Location: Vegetable Research2011 Annual Report
1a. Objectives (from AD-416)
1. Identify or develop tolerant germplasm lines, study the inheritance of tolerance, and utilize genetic differences in herbicide tolerance to improve crop safety and enhance weed management in watermelons and sweetpotato. 2. Develop vegetable crop production systems that utilize competitive crop genotypes and innovative cultural practices to reduce the impact of weeds.
1b. Approach (from AD-416)
Develop watermelon germplasm lines with enhanced tolerance to clomazone herbicide using a conventional plant breeding strategy, study the inheritance of clomazone tolerance, and identify or develop tolerant lines for use in watermelon breeding and as rootstocks for grafted watermelon production. Assess watermelon germplasm for differences in halosulfuron methyl tolerance, and investigate the feasibility of developing tolerant cultivars using conventional plant breeding approaches. Identify sweetpotato clones that differ in clomazone and flumioxazin tolerance, use a recurrent mass selection breeding approach to generate clones with high levels of tolerance and good horticultural characteristics, and make them available for use by sweetpotato breeders. Assess the competitive advantage against weeds of sweetpotato genotypes with more vigorous growth habits in comparison to less competitive conventional cultivars, identify competitive genotypes with good horticultural quality, and evaluate them as component in integrated weed management systems for conventional and organic growers. Evaluate weed management practices utilizing competitive southernpea cultivars as a component in integrated weed management systems for conventional and organic growers. Investigate the impact of poultry and swine litter biochar soil amendment on southernpea and weed growth and on herbicide activity.
3. Progress Report
First and second crosses between tolerant and susceptible wild watermelon lines were completed to assess the heritability of clomazone tolerance. Selected individuals from clomazone susceptible and tolerant plant introduction accessions of the wild watermelon, Citrullus lanatus variety citroides were self pollinated for five successive generations to produce non-segregating clomazone tolerant and susceptible breeding lines. A backcross breeding project to transfer clomazone tolerance from citroides accessions into watermelon was initiated. A germplasm collection of the watermelon rootstock species (Laegenaria siceraria) was evaluated for tolerance to clomazone herbicide. Tolerant and susceptible accessions were identified, and tolerance levels were established using replicated greenhouse concentration-response experiments. Field and greenhouse experiments were conducted to assess differential tolerance to clomazone in broccoli and cabbage varieties. Tolerant and susceptible varieties were identified in both crop groups. A field experiment was conducted to determine the competitiveness of 13 sweetpotato lines against weeds. A field experiment was initiated to assess the competitiveness of determinate, semi-determinate and non-determinate cowpea varieties against weeds and their response to weed interference. A field investigation was initiated in collaboration with the location nematologist to determine the effect of nematode resistant and susceptible cover crop cowpea varieties on nematodes and weeds. Flumioxazin herbicide tolerant and susceptible sweetpotato lines selected in a preliminary screening experiment were re-evaluated for tolerance in a replicated field experiment. This project is the replacement for project 6659-22000-021-00D, BIOLOGICALLY BASED WEED MANAGEMENT FOR VEGETABLE CROPS.