubansky 500 (50 + 50% of the full seeding rate), Kubansky 101 + Kubansky 500 (25 + 75%) and Kubansky 101 + Kubansky 500 (75 + 25%). The authors carried out a biological yield survey on 10 September. This recording showed that the ultra-early-ripening hybrid Kubansky 101 CB was in the phase of milk-wax maturity of the grain, and the late-ripening Kubansky 500 CB was in the phase of cob formation. In single-species crops, the yields were naturally higher. The late-maturing hybrid yielded 82.0 t/ha, 38.1 t/ha higher than the ultra-maturing hybrid. However, the dry matter yield of the second hybrid was 15.9 % higher, and the cob yield was 29 % higher. The dry matter concentration of the hybrid Kubansky 500 was only 18.8 %. The hybrid Kubansky 101 CB had a dry matter concentration of 34.7 %. Different variations with the ratio of hybrids of different ripeness groups in the sowing showed that in green matter yield, the variants where the proportion of late-ripening hybrid is higher are superior. Thus, the presence of 75% hybrid Kubansky 500 CB allowed obtaining the highest yield of 77.2 t/ha. This yield is almost two times higher than the yield of the single-variety ultra-ripening hybrid (43.9 t/ha). However, the dry matter concentration here was 20.2 %. According to the biochemical analysis of the silage batches harvested, all the forages were benign. No oily acid was detected, and lactic acid predominated over acetic acid. Hay prepared from hybrid Kubansky 101 SV was 33.8% in dry matter content, which compares favourably with silage prepared from hybrid Kubansky 500 SV and mixtures with Kubansky 101 SV. The hybrid Kubansky 500 SV and mixtures with Kubansky 101 SV accounted for 21 % dry matter content. In silage prepared from hybrid Kubansky 101 SV, the percentage of dry matter is 24.2-25 %.

Features and properties of tangerine hybrids derived from distant hybridization (Citrus var. unshiu×Poncirus trifoliata)

Among citrus crops in the subtropical zone of the of the Russian Federation Black Sea coast of Krasnodar Territory, only tangerines can be grown (Citrus reticulata Blanco var. unshiu Tan.). The expansion of planting is hindered by poor winter hardiness, that’s why breeders are faced with a task of creating new forms of mandarin that are maximally adapted to the extreme climatic conditions of the region. By using of a distant hybridisation it is possible to create such forms. Purposeful distant hybridization allows transferring the properties of one genus to another, which is leading to phenotypic and genotypic changes in hybrid generation. The article emphasizes the importance of distant hybridization. For the period 1995-2019, distant, recurrent and inter-hybrid hybridizations were carried out to create a new hybrid fund. The results of 19 combinations of crossing by using Poncirus trifoliata Raf., and hybrids which were obtained with the participation of this genus, as well as hybrid species: C.×insitorum, C.×citrangeqwa and the genus Fortunella Sw. Expanded forms were selected for further breeding with an early term of fruit ripening (I decade of October): YuМR-97; YuКR-22; ККR-27; ККR-22; МRКR-97-25; МRКR-97-25-1; КRМR-25-97, with later ripening (II decade of October: КVI-1, КVI-3, YuI-12 received with C. insitorum. Also with late maturity hybrids were revealed: КРF-25; КРF-22; МРF-97; TsКR-25; YuTs-8 with the immixture of Fortunella margarita and C. citrangeqwat. From recurrent and inter-hybrid hybridization were marked out promising forms of mandarin with positive features such as early ripening, average fruit mass and a high tasting assessment. The greatest breeding value is represented by hybrids derived with the immixture of the most frost-resistant ccongeners of the citrus Poncirus trifoliata, however, from 5.0 % to 6.25 % of promising samples were selected in these families. All forms have breeding value for further work on creating winter hardiness varieties of mandarin.

