Plant Growth Habit Research Articles

Índice de seleção para escolha de populações segregantes de feijoeiro-comum

Os objetivos deste trabalho foram determinar a viabilidade de uso de um índice de seleção baseado em somatório de variáveis padronizadas no melhoramento genético do feijoeiro-comum e identificar as populações segregantes mais promissoras em produtividade de grãos, porte da planta e resistência ao acamamento, simultaneamente. Foram avaliadas populações segregantes obtidas por cruzamentos em esquema de dialelo parcial (6x6). Os genitores utilizados foram divididos em dois grupos. No grupo I, foram utilizados genitores com grãos do tipo carioca, de porte semiereto a prostrado. No grupo II, foram utilizados genitores com porte ereto, porém com grãos fora do padrão comercial carioca. As gerações F2 e F3 das combinações híbridas foram avaliadas em experimentos com delineamento de blocos ao acaso, com três repetições e semeadura em novembro de 2007 e fevereiro de 2008, respectivamente. Os dados relativos à produtividade de grãos, à nota de porte e à nota de acamamento foram padronizados (Zij) por parcela. A partir do somatório de Zij, obteve-se o índice de seleção para as três características conjuntamente. Constatou-se que o índice de seleção possibilita selecionar populações segregantes superiores, considerando simultaneamente a produtividade de grãos e as notas de porte e de acamamento. As populações segregantes CV III 8511 x BRS 7762 Supremo, CV III 8511 x RP 166 e CV III 8511 x RP 26 são indicadas para programas de melhoramento a fim de obter linhagens produtivas com plantas eretas e menor acamamento.

In vitro ecology of Calopogon tuberosus var. tuberosus (Orchidaceae) seedlings from distant populations: implications for assessing ecotypic differentiation1

In vitro culture techniques can be used to study the unique growth habits of plants as well as the ecological factors that influence seedling growth and development (i.e., in vitro ecology) such as adaptation to local environmental conditions. The in vitro seedling ecology of Calopogon tuberosus var. tuberosus from Michigan, South Carolina, and Florida was studied with emphasis on timing of corm formation and biomass allocation. In vitro seedling growth and development were monitored for 20 weeks. Corm formation was most rapid in Michigan seedlings, but was progressively delayed in southern populations. Similarly, biomass allocation to corms was highest in Michigan seedlings while south Florida seedlings exhibited the lowest corm biomass allocation. Shoot senescence in vitro also began earlier in more northern populations. The rapid corm formation and biomass allocation in seedlings from more northern populations represents an adaptive response to a shorter growing season. The relative differences in corm formation, biomass allocation, and shoot senescence in C. tuberosus seedlings suggest that in vitro common garden studies are useful to assess the degree of ecotypic differentiation among populations for a wide range of ecological factors. Additionally, these in vitro techniques can be transferred to numerous species worldwide.

Morphological variations of chaste tree (Vitex agnus‐castus) genotypes from southern Anatolia, Turkey

In this study, the extent and distribution of visual and morphological characteristics and diversity based on seven origin sites for 37 chaste tree (Vitex agnus‐castus) genotypes selected from the east coast of Antalya Province (southern Anatolia, Turkey) were determined. Plant size, growth habit, and flower colour were used as visual characteristics. Morphological characteristics included primary and secondary panicle lengths and flower numbers, petiole length, mid‐leaflet length and width, and flowering branch diameter. Genotypes differed significantly in both overall and within origin sites in terms of frequency for visual characteristics. Similar large diversities were recorded between and within origin sites for morphological characteristics. Pearson's coefficients revealed that there were several significant and positive correlations between morphological characteristics of V. agnus‐castus genotypes. Cluster and principal component analyses based on means of genotypes for morphological characteristics confirmed large variations between V. agnus‐castus genotypes.

