Late Genotypes Research Articles

Strawberry Cultivar Evaluation Using Mathematical Indices

Three mathematical indices were developed to estimate: a) potential for early dollar return or early ripening (IE), b) concentrated cropping (IC), and deviation or similarity of a genotype to known cultivars (ID). Early ripening genotypes with high yield early in the season will have larger IE values than late genotypes with lower yield early in the season. Genotypes with few harvests will have larger IC values than those requiring several harvests. The ID index helps to identify and group genotypes with similar characteristics. These indices condense large numbers of values or arrays of traits into single index values, thereby simplifying genotype comparisons.

Mathematical Indices for Comparing Small Fruit Crops for Harvest Time and Trait Similarity

Three mathematical indices were developed to estimate: 1) potential for early dollar return or early ripening (IE), 2) concentrated cropping (IC), and 3) deviation or similarity of a genotype to known cultivars (ID). Early ripening genotypes with high yield early in the season will have larger IE values than late genotypes with lower yield early in the season. Genotypes with few harvests will have larger IC values than those requiring several harvests. The ID index helps to identify and group genotypes with similar characteristics. These indices condense numerous values or arrays of traits into single index values, thereby simplifying genotype comparisons.

Growth and Yield of Maize Genotypes during Dry Seasons in Northern Nigeria

SUMMARYTwo tropical and one temperate genotypes of maize were grown during the cool dry winter seasons in northern Nigeria. The tall tropical genotypes produced a greater leaf area index and more above-ground dry matter, and so had a higher crop growth rate, than the dwarf temperate genotype. However, the early flowering temperate genotype yielded more grain than the late flowering tropical genotypes. Although the initial low winter temperatures prolonged the preflowering growth period in the tropical genotypes, the terminal high temperatures hastened maturity and were associated with poor grain filling.Maíz de temporada seca en Nigeria

Genetic Variation for Forage Yield and Quality among Grain Oat Genotypes Harvested at Early Heading

Few studies have evaluated grain oat for forage yield and quality when harvested before heading, even though this is the current recommended practice when oat is used as a companion crop. The purpose of this research was to assess the amount of genetic variation that existed among grain oat (Avena saliva L.) genotypes for forage yield and forage quality when harvested at early heading (2–3 spikelets emerged from the boot), and to evaluate the relationship between forage yield, forage quality, and nine other agronomic traits. Sixty four elite grain oat genotypes were evaluated in the field on a Piano silt loam (fine‐silty, mixed, mesic Typic Argiudoll) at Arlington, WI, in 1987 to 1989. There was substantial genetic variation for forage yield and forage quality traits as indicated by relatively large genotypic variance (σ2g) components. The σ2g for forage yield was six times as large as the genotype ✕ year interaction variance (σ2gy), while σ2g for acid detergent fiber (ADF) and neutral detergent fiber (NDF) were twice as large as the σ2gu. Although year ✕ genotype interaction mean squares were significant for all traits, relatively large σ2g and small σ2gy indicate that selection for forage yield and quality traits should be effective in this germplasm when based on multiple year evaluations. Tall, late genotypes typically had high forage yield and low forage quality. Phenotypic correlations between grain yield and forage yield (−0.29), and between grain yield and forage quality traits (−0.02 to 0.14) were small. Other agronomic traits had stronger associations with forage yield (r = −0.67 to 0.60) than with forage quality (r = −0.38 to 0.45). We concluded that grain genotypes must be evaluated individually before heading for forage quality to accurately assess their forage value.

Genotypic differences in nitrogen uptake, dry matter production, and nitrogen distribution in pumpkins (cucurbita moschatapoir.)

Abstract Thirteen inbred and hybrid pumpkin (Cucurbita moschata Poir.) genotypes, differing on the basis of harvest maturity, were evaluated for NO3‐uptake from solution, dry matter production, and distribution of absorbed N in plant parts, over the 8‐day time‐course corresponding to the period of the vine initiation stage. The pattern of NO3‐ removal from solution was linear in the early genotypes and curvilinear in late genotypes. Genotypic differences in NO3 ‐ absorption were found in early genotypes but not in late ones. In early genotypes, NO3 ‐ uptake from solution was greater in the Fl hybrid than in the parents, but no apparent relationship was found between parents and Fl progeny in their ability to absorb NO3 ‐ from solution. Genotypic differences in dry weight and total N accumulation in roots, stems, and leaves were larger in early genotypes than in late genotypes. Differences in total N concentrations in plant parts among early and late genotypes were small, and occurred only in leaves. As a ...