Examination of drought stress of two genotype maize hybrids with different fertilization

In the growing season of 2019, we analysed stress resulting from climatic factors on maize hybrids of different genotypes, with the aim of gaining a better understanding of the physiological responses of each hybrid, which might support the elaboration of a cost-effective irrigation plan.
 Our experiments were carried out at the Látókép Experimental Station of the University of Debrecen on calcareous chernozem soil in a small-plot long-term field trial with strip plot design. In the scope of the experiment, N-fertilizer doses were applied as basic fertilizer and top-dressing in addition to the non-fertilized (control) treatment. The 60 and 120 kg N/ha doses applied as basic fertilizers in the spring were followed by top-dressing in the V6 phenophase with a +30 kg N/ha dose. Measurements were carried out with the involvement of the Renfor early (FAO 320) and Fornad (FAO 420) late maturity hybrids-
 The stomata of the plants became more and more closed with the progression of the phenological phases; their stomatal conductance decreased. However, the hybrids responded differently to environmental stress. In the case of the Renfor hybrid, the highest conductance (669 mmol/m2-s) was recorded in the V12 phenophase with the 150 kg N/ha treatment. The stomata were more open due to the high turgor pressure, allowing plants to evaporate properly. The plant was in its worst physiological condition on 2nd July, at the time of the appearance of the last leaf in the case of the 120 kg N dose (224 mmol/m2-s). The value measured in the V12 phenophase has already shown that the stomata were closing due to the self-regulating system of the plant. It would have been necessary to dispense irrigation water following the measurement. This confirms the finding that water stress can be prevented by measuring stomatal conductance.
 In the case of the Fornad hybrid, stomatal conductance was the highest on 12th June (630 mmol/m2-s) in the 90 kg N/ha treatment and it was the lowest (183 mmol/m2-s) in VT (emergence of the last leaf) phenophase in the 60 kg N/ha treatment. In this case, the appropriate time for applying irrigation water would have been early July, when the conditions for the plants were still adequate. Subsequently, the stomata began to close due to a reduction of the water resources available to them.
 There was a significant correlation between soil moisture and stomatal conductance, as well as between temperature and stomatal conductance.

تاثیر کمآبیاری بر عملکرد و اجزای آن در هیبریدهای ذرت دانهای (Zea mays L.)

با توجه به کمبود آب و مصرف زیاد آب در هیبریدهای دیررس ذرت، بررسی رشد، عملکرد و مصرف آب در هیبریدهای این گیاه ضروری می باشد. از این رو به‌منظور بررسی اثرات کم‌آبیاری بر عملکرد و اجزای عملکرد هیبریدهای ذرت دانه‌ای، آزمایشی به صورت کرت‌های خردشده در قالب طرح بلوک کامل تصادفی با سه تکرار، طی دو سال زراعی 4-1393 اجرا شد. کرت‌های اصلی به سطوح آبیاری (100، 80 و 60 درصد نیاز آبی) و کرت‌های فرعی به هیبریدهای ذرت (شامل دو هیبرید دیررس(KSC705, KSC704)، دو هیبرید متوسط‌رس (KSC500, KSC400) و دو هیبرید زودرس((DC370, KSC260) تخصیص داده شدند. نتایج نشان داد که عملکرد و اجزای عملکرد همه هیبریدها در مواجهه با شرایط کم-آبی، به طور معنی‌داری کاهش یافت، به‌طوری که در سال اول در هیبرید KSC705 (دیررس) و هیبرید KSC400 (متوسط‌ رس)، کاهش آبیاری از 100 به 60 درصد نیاز آبی، کاهش حدود 20 درصدی عملکرد را به دنبال داشت. در صورتی که در هیبرید زودرس کاهش آبیاری از 100 به 60 درصد نیاز آبی کاهش چندانی در عملکرد ایجاد نکرد. در سال دوم کاهش آبیاری از 100 به 60 درصد نیاز آبی در هیبرید KSC705 (دیررس)، KSC400 (متوسط‌ رس) و DC370 (زودرس) به ترتیب منجر به کاهش 24، 28 و 24 درصدی عملکرد شد. برتری عملکرد در هیبریدهای دیررس متاثر از برتری صفاتی مانند ارتفاع بوته، تعداد ردیف بلال، تعداد دانه در ردیف، وزن 300 دانه، شاخص برداشت و عملکرد زیست‌توده بود، با وجود این با اعمال کم‌آبیاری شدید، این برتری در بین هیبریدها معنی‌دار نبود. لذا به نظر می رسد که بتوان هیبریدهای دیررس را برای مناطق بدون محدودیت آب و هیبریدهای متوسط‌رس را برای شرایط با محدودیت آب استفاده کرد.

