Embrapa launches rootstock for nematode-resistant guava

After almost ten years of research, Embrapa provides the first efficient technology for controlling root-knot nematode, which is currently the main challenge facing guava cultivation in the country. The BRS Guaraçá cultivar is a hybrid plant, which mixes characteristics of guava and araçazeiro, to be used as a rootstock. It will be launched during the ceremony celebrating the Company's 46th anniversary, on April 24th, in Brasília-DF.

According to Embrapa Semiarid researcher Carlos Antônio Fernandes Santos, “the technology is the best option for combating guava nematosis, as it has demonstrated resistance to the pathogen and high compatibility with the most important commercial varieties. Furthermore, it does not present high costs for obtaining seedlings, and is agronomically and environmentally safe and viable”.

The cultivar solves a national problem, as the pathogen Meloidogyne enterolobii It has already been registered in areas of 19 Brazilian states. In the São Francisco Valley (Pernambuco and Bahia), one of the main fruit production centers in the country, its destructive presence in guava orchards was identified in 2001, decimating more than half of the cultivated area in the region.

The origin

Until now, the strategies sought by research groups from different parts of the country to solve this serious phytosanitary problem involved biological control methods, integrated management and application of insecticides, presenting limited or inefficient results. The use of araçazeiro as a rootstock was also tested, but with low compatibility with guava cultivars.

The group of researchers from Embrapa Semárido, also formed by José Mauro da Cunha e Castro and José Egídio Flori, then decided to invest in a pioneering study to obtain hybrids that had resistance to the nematode characteristic of the araçazeiro (Psidium guineense) and the compatibility with commercial varieties provided by the guava tree (P. guajava).

Thus, BRS Guaraçá was developed through genetic improvement, from crossings of two species of Psidium, with a guava tree as its mother plant and an araçazeiro as its parent plant. The materials used were selected after evaluating a hundred genotypes of araçás resistant to the parasite, collected from North to South of the country and also in the Caribbean. A similar procedure was carried out with guava trees, however all were completely susceptible to the pathogen.

The hybrid resulting from this crossing has 50% of the guava genome, minimizing incompatibility with canopy cultivars, including the low size of the araçazeiro. “BRS Guaraçá has a plant with great vigor, which makes it ideal for use as a rootstock”, explains Carlos Antônio.

Reviews  

After obtaining the hybrid, resistance to the nematode and the compatibility of the rootstock with guava cultivars were tested through artificial inoculation in a controlled environment and field evaluations. In tests carried out at the Bebedouro Experimental Field, at Embrapa Semiárido (Petrolina-PE), BRS Guaraçá showed a complete absence of the nematode in its infective phase, five years after transplanting and even in the endemic presence of the pathogen in the soil. In producer areas, studies have identified a 500 times greater number of the nematode in the free-standing plants, compared to the hybrid.

In the evaluations of the grafting of BRS Guaraçá with the main commercial varieties of guava tree – “Paluma” and “Pedro Sato” –, no exudations, cracks in the stem of the grafted plants or differences in diameter at the grafting site were observed, indicating their compatibility. The grafted cultivars produced around 40 tons of fruit per hectare, in harvests carried out 30 months after transplanting, with plant heights exceeding 2 meters.

How to get  

Embrapa is currently in the licensing phase and making the material available to nurseries hired, through a notice, to commercialize the BRS Guaraçá cultivar. The list and contact details of licensees, as well as other information about the rootstock, are available at here.

Click here to access photos of BRS Guaraçá.