The YABBY gene family and abaxial cell fate

The establishment of abaxial-adaxial polarity in lateral organs involves factors intrinsic to the primordia and interactions with the apical meristem from which they are derived. Recently, a small plant-specific family of genes, the YABBY gene family, has been proposed to specify abaxial cell fate. Each asymmetric above-ground lateral organ expresses at least one member of the family in a polar manner, and loss- and gain-of-function studies indicate that they are sufficient to specify abaxial cell fate and that they act in both distinct and redundant manners.     

Differentiating Arabidopsis Shoots from Leaves by Combined YABBY Activities

In seed plants, leaves are born on radial shoots, but unlike shoots, they are determinate dorsiventral organs made of flat lamina. YABBY genes are found only in seed plants and in all cases studied are expressed primarily in lateral organs and in a polar manner. Despite their simple expression, Arabidopsis thaliana plants lacking all YABBY gene activities have a wide range of morphological defects in all lateral organs as well as the shoot apical meristem (SAM). Here, we show that leaves lacking all YABBY activities are initiated as dorsiventral appendages but fail to properly activate lamina programs. In particular, the activation of most CINCINNATA-class TCP genes does not commence, SAM-specific programs are reactivated, and a marginal leaf domain is not established. Altered distribution of auxin signaling and the auxin efflux carrier PIN1, highly reduced venation, initiation of multiple cotyledons, and gradual loss of the SAM accompany these defects. We suggest that YABBY functions were recruited to mold modified shoot systems into flat plant appendages by translating organ polarity into lamina-specific programs that include marginal auxin flow and activation of a maturation schedule directing determinate growth.     

不同育性三角梅品种之间的形态、花粉活力、造访昆虫及黄酮醇含量的比较研究

三角梅高度不育,到目前为止其不育机理仍未理解透彻。本研究通过比较三角梅中可育和不育品种之间的生殖器官特征、花粉的活力、造访昆虫以及花粉中的类黄酮积累差异,为揭示其不育机理提供更多的证据。四个可育和两个不育三角梅品种的花萼管比较结果显示,可育品种的花萼管饱满呈长卵形,而不育品种的花萼管细长管状。可育品种的花粉形态均匀,而不育品种的花粉大小不一。花粉活性结果显示,可育品种的花粉萌发率在11.1%~46.5%,不育品种的花粉在相同的培养条件下几乎不萌发。在可育和不育品种间,共有七种昆虫造访,但昆虫的种类没有表现出明显的差异和偏好。类黄酮积累调查结果显示山奈酚/槲皮素糖苷衍生物是花粉中的主要类黄酮组分。利用花粉荧光染料DPBDA对四个可育和两个不育三角梅品种花器官中的黄酮醇含量比较显示,可育材料中的两种黄酮醇的含量显著高于不育材料,花粉管尖端的荧光信号相比花粉管的其他位置更丰富。我们推测黄酮醇含量差异,特别是槲皮素含量可能对三角梅花粉的活力有一定的积极作用。     

Root Hair Deformation, Bacterial Attachment, and Plant Growth in Wheat-Azospirillum Associations

Seven Azospirillum strains induced more deformation of root hairs of wheat than did strains of Rhizobium leguminosarum, Azotobacter chroococcum, or Escherichia coli. Azospirillum sp. strain Sp245 caused the most deformation. Strain Sp245 (isolated from surface sterile roots of wheat) and strain Sp7 (isolated from the rhizosphere of a forage grass) were compared with regard to their effects on root hair deformation, their attachment to roots, and their effects on the growth of four wheat cultivars. The amount of deformation caused by the two strains in the four cultivars increased in the following order: cv. Tobari, cv. Tonari, cv. BH1146, cv. Lagoa. Strain Sp245 attached to the roots of all cultivars in low numbers, and attachment did not increase with time (up to 48 h). Strain Sp7 attached in higher numbers, and attachment increased with time. Inoculation of the four cultivars of wheat had pronounced effects on root mass measured at maturity. The magnitude of the effects in the four cultivars increased in the following order: Tobari, Tonari, BH1146, Lagoa; these effects were progressively more positive for strain Sp245 and progressively more negative for strain Sp7. Concentrations of N in wheat did not vary substantially between cultivars or strains. Concentrations of K and P did not vary substantially between cultivars but did vary between strains, Sp245 effecting increases and Sp7 effecting decreases.     