Growth analysis of spring-type oilseed rape

Abstract A quantitative analysis of growth, development and yield of eight genotypes of Brassica napus L. and two genotypes of B. campestris L. were conducted in 1980 field experiments in central Alberta. B. campestris L. reached all growth stages, except onset of stem elongation, earlier than B. napus L. and correspondingly had a shorter stem elongation period and seed formation period. B. campestris L. had higher leaf emergence rates during all growth periods. B. napus L. had greater crop dry weight at first flower and fifteen days after first flower and greater mean crop growth rate from seeding to first flower. Mean relative growth rates were higher in B. napus L. than B. campestris L. during all growth periods. B. napus L. had greater leaf area index at first flower and fifteen days after first flower, greater axillary branch leaf area index at first flower, greater leaf area duration from first flower to maturity of first pod, and greater axillary branch leaf area duration from first flower to maturity of first pod,than B. campestris L. Late maturing genotypes of B. napus L. had higher leaf emergence rates during all growth periods than did the earlier maturing genotypes, but were later in reaching first axillary branch leaf, first flower, first true leaf senesced and end of true leaves. This study confirmed other studies which indicated ‘number of days to first flower’ as a major factor in determining the time to maturity in both annual rapeseed species. Earlier maturing genotypes of B. napus L. had greater mean leaf area ratios from seeding to first flower, axillary branch leaf area duration, and mean relative growth rates over all growth periods. Late maturing genotypes had greater mean unit leaf rate from seeding to first flower, crop dry weight at first flower and fifteen days after first flower, mean crop growth rates over all growth periods and greater leaf area index at first flower and fifteen days after first flower. The greater axillary branch leaf area duration of earlier maturing genotypes of B. napus L. is advantageous since it coincides with seed filling. The usefulness of mean relative growth rate as a selection tool in breeding programs warrants further study. Given the greater efficiency of earlier maturing genotypes, they could be more productive at higher seeding rates than genotypes which are not as efficient.

Transpirational Cooling as a Screening Technique for Drought Tolerance in Oil Seed Brassicas

Twenty-two genotypes of five Brassica species (oilseed rape and mustard), consisting of two different maturity groups and differing in plant morphology, were grown on sandy soil without post-sowing irrigation during 1982–83 winter season. Canopy temperature (Tc minus air temperature (Ta, stomatal conductance ($) and osmotic adjustment were studied on two different dear days corresponding to the siliqua formation stage in early duration (137–150 d) and late maturing genotypes (151–165 d) of oilseed Brassicas. The absolute mid-day values of transpirational cooling (Tc–Ta) were relatively higher in B.juncea and B. carinata than in B. tomifortii, B. napus and B. campestris. Tc-Tm showed a genetic variability ranging from 0-5 to 4 °C for early maturing genotypes, and from 0–5 to 5 °C for late maturing genotypes. Mid-day Tc–Ta showed significant positive correlation with Kh osmotic adjustment and seed yield in Brassica cultivars. Early genotypes out-yielded the late maturing ones, despite the lower values of AT, and Tc–Ta at siliqua formation in the former rather than later group of cultivars. It is suggested that average mid-day Tc–Ta as observed with an infrared thermometer, could effectively be used as a technique to screen Brassica genotypes for drought tolerance under receding soil moisture conditions.

Flowering response of pearl millet to water stress during panicle development*

SUMMARYIn pearl millet, severe water deficit during the period of panicle development delays flowering. The flowering response of both main shoot and tillers to water stress during panicle development was investigated using four hybrids. Panicle initiation of all tillers occurred in the three early genotypes despite water stress. In the late genotype, however, panicle initiation of tillers occurred only after the release of stress. The delay in flowering due to water stress was more pronounced in the tillers than in the main shoot. However, the proportion of tillers producing an inflorescence was increased by water stress. Grain yield losses on the main shoot by water stress were compensated by an increase in tiller grain yields. Delay in flowering and buffering by tillers provide an important adaptive mechanism to overcome a period of drought stress prior to flowering.

Sorghum root growth and water-use as affected by water supply and growth duration

Early (‘58M’) and late (‘90M’) isogenic lines of sorghum (Sorghum bicolor L. Moench) were grown in a root observation field installation at Temple, Texas in 1976, in order to study the effect of soil moisture and growth duration on root development and plant water-use. The installation consisted of soil-filled steel chambers equipped with a glass panel and installed in retaining structures in the ground. Each chamber was lifted out of the ground for weighing and measuring roots visible on the glass panel. In all chambers, soil was irrigated to field capacity prior to planting. Two soil moisture regimes were then imposed — an irrigated treatment, wherein irrigation was applied whenever soil moisture content was reduced to 50% of available soil water; and a stress treatment, wherein no irrigation was applied and plants grew on stored soil moisture. Transpiration was considerably less for the early than for the late genotype in relation to the respective leaf area of the two genotypes. Transpiration demand was met without apparent plant stress, as long as the soil moisture content of the total soil volume was greater than 20% of available soil water. Below 20% of available soil water, transpiration was controlled mainly by a reduction in leaf area through leaf senescence. Total cumulative root length per plant and root length density were larger and root length density per unit leaf area was smaller for the late than for the early genotype. Root length density per unit of green leaf area increased under conditions of soil moisture stress due mainly to the reduction in green leaf area. Root distribution along the soil profile was highly skewed (higher root concentration at shallow than at deep soil layers) with irrigation and more homogeneous without irrigation. Root growth at shallow soil layers was promoted by irrigation. Root mortality of approximately two-thirds of the total cumulative root length produced by heading was recorded. Root mortality was not only associated with total plant senescence, but with plant age and rooting depth.

