16 research outputs found
Genetic Evaluation of Seedling Heat Tolerance in Sorghum
Surface temperatures of tropical soils at planting time, where sorghum
( Sorghum bicolor ) is a traditional crop, can exceed 50°C for
hours. Seedling heat tolerance is critical for adequate crop
establishment in the semi-arid tropics. Improvement of seedlings heat
tolerant genotypes would reduce crop losses due to sufficient plant
populations. The objectives of this study were to estimate seedling
tolerance to heat, determine individual parental contribution and
estimate additive, dominance and epistatic effects for seedling
tolerance. In our experiments, seedling heat tolerance termed heat
tolerance index (HTI) was defined as a ratio of resumed coleoptile
growth after a controlled heat shock, compared to normal growth.
Genetic parameters of HTI were determined by crossing four lines with
varying HTI, with three tester lines, and deriving F1, F2, F3, BC1 and
BC11 families for generation means analysis. Line IS20969 from Egypt
showed the highest HTI of 0.71, while 290R, an experimental line from
the University of Nebraska was the lowest at 0.51. Additive and
dominance effects contributed to coleoptile elongation under normal
conditions, but only additive effects were significant in recovery
growth. Epistatic effects were present in both conditions. General
combining ability (GCA) effects for HTI were highly significant in both
conditions, but specific combining ability effects were negligible.
These results indicate that it is possible to improve seedling heat
tolerance and, thus, improve sorghum variety and hybrid plant
populations in tropical areas where hot soil temperatures occur.Les températures en surface des sols tropicaux au moment des
semis, oĂč le sorgho est une rĂ©colte traditionnelle, peuvent
excéder 50°C pendant des heures. La tolérance de la
chaleur des plantes est critique pour l'établissement adéquat
de la culture dans les tropiques semi-arides. L'amélioration des
génotypes résistants à la chaleur de plantes
réduirait des pertes de récolte dues aux populations de
plantes suffisantes. L'objectif de cette Ă©tude Ă©tait
d'estimer la tolérance des plantes a la chaleur, déterminer
l'additif parental individuel de contribution et d'Ă©valuation, la
dominance et les effets épistatiques pour la tolérance des
plantes en utilisant des analyses de moyens de génération des
populations développées à partir de l'ensemble de
détail de parents. Dans nos expériences, la tolérance de
la chaleur des plantes l'index nommé de tolérance de la
chaleur (HTI) a été définie comme rapport de croissance
reprise de coléoptile aprÚs un choc commandé de la
chaleur, comparé à la croissance normale. Des paramÚtres
génétiques de HTI ont été déterminés en
croisant quatre lignes de différents HTI avec trois lignes
d'appareil de contrÎle, et dérivant les familles F1, F2, F3,
BC1 et BC11 pour la génération veut dire l'analyse. La ligne
IS20969 d'Egypte a montré le plus haut HTI de 0.71 tandis que
290R, une ligne expérimentale de l'université du
NĂ©braska, Ă©tait la plus basse Ă 0.51. L'additif et les
effets de dominance ont contribué à l'élongation de
coléoptile dans des conditions normales, mais uniquement les
effets additifs Ă©taient significatifs dans la croissance de
rétablissement. Les effets épistatiques étaient
présents dans les deux conditions. Les effets de combinaison
généraux de la capacité (GCA) pour HTI étaient
fortement significatifs dans les deux conditions mais les effets de
combinaison spécifiques de capacité étaient
négligeables. Ces résultats indiquent qu'il est possible
d'améliorer la tolérance de la chaleur pour des plantes
améliores et d'améliorer ainsi la variété de sorgho
et les populations de plantes hybrides dans des secteurs tropicaux avec
de fortes températures de sol
Risk-Efficient Production Plans Under Alternative Measures of Income Expectations
Decisionâmaking under uncertainty with income expectations conditioned on available information is contrasted with the standard risk modeling definiâ tion of expectations as mean income. Two MOTAD models are specified, a traditional MOTAD and one employing an ARMA model to develop conditional expectations. The analysis indicates that income variability may be reduced by conditioning expectations on relevant information
Pearl millet/cowpea cropping system yields and soil nutrient levels
Pearl millet [Penisetum glaucum (L.) R.Br.] and cowpea [Vigna
unguiculata (L.) Walp] are important crops in traditional bush-fallow
production systems in West Africa. Human population growth is forcing
producers to consider alternative cropping systems and fertilizer
application to meet food needs, by continuous, intercrop and rotational
cropping systems on pearl millet and cowpea grain and stover yield, and
maintaining soft nutrient levels. A long-term cropping system study
with nitrogen applications of zero 20 and 40 kg ha-1 was initiated at