Contents of Sugars, Fruit Acids, Amino Acids and Phenolic Compounds of Apple Fruits i n Relation to their Susceptibility to Botryosphaeria ribis

Five apple cultivars showing different levels of susceptibility to Botryosphaeria ribis were used to study the relationship between susceptibility and contents of sugars, fruit acids, amino acids and phenolic compounds in the fruits at various stages of maturity. Immature fruits of all the cultivars tested were completely resistant until 10 July. The fungus grew better on the yellow-coloured cultivars than the red-coloured cultivars. The low amount of reducing sugars and also the high levels of fruit acids, amino acids and total phenols were found in immature apple fruits, irrespective of cultivar. No consistent differences between the cultivars were recognized with regard to the contents of soluble sugars, fruit acids and phenols in fruit flesh during the maturity of fruits. However, only the levels of total soluble amino acids in fruit flesh and of total phenols in fruit peel at late stage of maturity consistently varied between the cultivars. The dark red-coloured, resistant cultivars Miller spur and Starkrimson showed higher contents of amino acids and phenols in fruit tissues than did the yellow-coloured, susceptible cultivars.     

Comparison of chloroplast and mitochondrial DNA from five morphologically distinct Beta vulgaris cultivars: sugar beet,fodder beet,beet root,foliage beet,and Swiss chard

Summary Two cytoplasms, N and S, are used in the breeding of sugar beet, Beta vulgaris var. altissima. These cytoplasms can be distinguished by their mitochondrial DNA. In an attempt to detect new cytoplasms, we compared the restriction profiles of chloroplast and mitochondrial DNA from five different cultivars of Beta vulgaris. All restriction patterns of chloroplast DNA were identical. With the exception of sugar beet with S-cytoplasm, all cultivars studied showed the same restriction profile of mitochondrial DNA, indicating that these cultivars all contain the N-cytoplasm. These results are discussed with regard to the large morphological differences of the cultivars and the cytoplasmic variability found in natural populations of the wild beet, Beta maritima.     

Effects of Environments,Meloidogyne incognita Inoculum Levels,and Glycine max Genotype on Root-knot Nematode-Soybean Interactions in Field Microplots

Five soybean cultivars (Braxton, Gordon, Jeff, Bragg, and Wright) resistant to Meloidogyne incognita (Mi) and three susceptible cultivars (Coker 156, GaSoy 17, and Coker 237) were grown at two locations for four seasons in microplots with increasing initial soil population densities (Pi) of Mi. The resistant cultivars and Coker 156 yielded better than GaSoy 17 and Coker 237 at all Pi. Yield response was dependent on environmental conditions and at one location was stimulated on Braxton, Gordon, Jeff, and Bragg by low Pi. Although Mi reproduced well on all cultivars, the pattern of reproduction differed. Population densities of Mi leveled off after 90 days on GaSoy 17 and Coker 237 but were still increasing after 120 days on the resistant cultivars; population densities were lower on resistant than on the susceptible cultivars. The population density of Mi on Coker 156 after 120 days was intermediate between those on the other susceptible and on the resistant cultivars. Mi population densities followed the same pattern under varying environmental conditions.     

INCREASED CONCENTRATION OF SOIL CADMIUM AFFECTS ON PLANT GROWTH,DRY MATTER ACCUMULATION,Cd, AND Zn UPTAKE OF DIFFERENT TOBACCO CULTIVARS (NICOTIANA TABACUM L.)