Ontogeny of centers containing luteinizing hormone-releasing hormone in the brain of platyfish (Xiphophorus maculatus) as determined by immunocytochemistry.

We have traced the development from birth to puberty of the ir-LHRH producing centers, the nucleus olfactoretinalis (NOR), nucleus praeopticus periventricularis (NPP) and nucleus lateralis tuberis pars posterior (NLT), in male sibling platyfish genetically determined by differing P alleles to mature at two different ages. In sexually immature fish of both genotypes ir-LHRH is first localized in the NOR in perikarya and neuronal fibers and in the NPP where it is limited to the fibers. At the onset of puberty in early maturing fish (11 weeks), ir-LHRH accumulates in perikarya and fibers of the NPP and NLT. Late maturing siblings first have ir-perikarya in the NPP and a few ir-fibers in the NLT at the same developmental stage but at a later age (25-26 weeks). Ir-perikarya are still not seen in the NLT in late-maturing fish even when maturation is complete. This pattern of a sequential development of the three ir-LHRH containing areas of the brain, which we refer to as a "cascade effect", is similar in early and late genotypes. It is directly correlated to stage of development and not to chronological age. It is clear that the appearance of LHRH producing brain centers precedes, and is presumably essential for, the completion of the development of pituitary gonadotrops and the subsequent maturation of the gonads. The functional significance of the NOR in puberty and reproduction and as a possible site of action for the P gene is discussed.

Effect of maturity on competitive ability in soybeans

The effect of maturity on competitive ability in two cultivars of soybeans (Glycine max (L.) Merr.) was evaluated. Maturity dates within a genotype were simulated by removing half the plants from pure stands at end of flowering and twice later at approximately weekly intervals. Simulation of the early maturity of an equal competitor gave a significant competitive advantage to the late genotype only 2 out of 15 times. The average effect from simulation of earlier maturity within the genotype was statistically significant, but small, especially since the assumed difference in physiological maturity was 27 days. Most genotypic difference in competitive ability probably are due to characteristics other than maturity.

The genetic control of the pituitary‐gonadal axis in the platyfish, Xiphophorus maculatus

AbstractA sex‐linked gene controls the age at which the gonadotropic zone of the pituitary gland develops and becomes physiologically active. The alleles for early (Pe) and late(Pl) differentiation are linked to pigment genes that serve as genetic markers. Pe may be marked by Sp, Dr, Sr, Ir and + and Pl by Br and N. Ir females (PePe) matured between 10 to 15 weeks of age and Br (PePl) females between 16 to 20 weeks. Dr (PePe) females had ripe ovaries six to eight weeks earlier than N Dr (PePl) females (8 to 12 weeks versus 16 to 20 weeks). The average age of sexual maturation was 12.5 weeks for Ir Ir (PePe) males, 20 weeks for Ir Br (PePl) and 26.5 weeks for Br Br (PlPl) males. Dr Sr (PePe) males reached maturity at 13.5 weeks and N Sr (PePl) males at 27.5 weeks. The transformation of the anal fin into a gonopodium which is under androgenic control, takes longest in the late maturing fish (Ir Ir, 3.8 weeks; Ir Br, 4.8; Br Br, 6.5; Dr Sr, 4.2; N Sr, 6.4). Similarly, the rate of development of the gonadotropic zone and of the gonad is protracted in the late genotypes. Eventually, the gonadotropic zone of early and late maturing fish are indistinguishable. The Pl factor linked to N delays sexual maturity to a greater extent than the one linked to Br suggesting that not all Pl factors are identical and that important allelic interactions may exist. The growth rate of immature males and females is the same, however it declines sharply in males (but not females) at the time of sexual maturity. This leads to significant differences in adult size between male genotypes. Female genotypes do not exhibit size differences and eventually become larger than all males. The development of the gonadotropic zone precedes, and is essential for, complete gonadal maturation. In the absence of a functional gonadotropic zone, oocytes developed through the oil droplet stage and were surrounded by active follicle cells and a prominent zona pellucida. Spermatogenesis proceeded up to the spermatocyte stage and the cells lining the efferent ducts displayed a modicum of activity. Some of our data suggest that low levels of androgens are present in all males as early as five weeks of age prior to the development of gonadotrops. The genes regulating the development of the pituitary‐gonadal axis may be an important factor in explaining the evolution of poeciliid fish.