INFLUENCE OF FERTILIZERS AND GROWTH REGULATOR ON THE CHANGE OF BIOCHEMICAL PROPERTIES OF HYBRIDS OF ONION DURING STORAGE

Research staff All-Russian Scientific Research Institute of Vegetable Growing – Branch of the Federal State Budgetary Scientific Institution Federal Scientific Vegetable Center in collaboration with Russian state agrarian University – Moscow Timiryazev agricultural Academy conducted research (2014-2016) on the effect of fertilizers and plant growth regulators on changes in the quality of onions of the Pervenets F1, Bennito F1 hybrids and Poisk 012 F1 during storage. As a result of research, the greatest effect was obtained from the complex application of N90P90K90 in combination with trace elements (tenso-cocktail) and a growth regulator Zircon. This system allowed to obtain high biochemical parameters of onions. At the end of the 7 months of storage (October-may), the highest dry matter and sugar content and the minimum nitrate content was observed in Pervenets F1 onions, as well as in hybrid Bennito F1. In the latematuring hybrid onions Poisk 012 F1 at the end of storage, the dry matter content decreased to 6,8-7,3%, sugars to 3,6-4,1%, vitamin "C" to 3,2-4,9 mg%, and nitrates increased to 92,1 mg/kg, which led to a decrease in product quality and large losses of onions from diseases and natural losses (up to 48-59%). The main reason for these losses was the lack of maturity of bulbs,low solids and sugars during harvest. It is obvious that for long-term storage it is necessary to use bulbs with a dry matter content of at least 10%. It was found out that feeding of onions during the beginning of the formation of food organizations with potassium nitrate, treatment with a growth regulator of Zircon and a complex of microelements of tenso-cocktail contributes to better preservation of the quality of onions.

Molekularni diverzitet i polimorfizam mikrosatelitskih markera savremenih hibrida kukuruza

The aim of this study was to estimate genetic diversity of 97 modern maize hybrids cultivated in Serbia with 12 microsatellite markers. In total, 89 alleles were detected, with the average of 7.4 alleles per locus. The polymorphic information content ranged from 0.42, for umc1792, to 0.81, for dupssr10, with an average of 0.64. The pairwise relatedness Ritland's values varied between 0.787 and -0.129. Eight markers were sufficient to differentiate hybrids with unique genotypes. A principal coordinate analysis distinguished early and late maturing groups of hybrids, although the observed differentiation between groups was low (Fst = 0.4%). Two markers, bnlg1556 and umc1075, contributed most to the discrimination between early and late genotypes. The values of parameters of molecular genetic diversity were higher in early than in late maturing hybrids, indicating broader genetic basis of the former. A high level of polymorphism of the markers indicates their suitability for fingerprinting.

Hybrid Maturity Influence on Maize Yield and Yield Component Response to Plant Population in Croatia and Nebraska

Maize (Zea mays L.) yield component analysis is limited. Research was conducted in 2012 and 2013 at Zagreb, Croatia and Mead, Nebraska, United States with the objective to determine the influence of environment, hybrid maturity, and plant population (PP) on maize yield and yield components. Three maturity classes of maize hybrids were produced at five PP ranging from 65,000 to 105,000 plants ha−1 under rainfed conditions. Yield, ears m−2, rows ear−1, ear circumference, kernels ear−1, kernels row−1, ear length, and kernel weight were determined. Average yield was 10.7 t ha−1, but was variable for hybrids across PP. The early maturity-hybrids had lesser ear circumference, more kernels ear−1, greater ear length, and fewer rows ear−1 than mid- and late-maturity hybrids. Kernels ear−1 had the highest correlation with yield (r = 0.47; P < 0.01 for early-maturity hybrids; r = 0.55; P < 0.01 for the mid- and late-maturity hybrids). Path analysis indicated that ears m−2, kernels ear−1 and kernel weight had similar direct effects on yield for early-maturity hybrids (R = 0.41 to 0.48) while kernels ear−1 had the largest direct effect (R = 0.58 versus 0.32 to 0.36) for the midand late-maturity hybrids. Rows ear−1 had an indirect effects on yield (R = 0.30 to 0.33) for all hybrids, while kernels row−1 had indirect effect (R = 0.46) on yield for mid- and latematurity hybrids. Yield component compensation was different for early-maturity hybrid than the mid- and late-maturity hybrids, likely due to the proportion of southern dent and northern flint germplasm present in these hybrids.