Cadmium (Cd) is a toxic trace metal pollutant for humans, animals, and plants. Tobacco is a wellknown efficient accumulator of Cd and the genotypic differences in Cd uptake and the response to Cd was not determined. The objectives of this study were to investigate: 1) the effects of Cd on the growth and development of different tobacco cultivars; 2) the differences among tobacco cultivars in Cd concentration, uptake, and use for the phytoremediation of polluted soils with Cd; and (3) the interactions between Cd and Zn with respect to concentration and uptake. The Cd level affected the number of leaves and dry matter accumulation, and there were differences among the different cultivars that were used. Furthermore, some cultivars showed a higher reduction in growth than others, indicating that they are more sensitive to Cd level in the soil. Moreover, differences existed among the cultivars for the Cd concentration and uptake. There also were negative correlations between Cd and Zn concentrations; as Cd accumulation increased, Zn accumulation decreased, which showed that the two heavy metals were antagonistic. These results suggest that tobacco cultivars differed greatly in their growth and developmental responses to Cd and in the concentration and uptake of Cd and Zn. In addition, it is possible to use certain tobacco cultivars to lower the Cd concentration in the soil.     

Infectibility and sensitivity of UK raspberry, blackberry and hybrid berry cultivars to Rubus viruses

Six blackberry or hybrid berry cultivars and 19 raspberry cultivars were assessed for their infectibility with, and sensitivity to, graft inoculation with 10 distinct viruses found infecting Rubus in the UK. Cultivars were grafted with each of, two isolates of the pollen borne raspberry bushy dwarf virus (RBDV), five aphid borne viruses: black raspberry necrosis, raspberry leaf mottle (RLMV), raspberry leaf spot (RLSV), rubus yellow net and raspberry vein chlorosis (RVCV); and isolates of the nematode transmitted nepoviruses, arabis mosaic, raspberry ringspot, strawberry latent ringspot and tomato black ring. All tested cultivars were infectible with a resistance breaking isolate of RBDV but only about half of that number with the Scottish type isolate of the virus. The raspberry cvs Autumn Bliss, and occasionally Glen Garry and Glen Prosen, developed leaf yellowing symptoms following infection with RBDV, but none of the other infected cultivars showed obvious leaf symptoms when kept in a heated glasshouse during the growing season. All tested cultivars were infectible with each of the four viruses transmitted in nature by the aphid, Amphorophora idaei. Most were infected symptomlessly, but seven cultivars developed severe leaf spotting symptoms due to infection with RLMV or RLSV. All but one of the raspberry cultivars were infectible with RVCV, which is transmitted in nature by the aphid Aphis idaei, and almost all infected plants developed leaf symptoms; only one of the hybrid berry or blackberry cultivars tested was infected with RVCV. In tests with the four nepoviruses, all tested cultivars, except Tummelberry, were infectible with at least one or more of these viruses. However, cultivars responded differently to challenge inoculation with different isolates of individual nepoviruses. Several cultivars developed chlorotic leaf mottling following infection with some nepovirus isolates. The implications of these results for virus control are discussed in the light of the changing pattern of virus and virus vector incidence in the UK.     

Reproduction of Heterodera schachtii Schmidt on Resistant Mustard,Radish, and Sugar Beet Cultivars

The reproduction of a Wyoming population of Heterodera schachtii was determined for resistant trap crop radish (Raphanus sativus) and mustard (Sinapis alba) cultivars, and resistant and susceptible sugar beet (Beta vulgaris) cultivars in a greenhouse (21 °C/16 °C) and a growth chamber study (25 °C). Oil radish cultivars also were field tested in 2000 and 2001. In the greenhouse study, reproduction was suppressed similarly by the resistant sugar beet cultivar Nematop and all trap crop cultivars (P ≤ 0.05). In the growth chamber study, the radish cultivars were superior to most of the mustard cultivars in reducing nematode populations. All trap crops showed less reproduction than Nematop (P ≤ 0.05). In both studies, Nematop and all trap crops had lower Pf than susceptible sugar beet cultivars HH50 and HM9155 (P ≤ 0.05). In field studies, Rf values of radish cultivars decreased with increasing Pi of H. schachtii (r² = 0.59 in 2000 and r² = 0.26 in 2001). In 2000, trap crop radish cv. Colonel (Rf = 0.89) reduced nematode populations more than cv. Adagio (Rf = 4.67) and cv. Rimbo (Rf = 13.23) (P ≤ 0.05) when Pi was lower than 2.5 H. schachtii eggs and J2/cm³ soil. There were no differences in reproductive factors for radish cultivars in 2001 (P ≤ 0.05); Rf ranged from 0.23 for Adagio to 1.31 for Commodore for all Pi.     

