Phenotypic variation of agronomic traits among coyote gourd accessions and their progeny

Abstract

As a prelude to domestication efforts, variation of agronomic traits was determined among accessions of the polytypic, xerophytic cucurbit, coyote gourd [Cucurbita digitata subsp. digitata (DIG), palmata (PAL), cylindrata (CYL), and cordata (COR)] and among and within their progeny. Oil content in 60 accession seed lots (x = 27.8%, CV 21.4%) was more variable than protein content (x = 33.1%, CV = 13.5%). Punicic acid (c,t,c-9,ll,13-octadecatrienoic acid) levels in seed oils were also variable (x = 12.0%, CV = 20.6%) among accession seed lots. Substantial differences among and within subspecies were noted in 40 progeny lines for fruit/plant (x = 55.2, CV = 47.5%), seed wt/plant (x = 0.89 kg, CV = 51.1%), seed wt/fruit (x = 17.4 g, CV = 39.8%), seed no./fruit (x = 356, CV= 30.8%), 100-seed wt (x = 4.8 g, CV = 21.6%) and fruit diameter (x = 77 mm, CV 4.8%). Correlations among parameters suggested selection for fruit/plant to be the most effective primary strategy for seed yield improvement, but among high fruit-yielders, selection for seed wt/fruit was also important. The two subspecies PAL and CYL exhibited superior seed wts/plant. CYL types matured high fruit-loads, but their fruits were smaller and contained a smaller number of lighter seed than PAL or PAL hybrids. In contrast, PAL and PAL hybrids displayed lower fruit-yields/ plant but their fruits were larger and contained higher seed wts/fruit than their CYL counterparts. Root wt/plant was also variable (x = 1.55 kg, CV = 63.2%). Roots of DIG were larger and less branched than those of other subspecies. Proximate and liquid Chromatographic analyses of selected accession seed lots and controlled crosses failed to reveal advantages for the inclusion of specific types in a breeding program for the development of high oil or high/low punicic acid lines.