English

This study was carried out to evaluate and assess the phenotypic correlation between the primary and secondary weevil resistant traits of 20 drought tolerant (DT) late maturing maize hybrids (LHYB) to weevil (Sitophilus zeamais Motschulsky) damage. Well-conditioned experimental samples with uniform grain moisture content were infested with 32; 10 to 14 day old weevils in the controlled temperature and humidity (CTH) environment for 55 days. Data were collected on kernel volume (KV) and grain hardness (GH) at the start of the experiment, percent weevil mortality (%WM) at the 21st day and percent grain weight loss (%GWL) and F1 weevil progeny emergence (F1WPE) at the 55th day of oviposition. Data were collected on starch, oil and protein content to confer resistance to weevil damage. There were highly significant differences (P<0.001) in F1WPE and %GWL, (P<0, 01) in KV while no significant differences were observed for %WM and GH. The obtained data confirmed that, there was a positive and significant correlation between F1WPE and %GWL, while a negative and significant correlation was observed between F1WPE and %WM. Hybrids CZH131022, CZH131003, CZH132064, CZH132069 and CZH132068 were the top five weevil resistant while hybrids CZH132066, CZH132065, CZH132074, CZH131008 and CZH132063 were the top five most susceptible. Key words: Controlled temperature and humidity, late maturing maize hybrids, Sitophilus zeamais.

Economic water use efficiency of corn (Zea mays L.) hybrids as affected by irrigation regimes: a case study in West Iran

ABSTRACTWater deficit stress is the main limiting factor in corn production in different regions of Iran. Choosing appropriate corn hybrids and well-managed irrigation practices will result in significant water savings (WS) and good outcomes. Therefore, a randomized complete block design arranged in split plots with four replications was used to evaluate the effect of irrigation regimes on some agronomic traits of corn hybrids. Three different irrigation regimes (irrigation after depleting 60%, 70%, and 80% of field capacity (FC) as water deficit stress, mild water deficit stress and well-irrigated treatment, respectively) were allocated to main plots and four grain corn hybrids (KSC 500, KSC 647, KSC 700, and KSC 704) were randomized in subplots. The results indicated that grain yield (GY), harvest index (HI), and relative water content (RWC) decreased, whereas water use efficiency (WUE), WS, and irrigation efficiency (IE) increased, with increasing water deficit stress intensity. Irrigation after depleting 70% of FC caused the highest economic WUE (1.01 kg grain m−3). In addition, late maturing hybrids (KSC 700 and KSC 704) showed higher values of all measured traits, except for HI, compared to mid-maturing hybrids (KSC 647 and KSC 500).

Progress in stacking aflatoxin and fumonisin contamination resistance genes in maize hybrids

Contamination of maize grain with mycotoxins including aflatoxin and fumonisin poses a threat to human health and livestock. The objectives of this study were to determine the current status of incidence of ear rot causing fungi, which are associated with mycotoxin contamination, in southern African maize hybrids, and to check whether or not mycotoxin resistance genes can be stacked in a single product. The 327 hybrids were evaluated under natural conditions in replicated trials over two seasons at Cedara Research Station, which is hot spot site for ear rot diseases. Concurrently, aflatoxin and fumonisin resistant tropical maize inbred lines were crossed with South African adapted inbred lines. The resultant 72 single crosses were evaluated for fumonisin contamination, while 44 three-way crosses and their progenies (146 S2:3 families) were evaluated for both aflatoxin and fumonisin contamination under artificial inoculation. The Fusarium verticillioides was the most prevalent ear rot causing fungus, followed by Stenocarpella maydis, F. graminearum and Aspergillus flavus. The late maturing hybrids were more susceptible to ear rots contamination than their earlier counterparts. Stacking of mycotoxin contamination resistance genes was successful because five experimental single cross hybrids consistently accumulated low fumonisin levels (<4 ppm), both in the greenhouse and field trials. Three 3-way crosses displayed low contamination levels for both aflatoxins (<5 ppb) and fumonisins. Four S2:3 families accumulated low levels of both aflatoxins and fumonisins below the legal limits of 5 ppb and 4 ppm, respectively. Therefore significant progress can be realised in breeding mycotoxin resistant maize hybrids.