Analysis of Genetic Structure in Widely Distributed Common Bean Landraces with Different Plant Growth Habits Using SSR and AFLP Markers

ABSTRACTThe genetic variation in common bean (Phaseolus vulgaris L.) landraces with different growth habits, which are grown over a wide and environmentally heterogeneous area in southern Italy, was studied to help define strategies for conservation of genetic resources. Accessions of three landraces, a'Marrozzo and Poverella with indeterminate growth habits, and Verdolino with a determinate growth habit, were scored for 30 simple sequence repeat (SSR) and 393 amplified fragment length polymorphism (AFLP) loci using eight primer combinations. Very low heterozygosity was observed, and all 73 plants analyzed showed different genotypes when comparing their alleles at the SSR or AFLP loci. The analyzed genotypes were clustered first according to plant growth habit and then in distinct groups according to landrace classification. Genetic differentiation among landraces was higher for AFLP (FST = 0.64) than for SSR loci (FST = 0.31), and variation within landraces was higher in a'Marrozzo, which is widely distributed over four river catchment basins. The proportion of alleles common to all three landraces was much larger for AFLP (62.34%) than for SSR (27.13%), while the alleles found in only one landrace were more frequent for SSR (47%) than for AFLP (8.14%). The large number of SSR and AFLP alleles shared between a'Marrozzo and Poverella (both with indeterminate growth habits) indicates their common evolutionary history.

Regional and Ecotype Traits in Lotus corniculatus L., with Reference to Restoration Ecology

To assess the relative importance of distance (geographical or ecological) as a consideration when collecting seeds for restoration projects, there is a need for more research on regional and ecotypic variation in a range of species. We used Lotus corniculatus L., a legume frequently included in grassland seed mixes, to investigate phenotypic variation between British accessions in a common garden experiment. The aim of this study was to investigate the effect of seed origin on plant phenotype and fecundity and to determine whether there was any evidence of correlation with distance (geographical or ecological) in populations grown from seed collected from different locations. Regional differences were detected in plant size, growth habit, pubescence, leaf shape, and fecundity. Geographical distance between sites was shown to be positively correlated with an increased difference in seed yield. Differences in size, growth habit, and leaf shape between paired habitats of origin within region and also between “ecotypes” were evident. However, there was no correlation between ecological distance and any of the measured traits. These findings suggest that: 1 Differences in phenotype and fecundity between geographically separated populations of L. corniculatus may be sufficient to lead to differences in survival and fitness when seeds are sown in a restoration environment. 2 Although it is important to consider geographical location, the choice of habitat within region is also important because phenotypic variation between ecotypes may have long-term consequences for plant persistence.

Plant growth habit, root architecture traits and tolerance to low soil phosphorus in an Andean bean population

The optimal plant growth habit and architecture of common bean (Phaseolus vulgaris L.) is dependent on environmental conditions. The objectives of this research were to determine if plant growth habit impacts a plant’s ability to grow in low P conditions, as measured by P uptake, seed yield, and P use efficiency and to determine if aboveground plant growth habit and root growth are associated at variable P soil levels. The study was carried out with recombinant inbred lines developed from an Andean intra-gene pool cross between a low P tolerant parent with an indeterminate growth habit (G19833) and a low P susceptible parent with a determinate growth habit (AND696). The population was grown for 2 years in low and sufficient P conditions in a field site in Darien, Colombia. In the first season, indeterminate lines had 15% more seed yield than the determinate lines in the low P treatment, whereas there was no difference by growth habit in the high P treatment. In the second season, seed yield and tolerance to low P was not influenced by growth habit. Root architectural characteristics such as root length density (RLD) and root surface area were 25% and 34% greater respectively in the indeterminate lines under P-sufficiency, whereas under low P, root architecture traits were not significantly different by growth habit. Root plasticity was higher in determinate lines, although RLD and root surface area did not play a significant role in tolerance to low P. Overall, the data were consistent with shoot growth habit as playing a complex and important role in adaptation to P-deficiency.

