Organography of greenhouse and field accessions of wild Arachisspecies (section Arachis)

<div><p>ABSTRACT Peanut or groundnut (Arachis hypogaea L.) is a globally important oilseed crop, with important nutritional qualities, and a rich source of amino acids and protein. Another 80 species have been described in the genus Arachis, 64 of which are found in Brazil, and even though their morphology and agronomic traits remain largely unknown, they have been cultivated for forage and for landscaping and have great potential for breeding with cultivated peanut. Thus, the morphological characterization of wild Arachis species is essential for their conservation and use. In this study, we present a morphological and agronomic characterization of 29 diploid accessions of eleven wild Arachis species and one of the tetraploid A. monticola (section Arachis) with A and B genomes and determine their intra- and interspecific variability in greenhouse and field conditions. In total, 35 morphological descriptors were developed a priori from greenhouse accessions in the first crop year and used in field accessions in the second crop year. Significant differences in descriptors compiled in the greenhouse and the field support the use of different descriptors for different experimental conditions. PCA analysis showed that the distribution of accessions accorded with the taxonomy of species. The ten morphological descriptors that were important in differentiating section Arachis accessions were seed length, lateral branch length, right apical leaflet length, right apical leaflet width, height and diameter of main stem, branch color, standard petal base color, number of flowers, and presence of bristles on rachis.</p></div

Recombinants from the crosses between amphidiploid and cultivated peanut (<i>Arachis hypogaea</i>) for pest-resistance breeding programs

<div><p>Peanut is a major oilseed crop worldwide. In the Brazilian peanut production, silvering thrips and red necked peanut worm are the most threatening pests. Resistant varieties are considered an alternative to pest control. Many wild diploid <i>Arachis</i> species have shown resistance to these pests, and these can be used in peanut breeding by obtaining hybrid of A and B genomes and subsequent polyploidization with colchicine, resulting in an AABB amphidiploid. This amphidiploid can be crossed with cultivated peanut (AABB) to provide genes of interest to the cultivar. In this study, the sterile diploid hybrids from <i>A</i>. <i>magna</i> V 13751 and <i>A</i>. <i>kempff-mercadoi</i> V 13250 were treated with colchicine for polyploidization, and the amphidiploids were crossed with <i>A</i>. <i>hypogaea</i> cv. IAC OL 4 to initiate the introgression of the wild genes into the cultivated peanut. The confirmation of the hybridity of the progenies was obtained by: (1) reproductive characterization through viability of pollen, (2) molecular characterization using microsatellite markers and (3) morphological characterization using 61 morphological traits with principal component analysis. The diploid hybrid individual was polyploidized, generating the amphidiploid An 13 (<i>A</i>. <i>magna</i> V 13751 x <i>A</i>. <i>kempff-mercadoi</i> V 13250)^4x. Four F₁ hybrid plants were obtained from IAC OL 4 × An 13, and 51 F₂ seeds were obtained from these F₁ plants. Using reproductive, molecular and morphological characterizations, it was possible to distinguish hybrid plants from selfed plants. In the cross between <i>A</i>. <i>hypogaea</i> and the amphidiploid, as the two parents are polyploid, the hybrid progeny and selves had the viability of the pollen grains as high as the parents. This fact turns the use of reproductive characteristics impossible for discriminating, in this case, the hybrid individuals from selfing. The hybrids between <i>A</i>. <i>hypogaea</i> and An 13 will be used in breeding programs seeking pest resistance, being subjected to successive backcrosses until recovering all traits of interest of <i>A</i>. <i>hypogaea</i>, keeping the pest resistance.</p></div

Microsatellite markers used in this study.

<p>Microsatellite markers used in this study.</p

Pollen grains of the hybrid IAC OL4 x An 13.

<p>A) Pollen grains stained with 2% carmine acetic acid with glycerin. B) Pollen grains stained with 0.25% tetrazolium. Arrows indicate inviable grains. 100 X magnification under an optical microscope.</p

Progeny of IAC OL4 x An 13 under attack by mites.

<p>The blue arrow indicates the plants resistant to mite, result from hybridization. The red arrow indicates the plants susceptible to mite, a result from selfing.</p

Comparison in the number of lateral branches between plants from.

<p>(A) hybridization and (B) selfing.</p

Order of descriptors that contributed most to the morphological variation observed in the principal component 1 (Prin 1) of the Principal Component Analysis of all the individuals evaluated in this work

<p>Order of descriptors that contributed most to the morphological variation observed in the principal component 1 (Prin 1) of the Principal Component Analysis of all the individuals evaluated in this work</p

Biplot graph resulting from the cross between IAC OL4 x An 13, obtained by Principal Component Analysis considering the 61 descriptors for the principal components 1 and 2.

<p>Triangle indicates female parents V 13751 (13) and IAC OL4 (11); circles, male parents V 13250 (14) and An 13 (12); and representing the progenies, square indicates the hybrid plants V 13751 x V 13250 (15) and IAC OL4 x An 13(1 to 4), and, diamonds, the plants derived from selfing IAC OL4 x An 13 (5 to 10).</p

Parents and progeny of IAC OL4 x An 13 under attack by mites.

<p>The blue arrow represents the plants resistant to mite (An 13 and hybrid). The red arrow represents the plants susceptible to mite (IAC OL4 and selfed).</p

Viability of pollen grains of 22 individuals analyzed by staining

<p>Viability of pollen grains of 22 individuals analyzed by staining</p