Resistance to thrips (Enneothrips flavens) in wild and amphidiploid Arachis species.

Thrips (Enneothrips flavens) is a pest that causes severe damage and yield losses to peanut crop if not properly controlled. The main control method currently used by farmers is bi-weekly application of insecticides during crop development, which, in addition to its toxicity, is very costly. Thus, new sources of resistance must be identified in order to reduce the use of insecticides and effectively manage the pest. This study aimed to evaluate the occurrence and symptoms of E. flavens infestations in 12 accessions of 10 wild species of Arachis and nine amphidiploids, as well as to compare their morphoagronomic characteristics to those of commercial cultivars. To this end, we conducted experiments during two summer seasons, using a randomized block design with four replications. We conducted evaluations of the severity of infestation, noting visual symptoms of E. flavens and morphological and reproductive characteristics of the Arachis plants. Results indicated that wild accessions V 7635 (A. vallsii), V 13250 (A. kempff-mercadoi), K 9484 (A. batizocoi), Wi 1118 (A. williamsii), V 14167 (A. duranensis) and V 13751 (A. magna) are the most promising for obtaining useful new amphidiploids. Among the amphidiploids, An 12 (A. batizocoi x A. kempff-mercadoi)4x, An 9 (A. gregoryi x A. stenosperma) 4x, and An 8 (A. magna x A. cardenasii)4x showed high level of resistance to E. flavens. The identified thrips resistant wild and amphidiploid Arachis species may be used in future breeding program to produce thrips resistant peanut cultivars.

Identification of Fungus Resistant Wild Accessions and Interspecific Hybrids of the Genus Arachis.

Peanut, Arachis hypogaea L., is a protein-rich species consumed worldwide. A key improvement to peanut culture involves the development of cultivars that resist fungal diseases such as rust, leaf spot and scab. Over three years, we evaluated fungal resistance under field conditions of 43 wild accessions and three interspecific hybrids of the genus Arachis, as well as six A. hypogaea genotypes. In the first year, we evaluated resistance to early and late leaf spot, rust and scab. In the second and third years, we evaluated the 18 wild species with the best resistance scores and control cultivar IAC Caiapó for resistance to leaf spot and rust. All wild accessions displayed greater resistance than A. hypogaea but differed in their degree of resistance, even within the same species. We found accessions with as good as or better resistance than A. cardenasii, including: A. stenosperma (V15076 and Sv 3712), A. kuhlmannii (V 6413), A. kempff-mercadoi (V 13250), A. hoehnei (KG 30006), and A. helodes (V 6325). Amphidiploids and hybrids of A. hypogaea behaved similarly to wild species. An additional four accessions deserve further evaluation: A. magna (V 13751 and KG 30097) and A. gregoryi (V 14767 and V 14957). Although they did not display as strong resistance as the accessions cited above, they belong to the B genome type that is crucial to resistance gene introgression and pyramidization in A. hypogaea.