Genes controlling plant growth habit in Leymus (Triticeae): maize barren stalk1 (ba1), rice lax panicle, and wheat tiller inhibition (tin3) genes as possible candidates

Leymus cinereus and L. triticoides are large caespitose and rhizomatous perennial grasses, respectively. Previous studies detected quantitative trait loci (QTL) controlling rhizome spreading near the viviparous1 (vp1) gene markers on linkage groups LG3a and LG3b in two families, TTC1 and TTC2, derived from Leymus triticoides x Leymus cinereus hybrids. The wheat tiller inhibition gene (tin3) is located on Triticum monococcum chromosome 3 A(m)L near vp1. Triticeae group 3 is reportedly collinear with rice chromosome 1, which also contains the maize barren stalk1 and rice lax branching orthogene near vp1. However, previous studies lacked cross-species markers for comparative mapping and showed possible rearrangements of Leymus group 3 in wheat-Leymus racemosus chromosome addition lines. Here, we developed expressed sequence tag (EST) markers from Leymus tiller and rhizomes and mapped sequences aligned to rice chromosome 1. Thirty-eight of 44 informative markers detected loci on Leymus LG3a and LG3b that were collinear with homoeologous sequences on rice chromosome 1 and syntenous in homoeologous group 3 wheat-Leymus and wheat-Thinopyrum addition lines. A SCARECROW-like GRAS-family transcription factor candidate gene was identified in the Leymus EST library, which aligns to the Leymus chromosome group 3 growth habit QTL and a 324-kb rice chromosome 1 region thought to contain the wheat tin3 gene.

Identification of quantitative trait loci (QTL) for plant structure, growth habit and yield in lentil

Lentil quantitative trait loci (QTL) related to plant structure (branches at first node, height of first node, total number of branches, plant height), growth habit (flowering time, pod dehiscence) and yield (number of seeds, seed weight, seed diameter) were located using a F2 population of 113 individuals derived from the intersubspecific cross of Lens culinaris ssp. culinaris and L. c. ssp. orientalis. Several traits were found to be significantly correlated. Using interval and composite interval mapping a total of 23 QTL for nine quantitative traits were located. No QTL was identified for the number of F3 seed produced. Six QTL were positioned respectively in linkage groups III and VI, and five QTL in linkage group I. Each remaining group included one or two QTL, except groups VII and IX where no QTL was found. The multiple QTL model explained more than 80% of the observed phenotypic variance with logarithm of the odds (LOD) scores above 10 for three of the quantitative traits analyzed (branches at first node, flowering time, and dehiscence). For the remaining traits the phenotypic variance explained was relatively low, between the 50% and 20%, and the LOD scores ranged between 4 and 8. The possible homology between some QTL and other previously described is discussed in relation to their chromosomal location.

Forage quality, twig diameter, and growth habit of woody plants browsed by black rhinoceros in semi-arid subtropical thicket, South Africa

Rapid growth of the black rhino ( Diceros bicornis) population in the Great Fish River Reserve (GFRR), South Africa, has potential to negatively impact the semi-arid thicket vegetation that occurs in the reserve. Woody plants presenting nutritious twigs to twig-biting browsers are assumed to be potentially at greater risk of losing biomass than those that do not and should be considered in management protocols. We investigated plant growth habits, twig diameter and forage quality of woody species commonly browsed by black rhino in the GFRR to see if any fit a high risk profile. Samples of twigs 2, 6, 10 and 14 mm in diameter, and the leaves thereon, were collected during the wet season to determine the dry mass (DM), crude protein (CP) and neutral detergent fibre (NDF) concentrations of leaves and wood, as well as leaf:stem ratios (LSR). CP and LSR decreased while NDF and DM increased with twig diameter. Rates of change appeared to be greater for evergreen than deciduous species. Black rhinos foraging in the GFRR are therefore expected to inflict greatest biomass losses on deciduous species, especially ones with many long shoots. We recommend that relationships among forage quality and growth habits of woody species need to be better understood for the management of black rhinos in semi-arid subtropical thicket.

Altered Glucosinolate Hydrolysis in Genetically Engineered Arabidopsis thaliana and its Influence on the Larval Development of Spodoptera littoralis