Sorghum Root Morphogenesis and Growth. I. Effect of Maturity Genes1

Root development of two sorghum [Sorghum bicolor (L.) Moench.] maturity isogenic lines (early – 60 SM and late – 100 M) was closely studied in plants growing up to 38 days after emergence (DAE) in hydroponics. Each adventitious (crown) root was tagged upon appearance and periodically measured for length. Root diameters, root volume, leaf area, and transpiration were also measured periodically. Seminal roots and mesocotyls were removed on some plants at 10 DAE, in order to simulate the effect of some common fungal or insect damage in the field.The onset of initiation of adventitious roots occurred at 4 and 6 DAE in the early and late genotypes, respectively. Root initiation rates cycled with time, within a range of 0 to 1.5 roots‐plant‐l−day−1. Cycling of root initiation rates appeared to correspond with the formation of concentric whorls of these roots in the crown. Total number of adventitious roots at 38 DAE was 17 and 23 in the late and early genotypes, respectively. In the early genotypes, growth rate of adventitious roots that were initiated at an early stage was the same as for roots initiated later, being about 3 cm day−1 In the late genotype, growth rate of later initiated roots was slower than that of roots initiated earlier. Although the early genotype had a greater total adventitious root length per plant than the late one, the latter had a greater root volume than the former, due to greater number and growth of lateral branches.Removal of the seminal root and mesocotyl increased the number and growth of lateral branches of existing adventitious roots and subsequently increased root volume in the early genotype. Similar effects were not observed in the late genotype.

Grafting as a Tool in Soybean Breeding1

Grafting of soybean [Glycine Max (L.) Merr.] from different maturity groups was studied to determine its feasability for simplifying crossing. When grafted on early flowering genotypes, scions of later flowering genotypes flowered 21 to 50 days after grafts were made. About 95% of the grafts were successful.The grafting technique appears to be an excellent method of inducing earlier flowering on late genotypes to permit their use in a crossing program. It is also a means of producing seed on genotypes that otherwise flower too late for seed production in a particular geographical area.

Effects of temperature and photoperiod on flowering and yield components of lupin genotypes in the field

The effects of photoperiod and temperature and/or insolation on flowering and yield components were measured for 24 genotypes of five Lupinus species in the field. Environmental factors were varied by sowing on three dates (April 2, May 17, and July 1) and by extending natural photoperiod with artificial light. Lack of vernalizing temperature (<10�C) following early April sowing retarded flower initiation substantially in the midseason to late genotypes of Lupinus angustifolius and L. pilosus and to a lesser degree other species. Genotypes with no vernalization requirement flowered fastest following April sowing. Flowering of all genotypes was accelerated considerably by 24-hour photoperiod, L. luteus being the most responsive species. Number of flowers per primary inflorescence was reduced, and percentage of flowers setting pods increased, by treatments that led to earlier flowering. Number of seeds per pod and 20-seed weight were not affected by the treatments, except that higher temperatures increased 20-seed weight significantly in L. luteus and L. cosentini. Number of flowers, percentage flower set, and 20-seed weight were found to be the most important yield components in the primary inflorescences of lupins.

Flowering in Pisum. the Effect of Cotyledon Removal on Genotypes if E Sn Hr and if E Sn Hr

Photoperiod does not affect the flowering node of intact plants of the early pea genotypes If e sn hr and If E Sn hr but cotyledon removal converts if E Sn hr into a photoperiodically sensitive form flowering with the late genotypes under short days.

The relation between yield and the reproductive phase in cocksfoot (Dactylis glomerata L.) in a winter rainfall environment

Studies were made of six genotypes of Dactylis glomerata grown in defoliated clonal swards in the Mediterranean-type environment of southern Australia. Differences between genotypes in timing of reproductive phase stem elongation was the main cause of yield differences for 5 months of the growing season. This latter period compares with the 3–4 weeks for differentiation of ecotypes found in northern temperate regions, and is a result of the winter growing season and lower latitude. High yields were obtained under midwinter conditions from early genotypes. The yield of late genotypes was affected by moisture stress in the spring of some years, and their production was very erratic from year to year. The ranking of the genotypes was affected by the date of the previous harvest. Initiation of reproductive buds was variable between genotypes, and some genotypes carried initiated buds throughout the year.