Comparative photosynthesis,growth, productivity,and nutrient use efficiency among tall- and short-stemmed rain-fed cassava cultivars

Field trials under rain-fed conditions at the International Center for Tropical Agriculture (CIAT) in Colombia were conducted to study the comparative leaf photosynthesis, growth, yield, and nutrient use efficiency in two groups of cassava cultivars representing tall (large leaf canopy and shoot biomass) and short (small leaf canopy and shoot biomass) plant types. Using the standard plant density (10,000 plants ha⁻¹), tall cultivars produced higher shoot biomass, larger seasonal leaf area indices (LAIs) and greater final storage root yields than the short cultivars. At six months after planting, yields were similar in both plant types with the short ones tending to form and fill storage roots at a much earlier time in their growth stage. Root yield, shoot and total biomass in all cultivars were significantly correlated with seasonal average LAI. Short cultivars maintained lower than optimal LAI for yield. Seasonal P _N, across cultivars, was 12% greater in short types, with maximum values obtained in Brazilian genotypes. This difference in P _N was attributed to nonstomatal factors (i.e., anatomical/biochemical mesophyll characteristics). Compared with tall cultivars, short ones had 14 to 24 % greater nutrient use efficiency (NUE) in terms of storage root production. The lesser NUE in tall plants was attributed mainly to more total nutrient uptake than in short cultivars. It was concluded that short-stemmed cultivars are superior in producing dry matter in their storage roots per unit nutrient absorbed, making them advantageous for soil fertility conservation while their yields approach those in tall types. It was recommended that breeding programs should focus on selection for more efficient short- to medium-stemmed genotypes since resource-limited cassava farmers rarely apply agrochemicals nor recycle residual parts of the crop back to the soil. Such improved short types were expected to surpass tall types in yields when grown at higher than standard plant population densities (>10,000 plants ha⁻¹) in order to maximize irradiance interception. Below a certain population density (<10,000 plants ha⁻¹), tall cultivars should be planted. Findings were discussed in relation to cultivation and cropping systems strategies for water and nutrient conservation and use efficiencies under stressful environments as well as under predicted water deficits in the tropics caused by trends in global climate change. Cassava is expected to play a major role in food and biofuel production due to its high photosynthetic capacity and its ability to conserve water as compared to major cereal grain crops. The interdisciplinary/interinstitutions research reported here, including an associated release of a drought-tolerant, short-stem cultivar that was eagerly accepted by cassava farmers, reflects well on the productivity of the CIAT international research in Cali, Colombia.     

Screening for resistance in apple cultivars to lightbrown apple moth, Epiphyas postvittana, and greenheaded leafroller, Planotortrix octo, and its relationship to field damage

The mature leaves of 38 apple (Malus domestica Borkh.) (Rosaceae) cultivars were screened for resistance to laboratory colonies of Epiphyas postvittana (Walker) and Planotortrix octo Dugdale (Lepidoptera: Tortricidae) by measuring larval survival and development rate, and pupal weight, in no‐choice laboratory bioassays in early summer. There were few cultivar effects on larval mortality but Nevis 1, A40R04T119, and ‘Sir Prize’ reduced survival of E. postvittana. Effects on development time and weight were correlated, and were integrated into a single measure of resistance R_c. R_c varied greatly between cultivars for both leafroller species, and identified 15 and 11 cultivars with partial resistance to E. postvittana and P. octo, respectively. A further experiment with three of the cultivars in midsummer, using the laboratory colonies in comparison with new colonies (from field collected larvae), produced similar results for E. postvittana, but there was no survival of new colony P. octo larvae on two cultivars. These results for P. octo are consistent with other recent research showing extreme cultivar resistance and critical colony and seasonal influences. A series of 4‐year field trials with the 38 cultivars showed poor correlation between laboratory and field resistance for the dominant leafroller species in the field, E. postvittana. The combined data, however, identified ‘Red Dougherty’, ‘Sir Prize’, and A40R04T119 as potentially useful in breeding for resistance to this species. The implications of these findings for integrated pest management (IPM) programmes and for the breeding of leafroller‐resistant apple cultivars are discussed.     