The antiherbivore potential of the glucosinolate-myrosinase defense system found in plants of the order Capparales is heavily influenced by the types of hydrolysis products (e.g. isothiocyanates, nitriles) formed from the parent glucosinolates upon plant damage. However, comparison of the effects of glucosinolate hydrolysis products on insect herbivores has been hampered by the lack of suitable experimental tools for rigorous bioassays, such as intact plants differing only in the types of hydrolysis products they produce, or artificial diets that can accurately simulate glucosinolate hydrolysis. The wide array of molecular resources for Arabidopsis thaliana has facilitated the identification of several genes that play a role in glucosinolate hydrolysis. One of these encodes the epithio-specifier protein (ESP) that promotes the formation of nitriles at the expense of isothiocyanates in certain ecotypes of A. thaliana. We overexpressed the ESP cDNA from the nitrile-producing ecotype Landsberg erecta in the isothiocyanate-producing ecotype Columbia-0 to generate transgenic lines of A. thaliana that differed from wild-type plants in the type of glucosinolate hydrolysis products formed upon tissue damage, whereas parent glucosinolate profile and myrosinase activity levels, as well as plant morphology and growth habit, remained unchanged. Bioassays with the model generalist herbivore Spodoptera littoralis (Lepidoptera: Noctuidae) demonstrated that larvae reared on the nitrile-producing lines on average gained weight faster in the first larval stages than larvae that fed on isothiocyanate-producing control plants. Furthermore, larvae with medial growth rates showed a tendency to pupate earlier on the ESP-overexpressing plant lines. Together with the results of previous studies, these findings suggest that isothiocyanates are more effective defenses against insect herbivores than nitriles, and raise questions about what conditions select for nitrile formation in plants.

Evaluation of cold hardiness in two sets of near‐isogenic lines of wheat (Triticum aestivum) with polymorphic vernalization alleles

AbstractIn wheat, variation at the orthologus Vrn‐1 loci, located on each of the three genomes, A, B and D, is responsible for vernalization response. A dominant Vrn‐1a allele on any of the three wheat genomes results in spring habit and the presence of recessive Vrn‐1b alleles on all three genomes results in winter habit. Two sets of near‐isogenic lines (NILs) were evaluated for DNA polymorphisms at their Vrn‐A1, B1 and D1 loci and for cold hardiness. Two winter wheat cultivars, ‘Daws’ and ‘Wanser’ were used as recurrent parents and ‘Triple Dirk’ NILs were used as donor parents for orthologous Vrn‐1 alleles. The NILs were analysed using molecular markers specific for each allele. Only 26 of 32 ‘Daws’ NILs and 23 of 32 ‘Wanser’ NILs had a plant growth habit that corresponded to the marker genotype for the markers used. Freezing tests were conducted in growth chambers programmed to cool to −21.5°C. Relative area under the death progress curve (AUDPC), with a maximum value of 100 was used as a measure of death due to freezing. The average relative AUDPC of the spring habit ‘Daws’Vrn‐A1a NILs was 86.15; significantly greater than the corresponding winter habit ‘Daws’Vrn‐A1b NILs (42.98). In contrast, all the ‘Daws’Vrn‐A1bVrn‐B1aVrn‐D1b and Vrn‐A1bVrn‐B1bVrn‐D1a NILs (spring habit) had relative AUDPC values equal to those of their ‘Daws’ sister genotypes with Vrn‐A1bVrn‐B1bVrn‐D1b NILs (winter habit). The average AUDPC of spring and winter habit ‘Wanser’ NILs differed at all three Vrn‐A1, Vrn‐B1 and Vrn‐D1 locus comparisons. We conclude that ‘Daws’ and ‘Wanser’ have different background genetic interactions with the Vrn‐1 loci influencing cold hardiness. The marker for Vrn‐A1 is diagnostic for growth habit and cold hardiness but there is no relationship between the Vrn‐B1 and Vrn‐D1 markers and the cold tolerance of the NILs used in this study.

Dormancy relations and flowering of the strawberry cultivars Korona and Elsanta as influenced by photoperiod and temperature