Utilizing Dominant Early Maturity Genes of Sterile Line UP-3s in Hybrid Rice Breeding to Avoid High Temperature Season

A new sterile line UP-3s, which carries the Dominant Early Maturity Gene (DEMG), was bred on the farm of University of Arkansas at Pine Bluff (UAPB). UP-3s and two check sterile lines, Jin23-A and Xie-A which do not carry the Dominant Early Maturity Gene, were crossed with a group of different maturity restorer lines, PB-1R, PB-5R, PB11, PB-13R, PB-20, PB-21, PB-22R, and PB-23R. Eighteen new hybrid rice combinations of these crosses were then tested at UAPB in 2012 and 2013. The results showed that panicle differentiation (PD) of hybrids from female parent UP-3s (DEMG) crossed with the 8 male parents, were earlier than the hybrids from female parent Jin23-A or Xie-A crossed with the 8 male parents. The PD of these earlier hybrids was before Jun 25 and heading was before July 20. Early PD and heading avoided the high temperature (over 34˚C) period which usually occurs after July 20 in Arkansas. The yields of these earlier maturity hybrids with female parent UP-3s were higher than those of the late maturity hybrids thatwereF1 progeny of sterile lines Jin23-A or Xie-A (these two female parent checks with non-DEMG). These results showed that the DEMG sterile line UP-3s can be adopted in making crosses with later ma- turity restorer lines to obtain earlier maturity hybrids to avoid the high temperature period in Arkansas.

Early and Late Maturing Grain Sorghum under Variable Climatic Conditions in the Texas High Plains

Abstract. In the Texas High Plains, variable climatic conditions prevail between and within growing seasons. As this area continues to experience drought conditions and water resources for irrigation become more limited, sorghum [Sorghum bicolor (L.) Moench] production may become a more popular choice to sustain profitable crop water productivity with limited water. Regional sorghum production functions are helpful in strategizing adaptation methods for coping with climatic variability, but new varieties often exhibit new production functions. This article compares sorghum responses of grain yield, evapotranspiration (ET), water use efficiency (WUE), and irrigation water use efficiency (IWUE) of a late maturing (LM) and early maturing (EM) hybrid during three recent growing years exhibiting climatic variability (2009-2011). The hybrids were irrigated at levels of 80%, 55%, 30%, and 0% replenishment of soil water depletion to field capacity (FC). Mean maximum daily air temperatures and mean daily reference evapotranspiration (grass) for the 2009 (28.2°C, 6.5 mm d-1) and 2010 (28.6°C, 6.4 mm d-1) growing seasons were similar; in 2011, these parameters were considerable greater (32.6°C and 8.8 mm d-1, respectively). For both hybrids, dry grain yields were greatest in 2009 in the I80% treatment at 9.80 and 8.04 Mg ha-1 for the LM and EM hybrids, respectively. For irrigation treatment amounts of 80% replenishment of soil water to FC, grain yields in the LM hybrid were always greater compared with the EM hybrid. However, WUE in the EM hybrid in 2009 and 2011 was 27% and 29% greater, respectively, than in the LM hybrid. Grain yield responses in both hybrids were most sensitive to the exceptional drought year of 2011 where irrigation applied at less than 80% replenishment of soil water to FC greatly reduced grain yields. Irrigation applied at less than 55% replenishment produced minimal to no grain yields.

Simulation of maize top dry matter and leaf area index at different applied water and fertilizer levels

Crop simulation models are mathematical representations of plant growth processes as influenced by interactions among genotype, environment, and crop management. Evaluation of developed simulation models for management of applied water and nitrogen in field are compulsory. In this paper, the model of MSM2 (maize simulation model) was evaluated and validated based on two years experimental data. The planted cultivar was SC704 and late maturity hybrid. Three nitrogen fertilizers and four irrigation water treatments were considered for model evaluation. The model subroutines were investigated based on the measurements of soil and plant characteristics in the experiment conducted in the two years. Leaf area index (LAI) and top dry matter (TDM) production were evaluated and validated at different days after planting by measured data. Results showed that the model could predict TDM and LAI fairly well. The resulted values of model agreement index (d) and mean bias error (MBE) for all treatments showed an overall good result in two experimental years. Validation results showed the average values of d between measured and predicted TDM and LAI are 0.97 and 0.98, respectively for different treatments. Comparisons between measured and predicted values by current model indicated favorable validation.

