Indirect morpho-physiological changes associated with selection programs for increased yield in wild species of Lesquerella

GOZALEZ PALEO, L, RAVETTA, D.A.

Chilla, Chile

Congreso; AAIC 21st Annual Meeting. International Conference: The next generation of Industrial Crops, Processes and Products. Termas de Chillán, Chillán, Chile. 14-19 November 2009.; 2009

Association for the Advancement of Industrial Crops, USA

Higher yield of improved cultivars generally comes from the re-partitioning of photo-assimilates towards an increase in harvest index (H.I.). Thus, selection based on seed-yield tends to be linked to reduced drought tolerance, plant defence, and plant longevity. As a result, the improvement of new crops (particularly targeted for arid lands) carries an implicit increase in sensitivity to changes in the environmental quality (i.e. reduced yield stability), similar to what has been found in conventional crops. Lesquerella is considered a promising seed-oil crop, and annual and perennial species are included in domestication programs. Ideally, breeding programs of crops targeted for arid lands should strive for cultivars with lower but more stable yields than traditional crops, and retain some of the basic traits found in their wild relatives that provide adaptation for growth and survival in low-resource environments. A better understanding of the relationship between seed-yield and drought-tolerance related traits is key to defining new criteria of selection in crops specifically targeted to arid land. This field study was conducted to assess the effects of breeding for increased seed-yield on traits related to drought tolerance and growth, in annual (L. gracilis y L. angustifolia) and perennial (L. pinetorum y L. mendocina) species of Lesquerella. In a completely aleatorized design with two factors (species *selection), we compared growth, morpho-physiological and allocation traits, and seed-yield in selected (three selection cycles by seed-yield) and wild (bulk collections from native stands). We found a change in the seasonal pattern of growth in the selected accessions (SA) of Lesquerella. The SA of the two annual species and L. mendocina, had a lower relative growth rate in autumn and winter (coincident with the vegetative phase, RGRveg) compared to non-selected accessions (NSA), which was linked to a decrease assimilation rate (A, p<0.01), and a lower allocation to leaf (LMR, p<0,05) and leaf area ratio (LAR, p<0,05). The SA of L. pinetorum showed a higher RGRveg related to higher A (p<0,01) and specific leaf area (SLA, p<0,05). In all four species proportional allocation to storage (TNC) during the vegetative stage was lower in SA (p<0,01), with no changes in allocations to roots (RMR). When we compared SA vs. NSA (all species) in the reproductive phase (spring-summer) we found higher RGR in SA, related to higher SLA (p<0,01), A (p<0,05), gs (p<0,05) and WUE (p<0,01), and lower proportional TNC at maturity in the SA of perennials (p<0,01). Only in L. gracilis this pattern of growth resulted in a higher RGR total and total biomass of SA. The higher total biomass of SA of L. pinetorum was consequence of a larger growth cycle (RGRtotal was not changed). In L. angustifolia and L. pinetorum the higher seed-yield of SA was linked to higher H.I. In three species the flowering was early in selected than in wild accessions (p<0,01), only in L. pinetorum SA was a later flowering time than NSA. Selection for seed-yield resulted in changes in structural traits (lower RMR and TNC, higher SLA) which explain the increase in yield but should result in lower yield stability in drought prone environments. On the other hand, the higher seed-yield was linked to changes in functional traits such as increased A without a changes in E, which resulted in higher water use efficiency (WUE) in the reproductive phase. The lower TNC at maturity of SA in perennials could compromise the longevity of these species