Abstract Dormancy and flowering responses of the strawberry cultivars Korona and Elsanta have been studied in controlled environments. After short day (SD) floral induction for 5 weeks at temperatures ranging from 9 to 27 °C, long photoperiods only were required for optimal leaf and inflorescence growth and development at 18 °C, with no additional effect of chilling. However, with extended SD treatment for 10 or 15 weeks at 15 °C the plants entered the usual semi-dormant state typical for strawberry plants in late autumn, and subsequent long day (LD) conditions could not fully reverse the restrained growth habit. Extended SD treatment at 6 °C did not bring about this dormant state, indicating that the dormancy-inducing effect of SD is continuously nullified by such low temperature. When SD induced plants were forced under continued SD conditions, leaf and inflorescence growth were strongly restrained even in plants that had been chilled for up to 6 weeks. The restrained plant growth habit attained in SD, proved not to be a reliable indicator of the dormant state of the plants as it occurred also at low temperature. Floral induction in ‘Korona’ and ‘Elsanta’ was shown to have an obligatory SD requirement at temperatures ranging from 9 to 21 °C, while SD floral induction was marginal at 27 °C. The floral inducing effect of SD was also strongly reduced at temperatures below 9 °C. Application of these findings for multiple cropping of inherently single-cropping strawberry cultivars in winter season greenhouse production systems is discussed.

DEVELOPING PEACH CULTIVARS WITH NOVEL TREE GROWTH HABITS

Peach germplasm is rich in diversity for plant growth habit. Most of the growth habits in peach are the result of single gene changes and can he readily manipulated by breeders. In spite of this tact, there has been relatively little effort to genetically alter peach tree growth habit. The peach industry suffers from low productivity and lacks efficient high-density production systems as exist for apple. Alternate tree growth habits could be at least part of the solution for increasing peach productivity while maintaining high fruit quality. The characteristics of various novel peach tree growth habits have been demonstrated. Columnar and upright trees are particularly promising growth types for high-density production systems and several new cultivars have been recently released for grower test. Narrow-leaf trees that allow increased light penetration into the canopy and are more water use efficient also appear promising. Spur-type trees could change the way that peaches are grown and drastically reduce pruning. In the future, growers may have available an array of high quality and productive peach varieties with growth habits such as columnar, upright, spur, semi-dwarf, or narrow-leaf, suited to their particular needs and capabilities.

Reconstitution d'un « paysage de l'époque houillère » revue à la lumière des découvertes récentes sur les cuticules végétales fossiles

To date, plants with a climbing or scrambling growth habit are widely represented in equatorial forest ecosystems, with a warm and humid climate, with a variety of different species. Although it has been speculated repeatedly that several Late Carboniferous seed ferns applied the same growth strategies as modern vines and /or lianas, only few examples have been substantiated in sufficient details. Most Paleozoic seed ferns are reconstructed as free-growing erect trees. However, these last years, new discoveries about the growth habits of fossil plants have been highlighted on the basis of cuticular material. In this way, different types of climbing organs of seed ferns, reported on pteridosperm cuticles collected from the Stephanian basin of the Blanzy-Montceau (central France), have revolutionized the stereotype of “free-growing erect trees” that we had about these plants. These discoveries demonstrate the potential of cuticular analysis for the reconstruction of growth habits of fossil plants. Moreover they exemplify that climbing and scrambling became common life strategies among Late Carboniferous seed ferns. The increasing proportion of climbing seed ferns in the Stephanian, interpreted as an expression of changing structures of Late Paleozoic coal swamp forests, lead to modify the “classical” reconstructions of the Late Carboniferous landscapes.

Efeito do espaçamento e da cultivar de feijoeiro sobre a intensidade do mofo-branco e a sanidade de sementes

Dois ensaios de campo foram realizados para avaliar o efeito do espaçamento entre linhas (30, 45 e 60 cm) e entre plantas de feijoeiro com hábitos de crescimento diferentes, sobre a intensidade do mofo-branco e a sanidade de sementes. No primeiro, foi mantida a mesma população de plantas por área, 27 plantas/m², reduzindo-se o espaçamento entre plantas. No segundo ensaio, manteve-se o mesmo espaçamento entre plantas, que resultou em populações de 40, 27 e 20 plantas/m². A porcentagem de plantas infectadas e a severidade da doença não diferiram estatisticamente quanto ao hábito de crescimento da cultivar, ao espaçamento ou à interação entre eles, mesmo a incidência tendo atingido valores de 98,4% em 1998 e de 2,7% em 1999. A porcentagem de sementes infectadas não foi afetada pelo espaçamento, mas diferiu erraticamente em relação às cultivares; em 1998, a cultivar Pérola não apresentou sementes infectadas, o mesmo acontecendo com a cultivar Diamante Negro em 1999.

