Grain Sorghum Varieties Reaction [Sorghum bicolor (L.) Moench] to Macrophomina phaseolina (Tassi) Gold

摘要

The present study is aimed to evaluate the reaction to M. phaseolina from seven commercial and experimental sorghum varieties and two hybrids. Sorghum stalk rot caused by M. phaseolina is the most important sorghum disease in northern Tamaulipas, Mexico because when drought and high temperatures are prevalent, it causes up lo 100% losses in grain yield. This study was established in Rio Bravo, Tamaulipas, Mexico during 2006 autumn-winter cycles with a pre-planting irrigation, and in 2007 under rainfall conditions in a randomized block design with four replications. Sorghum plants were inoculated with Af. phaseolina using the toothpick technique, as proposed by Edmunds in 1964. There were significant differences among years and, in 2006 there was a greater lesion length (23.1 cm) than in 2007 experiment (17.5 cm). This was related to higher temperatures and a more severe drought, present in 2006 at sorghum flowering and grain filling stages. Results indicated that in both years, Amarillo Precoz variety (9.2 cm) was significantly more tolerant than S-23 (15.5 cm), VAR-9 (19.6 cm), Mazatlán 16 (21.6 cm) and Perla 101 varieties (23.2 cm) and RB-3030 (17.3 cm) hybrid. Furthermore, Amarillo Precoz revealed a similar M. phaseolina tolerance than Dulce (12.1 cm), Costeno 201 (14.2 cm) and Asgrow ámbar. There was no correlation between lesion length and grain yield; hybrids showed a greater yield than varieties. Amarillo Precoz was selected as a source of tolerance to M. phaseolina and would be used asa variety or hybri d parental line.