Identification Of AFLP Markers Linked To Resistance To Late Leaf Spot And Analysis Of Genetic Diversity Among Cultivated Peanut (Arachis Hypogaea L.) Germplasm From Sichuan & Chongqing

Cultivated peanut (Arachis hypogaea L.) is an important oilseed and cash crop worldwide. It is grown in nearly 100 countries and is a major source of plant protein and cooking oil in many developing countries. China is one of the major producers and consumer of peanut in the world. Sichuan and Chongqing are one of the major peanut production regions in China. Peanut diseases including late leaf spot (LLS) caused by Phaeoisariopsis personata (Berk & Curt) V. Arx. have been important constraints to production for decades in the region. Development of disease-resistant cultivars is the most effective control strategy. The main objectives of this investigation were to 1) identify AFLP markers linked to late leaf spot resistance, 2) verify the identified AFLP markers against different resistant genotypes, 3) select resistant lines for further breeding programs, and 4) assess molecular diversity and phenotypic diversity for agronomic traits among the major peanut germplasm accessions from Sichuan & Chongqing region.A peanut line highly resistant to LLS derived from an interspecific hybridization cross, ICGV 86699, was used to identify AFLP markers for LLS resistance. The resistance to LLS in ICGV 86699 was found to be controlled by a single recessive gene based on the resistance identification and analysis of segregation in the F₂ population of Zhonghua No.5 × ICGV 86699. Bulked segregant analysis (BSA) and amplified fragment length polymorphism (AFLP) analysis were employed to identify DNA markers linked to LLS resistance based on the segregating F₂ population of the cross. Three AFLP makers, E35/M51, E37/M48 and E41/M47, linked to the LLS-resistant gene were identified. The three makers were also linked each other on same linkage group. The map distance between the markers and the resistant gene were 7.40, 7.40, and 8.67 cM, respectively. This is the first report on the identification of AFLP markers closely linked to LLS resistance in peanut.The genetic diversity of 43 breeding lines and released cultivars representing four botanical varieties of two subspecies was assessed by clustering analysis of AFLP markers and phenotyping of eight agronomic traits. The results of clustering based on AFLP were basically consistent with that from phenotypic analyses. The genetic distances within var. vulgaris and var. hirsuta were small, while the distances within var. hypogaea and the improved breeding lines derived from crosses involving genotypes belonging to different subspecies as parents were the large. The relationship between var. hirsuta and var. hypogaea was much close, while that between var. vulgaris and var. hypogaea was most alienative. The genetic varition detected among the major cultivars were very limited. It is necessary to exploit native germplasm and introduce the exotic germplasm in peanut improvement in Sichuan & Chongqing region.