Variáveis multicategóricas na determinação da divergência genética entre acessos de pimenta e pimentão

A manutencao de acessos de Capsicum em bancos de germoplasma tem crescido em importância para preservacao da diversidade e uso em programas de melhoramento genetico. Este trabalho visou avaliar a divergencia genetica entre acessos de Capsicum spp. e verificar a eficiencia da utilizacao de medidas de dissimilaridade e da discriminacao de genotipos em especies, baseando-se em 13 variaveis multicategoricas. O experimento foi realizado em Campos dos Goytacazes, RJ, em blocos ao acaso com tres repeticoes utilizando 59 acessos com dez plantas por parcela, entre novembro/2001 e julho/2002. Os descritores considerados foram: cor do caule, da antera e da corola; numero de flores por axila; posicao da flor; habito de crescimento; cor do fruto imaturo e maduro; forma e epiderme do fruto; cor da semente e da folha cotiledonar; numero de loculos; constricao anular do calice e do fruto. Os dados foram obtidos pela moda de cada descritor seguindo-se os criterios do IPGRI. As analises realizadas foram: agrupamento pelo metodo de Tocher e Hierarquico do Vizinho Mais Proximo; Projecao das Distâncias no Plano e Analise Discriminante de Anderson. O metodo de Tocher diferenciou as especies de C. annuum var. annuum, C. annuum var. glabriusculum, C. chinense e C. pubescens, confirmando que os descritores qualitativos essenciais para a caracterizacao de Capsicum spp. devem ser utilizados no manejo de bancos de germoplasma. Os metodos de Tocher, Hierarquico do Vizinho Mais Proximo e Projecao das Distâncias no Plano foram concordantes e eficazes em agrupar acessos com pequena distância genetica entre si. As funcoes discriminantes de Anderson identificaram 100% das especies e variedades botânicas estudadas.

Independent Inheritance of Leaf Shape and Main Vein Color in Caladium

The ornamental value of caladium (Caladium ×hortulanum Birdsey) depends primarily on leaf characteristics, including leaf shape and main vein color. Caladium leaf shapes are closely associated with plant growth habit, stress tolerance, and tuber yield; leaf main vein colors are often used for cultivar identification. Thirty-eight crosses were made among 10 cultivars and two breeding lines; their progeny were analyzed to understand the inheritance of leaf shape and main vein color and to determine if there is a genetic linkage between these two traits. Results showed that a single locus with three alleles determined the main vein color in caladium. The locus was designated as V, with alleles Vr, Vw, and Vg for red, white, and green main veins, respectively. The white vein allele was dominant over the green vein allele, but it was recessive to the red vein allele, which was dominant over both white and green vein alleles; thus the dominance order of the alleles is Vr > Vw > Vg. Segregation data indicated that four major red-veined cultivars were heterozygous with the genotype Vr Vg, and that one white-veined cultivar was homozygous and one other white-veined cultivar and one breeding line were heterozygous. The observed segregation data confirmed that the three leaf shapes in caladium were controlled by two co-dominant alleles at one locus, designated as F and f, for fancy and strap leaves, respectively. The skewedness of leaf shape segregation in some of the crosses implied the existence of other factors that might contribute to the formation of leaf shape. Contingency chi-square tests for independence revealed that caladium leaf shape and main vein color were inherited independently. The chi-square tests for goodness-of-fit indicated that the five observed segregation patterns for leaf shape and main vein color fit well to the expected ratio assuming that two co-dominant and three dominant/recessive alleles control leaf shape and main vein color and they are inherited independently.