The Influence of Hybrid Maturity and Planting Date on Sweet Sorghum Productivity during a Harvest Season

If sweet sorghum [Sorghum bicolor (L.) Moench] is to be successfully deployed for sugar and biofuel production, agronomic systems must be developed that maximize the duration of the harvest season. Using available sweet sorghum hybrids, the goal of this study was to determine optimum planting dates and hybrid maturity selection to maximize the duration and yield of a harvest season for a subtropical production environment. Ten sweet sorghum hybrids representing three maturity classes (early, medium, and late) and three planting dates (April, May, and June) were evaluated in replicated trials in 2010 and 2011 in College Station, TX, and each maturity class was harvested to maximize biomass and sugar yields. At this location, sweet sorghum hybrids can be continually harvested from late July to early November. During this time, sugar yields are lowest at the beginning of the season (2.6 Mg ha−1) and highest from late August through early October (5.3 Mg ha−1). As expected, yields are maximized by medium and late maturing hybrids planted in April, but early maturity hybrids and late planting dates are necessary to extend the range of the harvest season. The harvest season of sweet sorghum in this environment is very complementary to the sugarcane (Saccharum officinarum L.) harvest season, indicating that these two crops could be grown and harvested in sequence to extend a mill season in most regions of the world where sugarcane is produced.

Modification and validation of maize simulation model (MSM) at different applied water and nitrogen levels under furrow irrigation

The model MSM (Maize Simulation Model) was modified and validated, using data on furrow irrigation in Fars province in Iran during 2003 and 2004. The planted cultivar was SC704 (single cross) a late maturity hybrid. Three nitrogen levels (300, 150, and 0 kg N ha−1 as urea) and four irrigation treatments (applied water at 1.2, 1.0, 0.8, and 0.6 ratios of potential maize water requirements as I4, I3, I2, and I1 treatments, respectively) were considered. The potential water requirements were estimated based on the differences between soil field capacity and measured soil water contents at root depth in the I3 treatments before irrigation. The MSM model was modified based on field data in 2003 as: (i) Modification of root N uptake based on soil water pressure head and van Genuchten soil parameters for soil moisture retention curve α, and (ii) modification of grain yield prediction based on seasonal plant stover nitrogen uptake and grain N content. Model subroutines, i.e. leaf area index, dry matter production, prediction of soil water contents at different depths and at different days after planting did not require any modifications. Comparisons between measured data and predicted values by the modified model indicated favorable validation.

Frequency and Incidence of Pyrenochaeta terrestris in Root Internodes of Different Maize Hybrids

The frequency and incidence of Pyrenochaeta terrestris and symptom type on the roots of each internode of four maize hybrids of different maturity groups were studied 70 days after sowing. The fungus developed in the roots of all developed internodes (from the primary to the sixth or seventh internodes of all tested hybrids). The average frequency and incidence of P. terrestris in the roots of late and medium early maturity hybrids ranged from 29.5 to 55.2% and from 11.8 to 22.7%, respectively. The highest frequency of the fungus was at the 2nd root internode (93.3%), and its greatest incidence was detected in the mesocotyl of the medium early hybrid H-1 (56.9%). Necrosis predominated in the roots of the medium early (i.e. medium late maturity hybrids, 44.5% and 44.3%, respectively), whereas reddish pink symptoms were recorded in the roots of the late hybrids (51% and 42.5%). Because the fungus always produces a distinctive red pigment on carnation leaf agar (CLA) in a light regime, these conditions can be recommended for the reliable identification of P. terrestris, even if pycnidia are not formed. These are the first reports of the successive distribution of the fungus in each maize root internode of different hybrids, as well as the use of CLA medium in the identification of the P. terrestris.