Effect of Different Strains of Soybean Mosaic Virus on Growth, Maturity, Yield, Seed Mottling and Seed Transmission in Several Soybean Cultivars

Eighty soybeans (Glyane max Merr) cultivars, includingx a resistant line Oxley 615 were each inoculated with seven streams of soybean mosaic virus SMV. Susceptible cultivers produced smaller plants with delaved maturity, and reduced seed yield relative to the non inoculared plants Someptible cultivars had.a higher level of morrled seeds and seat transmission ot SMV from the morrled seeds than the resistance line Oxley 615. The SMV strain cultivar interaction was significant for all traits, suggsesting that soybean cultivars should be tested against specific SMV strains to determine their response to this virus.     

A comparison between yellow-green and green cultivars of four vegetable species in pigments,ascorbate, photosynthesis,energy dissipation,and photoinhibition

Yellow-green foliage cultivars of four vegetables grown outdoors, i.e., Chinese mustard (Brassica rapa), Chinese kale (Brassica oleracea var. alboglabra), sweet potato (Ipomoea batatas) and Chinese amaranth (Amaranthus tricolor), had lower chlorophyll (Chl) (a+b) (29–36% of green cultivars of the same species), total carotenoids (46–62%) and ascorbate (72–90%) contents per leaf area. Furthermore, yellow-green cultivars had smaller photosystem II (PSII) antenna size (65–70%) and lower photosynthetic capacity (52–63%), but higher Chl a/b (107–156%) and from low (60%) to high (129%) ratios of de-epoxidized xanthophyll cycle pigments per Chl a content. Potential quantum efficiency of PSII (F_v/F_m) of all overnight dark-adapted leaves was ca. 0.8, with no significant difference between yellow-green and green cultivars of the same species. However, yellow-green cultivars displayed a higher degree of photoinhibition (lower Fv/Fm after illumination) when they were exposed to high irradiance. Although vegetables used in this study are of either temperate or tropical origin and include both C₃ and C₄ plants, data from all cultivars combined revealed that F_v/F_m after illumination still showed a significant positive linear regression with xanthophyll cycledependent energy quenching (q_E) and a negative linear regression with photoinhibitory quenching (q_I). F_v/F_m was, however, not correlated with nonphotochemical quenching (NPQ). Yet, a higher degree of photoinhibition in yellow-green cultivars could recover during the night darkness period, suggesting that the repair of PSII in yellow-green cultivars would allow them to grow normally in the field.     

Effects of photoperiod, temperature and vernalization on the phenology and spikelet numbers of spring wheats

Fourteen cultivars of north temperate, Australian, Mexican and Rhodesian origins, were grown in eight treatments: 2-day-lengths (10 h and 14h) × two temperature regimes (18/13 °C and 25/20 °C) × two seed vernalization treatments (unvernalized and 28 days at 1–2 °C). Numbers of days to 50 % ear emergence, leaf numbers and spikelet numbers of the main shoots were recorded. The north temperate cultivars were the most sensitive to daylength: in long days their mean spikelet number was 15 and they headed in 40–50 days, while in short days they had a mean of 24 spikelets and failed to head in 100 days. The Rhodesian cultivars were the least sensitive, but nevertheless headed 20–30 days earlier and had three to five fewer spikelets per ear in long days. The effects of vernalization on the tropical cultivars were related to maturity class: they ranged from negligible in early cultivars such as Sonora 64 and Devuli to decreases of 20 days to heading and seven spikelets in late cultivars such as Mexico 120 and Cajeme 71 in long days. The effects of temperature varied with cultivar and with vernalization treatment. Early cultivars and vernalized late cultivars headed earlier and had fewer spikelets in the warmer regimes while unvernalized late cultivars tended to have more spikelets and headed later. It is suggested that some vernalization of these late cultivars took place in the cooler regime. The significance of the results for the understanding of the physiological basis of the adaptation of wheat cultivars to different climatic zones is discussed.