First Report of Sclerotinia Stem Rot of Chickpea Caused by Sclerotinia sclerotiorum in North Dakota and Washington

Chickpea (Cicer arietinum L.) is cultivated as a rotational crop in the cereal-based production system in the U.S. Pacific Northwest (PNW) and its production is expanding to other northern tier states. During July 2005, symptoms of Sclerotinia stem rot were observed on chickpea cv. Dwelley and Dylan in fields near Spangle, WA and Carrington, ND, respectively, with disease incidence of approximately ≤1% in affected areas at both locations. Symptoms included stem whitening, wilting, and stem breakage. Occasionally, white fluffy mycelium was observed; however, production of sclerotia on infected plants was rarely observed. Sclerotinia sclerotiorum was isolated from diseased stems collected from both states. The isolates produced a ring of sclerotia near the edge of potato dextrose agar (PDA) plates in 7 days and produced neither conidia nor other fruiting bodies in culture after 30 days. PCR amplification of the rDNA internal transcribed spacer region from two representative isolates and subsequent digestion with restriction enzymes, Mbo I and Taq I, produced identical banding patterns to previously identified isolates of S. sclerotiorum from pea from the PNW (2). Chickpea cvs. Dwelley and Spanish White (eight plants of each) were inoculated by fastening mycelial agar plugs from an actively growing colony on PDA onto the stems with Parafilm. Symptoms of stem whitening were observed as early as 2 days after inoculation, and the lesions extended upward and downward from the inoculation site. Wilting and stem breakage were also observed. Control inoculations of four plants of each cultivar with PDA plugs without mycelium produced no visible symptoms. S. sclerotiorum was consistently reisolated from inoculated plants but not from control plants. Chickpea had been grown in the PNW for more than 20 years without any reported incidence of Sclerotinia stem rot although the disease has been reported from Arizona (3) and Asian countries (1). This is likely because of the upright growth habit of the chickpea plant coupled with relatively dry conditions late in the growing season. Previous chickpea cultivars were very susceptible to Ascochyta blight, an early-season disease of chickpea in the PNW that reduced chickpea stands and canopy coverage. Current cultivars possess much improved resistance to Ascochyta blight, allowing greater vegetative growth to occur and creating microenvironmental conditions conducive to Sclerotinia stem rot. In North Dakota, where humid conditions prevail late in the growing season, symptoms of Sclerotinia stem rot had been observed in previous years but had not been documented because of a recent history of chickpea cultivation there. To our knowledge, this is the first report of confirmed Sclerotinia stem rot of chickpea in North Dakota and Washington.

‘BRS Pitanga’: new dry bean variety of the small purple group

BRS Pitanga is a new dry bean [Phaseolus vulgaris] cultivar of the small purple commercial group released for cultivation in the State of Goias and the Federal District in Brazil. The cultivar has an erect plant growth habit, and is resistant to 4 pathotypes (55, 89, 95 and 43) of the causal agents of anthracnose (Colletotrichum lindemuthianum), to rust and to bean common mosaic virus..

Chemical- and Irradiation-induced Mutants of Indica Rice IR64 for Forward and Reverse Genetics

IR64, the most widely grown indica rice in South and Southeast Asia, possesses many positive agronomic characteristics (e.g., wide adaptability, high yield potential, tolerance to multiple diseases and pests, and good eating quality,) that make it an ideal genotype for identifying mutational changes in traits of agronomic importance. We have produced a large collection of chemical and irradiation-induced IR64 mutants with different genetic lesions that are amenable to both forward and reverse genetics. About 60,000 IR64 mutants have been generated by mutagenesis using chemicals (diepoxybutane and ethylmethanesulfonate) and irradiation (fast neutron and gamma ray). More than 38,000 independent lines have been advanced to M4 generation enabling evaluation of quantitative traits by replicated trials. Morphological variations at vegetative and reproductive stages, including plant architecture, growth habit, pigmentation and various physiological characters, are commonly observed in the four mutagenized populations. Conditional mutants such as gain or loss of resistance to blast, bacterial blight, and tungro disease have been identified at frequencies ranging from 0.01% to 0.1%. Results from pilot experiments indicate that the mutant collections are suitable for reverse genetics through PCR-detection of deletions and TILLING. Furthermore, deletions can be detected using oligomer chips suggesting a general technique to pinpoint deletions when genome-wide oligomer chips are broadly available. M4 mutant seeds are available for users for screening of altered response to multiple stresses. So far, more than 15,000 mutant lines have been distributed. To facilitate broad usage of the mutants, a mutant database has been constructed in the International Rice Information System (IRIS; http: //www.iris.irri.org) to document the phenotypes and gene function discovered by users.