the Cinzana Research Station near Segou, Mali in 1990. The field had a
leached tropical ferruginous (Ustalf) soil. Nitrogen fertilizer
application increased pearl millet and stover yield linearly per year,
but had no effect on cowpea. Rotation with cowpea increased pearl
millet grain yield by 17 to 31% each year between 1991 and 1995, but
had little effect on cowpea yield. Intercropping reduced yield of both
crops every year, but the Land Equivalent Ration indicated a 14 %
average increase in land use efficiency. After four years, soil of
plots with the different cropping systems had similar levels of
nutrients, except for phosphorous which was higher in continuous cowpea
plots. Soil of plots with all cropping systems had lower level of pH,
K, Ca, Mg and cation exchange capacity than fallow plots, indicating
that all cropping systems were mining soil of nutrients. This research
indicates that nitrogen fertilizer application up to 40 kg/ha and crop
rotation with cowpea increase pearl millet grain and stover yield.Le mil [Penisetum glaucum (L.) R. Br.] et le niebe [Vigna unguculata
(L.) Walp] sont des cultures importantes dans les systemes
traditionnels en Afrique de l'Ouest. La croissance demographique pousse
les Producteurs a considerer d'autres systemes alternatifs de culture
et l'utilisation des engrais chimiques pour satisfaire les besoins
alimentaires et maintenir le statut des elements nutritifs du sol.
L'objectif de cette etude etait de determiner les effects des systemes
de monoculture et de rotation sur la production de grains et de
biomasse du mil et du niebe et le niveau des elements nutritifs du sol.
Une etude du stem de culture de longue duree avec l'apport de zero, 20
et 40 kg/hectare a ete initiee a la Station de Recherche Agronomique de
Cinzana non loin de Segou au Mali en 1990. La parcelle experimentale
etait un sol du type "Sols ferrugimeux tropicaux lessives".
L'application de l'engrai azote a augmente le rendement grain et de
biomasse du mil de facon lineaire chaque annee, mais n'a eu aucun effet
sur la production du niebe. L'association du niebe au mil a reduit le
rendement des deux cultures chaque annee, mais le rapport de la surface
equivalente a indique une augmentation moyenne de 14% de l'efficacite
d'utilisation de la terre. Apres quatre annees de culture, les sols des
parcelles portant les differents systemes de culture avaient des
niveaux similaires d'elements nutritifs, a l'exception du phosphore qui
etait plus eleve dans les parcelles de monoculture du niebe. Les sols
des parcelles de tous les systemes de culture avaient des niveaux de
pH, K, Ca, Mg et la capacite d'echange cationique plus bas que ceux de
la jachere, indiquant ainsi que tous les systemes de culture etudies
minaient les sol de ses elements nutritifs. Cette etude montre que
l'appliation de l'azote a la dose de 40 kg/hectare et la rotation avec
le niebe augmente le rendement grain et de bimasse du mil
Designing crop technology for a future climate: An example using response surface methodology and the CERES-Wheat model
Adaptability and Reliability of Yield for Four Bell Pepper Cultivars Across Three Southeastern States
(Capsicum annuum L.) cultivars were evaluated for yield (total weight of marketable fruit) performance over 41 environments as combinations of 3 years, three planting dates, and seven locations across North Carolina, South Carolina, and Georgia. Cultural practices, including trickle irrigation and double rows planted on blackplastic- covered beds, were uniform across all environments, except for fertilization, which was adjusted at each location based on soil tests. Comparing production over 3 years between the mountain location and the Coastal Plain location in North Carolina, yields were lower on the Coastal Plain. Spring plantings provided higher yields than summer plantings at both locations. Yield increases were obtained from hybrid cultivars over that of the open-pollinated (OP) standard [âKeystone Resistant Giant #3â (KRG#3)] in the summer planting in the mountains compared to the Tidewater Coastal Plain. Across the three-state region, hybrid cultivar yields were higher than those of the OP cultivar for the second spring planting date in 1986 and 1987. Although the hybrid yields were higher than that of the OP standard, the hybrid âSkipperâ yielded less than the other hybrids (âGator Belleâ and âHybelleâ). âGator Belleâ generally out-yielded âHybelleâ at all locations, except in Fletcher, N.C. This difference may be related to the relative sensitivity of these two cultivars to temperature extremes, rather than soil or geographic factors, because there was a tendency for âHybelleâ yields to exceed âGator Belleâ in the earliest planting date. Based on the reliability index, the chance of outperforming KRG#3 (the standard) was 85% for âHybelleâ, 80% for âGator Belleâ, but only 67% for âSkipperâ